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The Sun is the star at the center of the Solar System. [1]

548 relations: Absolute magnitude, Abundance of the chemical elements, Aditya-L1, Adjective, Advanced Composition Explorer, AIP Conference Proceedings, Akhenaten, Al-Battani, Albedo, Albert Einstein, Alfvén wave, Alpha particle, Amarna Period, Amaterasu, American Geophysical Union, American Philosophical Society, Anaxagoras, Ancient Egypt, Ancient Greece, Ancient Greek religion, Angular diameter, Angular momentum, Annual Review of Astronomy and Astrophysics, Antiseptic, Antisolar point, Apollo, Apollo Telescope Mount, Apparent magnitude, Apsis, Archean, Archimedean spiral, Aristarchus of Samos, Arthur Eddington, Asteroid belt, Astrolabe, Astronomical spectroscopy, Astronomical unit, Astronomische Nachrichten, Astronomy, Astronomy & Astrophysics, Astronomy & Geophysics, Astronomy in the medieval Islamic world, Asymptotic giant branch, Aten, Atmosphere of Earth, Atmospheric entry, Attenuation, Aurora, Australian Broadcasting Corporation, Averroes, ..., Avicenna, Axial tilt, Aztecs, 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Absolute magnitude

Absolute magnitude is a measure of the luminosity of a celestial object, on a logarithmic astronomical magnitude scale.

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Abundance of the chemical elements

The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment.

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Aditya-L1

Aditya (publisher) or Aditya-L1 is a spacecraft whose mission is to study the Sun.

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Adjective

In linguistics, an adjective (abbreviated) is a describing word, the main syntactic role of which is to qualify a noun or noun phrase, giving more information about the object signified.

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Advanced Composition Explorer

Advanced Composition Explorer (ACE) is a NASA Explorers program Solar and space exploration mission to study matter comprising energetic particles from the solar wind, the interplanetary medium, and other sources.

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AIP Conference Proceedings

AIP Conference Proceedings is a serial published by the American Institute of Physics since 1970.

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Akhenaten

Akhenaten (also spelled Echnaton, Akhenaton, Ikhnaton, and Khuenaten; meaning "Effective for Aten"), known before the fifth year of his reign as Amenhotep IV (sometimes given its Greek form, Amenophis IV, and meaning "Amun Is Satisfied"), was an ancient Egyptian pharaoh of the 18th Dynasty who ruled for 17 years and died perhaps in 1336 BC or 1334 BC.

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Al-Battani

Abū ʿAbd Allāh Muḥammad ibn Jābir ibn Sinān al-Raqqī al-Ḥarrānī aṣ-Ṣābiʾ al-Battānī (Arabic: محمد بن جابر بن سنان البتاني) (Latinized as Albategnius, Albategni or Albatenius) (c. 858 – 929) was an Arab astronomer, astrologer, and mathematician.

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Albedo

Albedo (albedo, meaning "whiteness") is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body (e.g. a planet like Earth).

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Albert Einstein

Albert Einstein (14 March 1879 – 18 April 1955) was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics).

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Alfvén wave

In plasma physics, an Alfvén wave, named after Hannes Alfvén, is a type of magnetohydrodynamic wave in which ions oscillate in response to a restoring force provided by an effective tension on the magnetic field lines.

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Alpha particle

Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus.

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Amarna Period

The Amarna Period was an era of Egyptian history during the later half of the Eighteenth Dynasty when the royal residence of the pharaoh and his queen was shifted to Akhetaten ('Horizon of the Aten') in what is now Amarna.

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Amaterasu

,, or is a deity of the Japanese myth cycle and also a major deity of the Shinto religion.

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American Geophysical Union

The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of geophysicists, consisting of over 62,000 members from 144 countries.

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American Philosophical Society

The American Philosophical Society (APS), founded in 1743 and located in Philadelphia, is an eminent scholarly organization of international reputation that promotes useful knowledge in the sciences and humanities through excellence in scholarly research, professional meetings, publications, library resources, and community outreach.

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Anaxagoras

Anaxagoras (Ἀναξαγόρας, Anaxagoras, "lord of the assembly"; BC) was a Pre-Socratic Greek philosopher.

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Ancient Egypt

Ancient Egypt was a civilization of ancient Northeastern Africa, concentrated along the lower reaches of the Nile River - geographically Lower Egypt and Upper Egypt, in the place that is now occupied by the countries of Egypt and Sudan.

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Ancient Greece

Ancient Greece was a civilization belonging to a period of Greek history from the Greek Dark Ages of the 13th–9th centuries BC to the end of antiquity (AD 600).

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Ancient Greek religion

Ancient Greek religion encompasses the collection of beliefs, rituals, and mythology originating in ancient Greece in the form of both popular public religion and cult practices.

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Angular diameter

The angular diameter, angular size, apparent diameter, or apparent size is an angular measurement describing how large a sphere or circle appears from a given point of view.

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Angular momentum

In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational equivalent of linear momentum.

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Annual Review of Astronomy and Astrophysics

The Annual Review of Astronomy and Astrophysics is an annual peer reviewed scientific journal published by Annual Reviews.

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Antiseptic

Antiseptics (from Greek ἀντί anti, "against" and σηπτικός sēptikos, "putrefactive") are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction.

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Antisolar point

The antisolar point is the abstract point on the celestial sphere directly opposite of the Sun from an observer's perspective.

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Apollo

Apollo (Attic, Ionic, and Homeric Greek: Ἀπόλλων, Apollōn (Ἀπόλλωνος); Doric: Ἀπέλλων, Apellōn; Arcadocypriot: Ἀπείλων, Apeilōn; Aeolic: Ἄπλουν, Aploun; Apollō) is one of the most important and complex of the Olympian deities in classical Greek and Roman religion and Greek and Roman mythology.

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Apollo Telescope Mount

The Apollo Telescope Mount, or ATM, was a solar observatory attached to Skylab, the first American space station.

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Apparent magnitude

The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.

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Apsis

An apsis (ἁψίς; plural apsides, Greek: ἁψῖδες) is an extreme point in the orbit of an object.

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Archean

The Archean Eon (also spelled Archaean or Archæan) is one of the four geologic eons of Earth history, occurring (4 to 2.5 billion years ago).

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Archimedean spiral

The Archimedean spiral (also known as the arithmetic spiral) is a spiral named after the 3rd century BC Greek mathematician Archimedes.

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Aristarchus of Samos

Aristarchus of Samos (Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios; c. 310 – c. 230 BC) was an ancient Greek astronomer and mathematician who presented the first known model that placed the Sun at the center of the known universe with the Earth revolving around it (see Solar system).

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Arthur Eddington

Sir Arthur Stanley Eddington (28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician of the early 20th century who did his greatest work in astrophysics.

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Asteroid belt

The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter.

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Astrolabe

An astrolabe (ἀστρολάβος astrolabos; ٱلأَسْطُرلاب al-Asturlāb; اَختِرِیاب Akhteriab) is an elaborate inclinometer, historically used by astronomers and navigators to measure the inclined position in the sky of a celestial body, day or night.

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Astronomical spectroscopy

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects.

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Astronomical unit

The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.

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Astronomische Nachrichten

Astronomische Nachrichten (Astronomical Notes), one of the first international journals in the field of astronomy, was founded in 1821 by the German astronomer Heinrich Christian Schumacher.

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Astronomy

Astronomy (from ἀστρονομία) is a natural science that studies celestial objects and phenomena.

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Astronomy & Astrophysics

Astronomy & Astrophysics is a peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics.

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Astronomy & Geophysics

Astronomy & Geophysics (A&G) is a scientific journal and trade magazine published on behalf of the Royal Astronomical Society (RAS) by Oxford University Press.

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Astronomy in the medieval Islamic world

Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9th–13th centuries), and mostly written in the Arabic language.

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Asymptotic giant branch

The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars.

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Aten

Aten (also Aton, Egyptian jtn) is the disk of the sun in ancient Egyptian mythology, and originally an aspect of the god Ra.

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Atmosphere of Earth

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.

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Atmospheric entry

Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet or natural satellite.

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Attenuation

In physics, attenuation or, in some contexts, extinction is the gradual loss of flux intensity through a medium.

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Aurora

An aurora (plural: auroras or aurorae), sometimes referred to as polar lights, northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in the Earth's sky, predominantly seen in the high-latitude regions (around the Arctic and Antarctic).

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Australian Broadcasting Corporation

The Australian Broadcasting Corporation (ABC) founded in 1929 is Australia's national broadcaster, funded by the Australian Federal Government but specifically independent of Government and politics in the Commonwealth.

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Averroes

Ibn Rushd (ابن رشد; full name; 1126 – 11 December 1198), often Latinized as Averroes, was an Andalusian philosopher and thinker who wrote about many subjects, including philosophy, theology, medicine, astronomy, physics, Islamic jurisprudence and law, and linguistics.

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Avicenna

Avicenna (also Ibn Sīnā or Abu Ali Sina; ابن سینا; – June 1037) was a Persian polymath who is regarded as one of the most significant physicians, astronomers, thinkers and writers of the Islamic Golden Age.

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Axial tilt

In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane.

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Aztecs

The Aztecs were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521.

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Babcock Model

The Babcock Model describes a mechanism which can explain magnetic and sunspot patterns observed on the Sun.

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Babylonian astronomy

The history of astronomy in Mesopotamia, and the world, begins with the Sumerians who developed the earliest writing system—known as cuneiform—around 3500–3200 BC.

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Bible

The Bible (from Koine Greek τὰ βιβλία, tà biblía, "the books") is a collection of sacred texts or scriptures that Jews and Christians consider to be a product of divine inspiration and a record of the relationship between God and humans.

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Big Bang nucleosynthesis

In physical cosmology, Big Bang nucleosynthesis (abbreviated BBN, also known as primordial nucleosynthesis, arch(a)eonucleosynthesis, archonucleosynthesis, protonucleosynthesis and pal(a)eonucleosynthesis) refers to the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, 1H, having a single proton as a nucleus) during the early phases of the Universe.

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Binoculars

Binoculars or field glasses are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.

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Black body

A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.

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Black dwarf

A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light.

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British Journal of Ophthalmology

The British Journal of Ophthalmology is a peer-reviewed medical journal covering all aspects of ophthalmology.

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Bulletin of the Astronomical Society of India

The Bulletin of the Astronomical Society of India is the official quarterly peer-reviewed scientific journal of the Astronomical Society of India established in 1973 and published until the end of 2014.

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Cairo University

Cairo University (جامعة القاهرة, known as the Egyptian University from 1908 to 1940, and King Fuad I University from 1940 to 1952) is Egypt's premier public university.

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Calendar

A calendar is a system of organizing days for social, religious, commercial or administrative purposes.

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California Institute of Technology

The California Institute of Technology (abbreviated Caltech)The university itself only spells its short form as "Caltech"; other spellings such as.

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Cambridge

Cambridge is a university city and the county town of Cambridgeshire, England, on the River Cam approximately north of London.

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Cambridge University Press

Cambridge University Press (CUP) is the publishing business of the University of Cambridge.

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Candela per square metre

The candela per square metre (cd/m2) is the derived SI unit of luminance.

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Capital punishment

Capital punishment, also known as the death penalty, is a government-sanctioned practice whereby a person is put to death by the state as a punishment for a crime.

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Carbon

Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.

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Carbon dioxide

Carbon dioxide (chemical formula) is a colorless gas with a density about 60% higher than that of dry air.

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Carbon monoxide

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air.

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Cataract

A cataract is a clouding of the lens in the eye which leads to a decrease in vision.

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Cecilia Payne-Gaposchkin

Cecilia Helena Payne-Gaposchkin (May 10, 1900 – December 7, 1979) was a British–American astronomer and astrophysicist who, in 1925, proposed in her Ph.D. thesis an explanation for the composition of stars in terms of the relative abundances of hydrogen and helium.

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Chariot

A chariot is a type of carriage driven by a charioteer using primarily horses to provide rapid motive power.

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Chemical element

A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).

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Chemosynthesis

In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight, as in photosynthesis.

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Chichen Itza

Chichen Itza, Chichén Itzá, often with the emphasis reversed in English to; from Chi'ch'èen Ìitsha' (Barrera Vásquez et al., 1980.) "at the mouth of the well of the Itza people" was a large pre-Columbian city built by the Maya people of the Terminal Classic period.

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Chinese astronomy

Astronomy in China has a long history, beginning from the Shang Dynasty (Chinese Bronze Age).

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Christianity

ChristianityFrom Ancient Greek Χριστός Khristós (Latinized as Christus), translating Hebrew מָשִׁיחַ, Māšîăḥ, meaning "the anointed one", with the Latin suffixes -ian and -itas.

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Chromosphere

The chromosphere (literally, "sphere of color") is the second of the three main layers in the Sun's atmosphere and is roughly 3,000 to 5,000 kilometers deep.

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CIE 1931 color space

The CIE 1931 color spaces were the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision.

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Circumference

In geometry, the circumference (from Latin circumferentia, meaning "carrying around") of a circle is the (linear) distance around it.

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Classical Philology (journal)

Classical Philology is a peer-reviewed academic journal established in 1906.

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Classical planet

In classical antiquity, the seven classical planets are the seven non-fixed astronomical objects in the sky visible to the naked eye: Mars, Jupiter, Venus, Saturn, Mercury, the Sun, and the Moon.

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Climatology

Climatology (from Greek κλίμα, klima, "place, zone"; and -λογία, -logia) or climate science is the scientific study of climate, scientifically defined as weather conditions averaged over a period of time.

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CNN

Cable News Network (CNN) is an American basic cable and satellite television news channel and an independent subsidiary of AT&T's WarnerMedia.

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CNO cycle

The CNO cycle (for carbon–nitrogen–oxygen) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction.

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Cobalt

Cobalt is a chemical element with symbol Co and atomic number 27.

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Comet

A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing.

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Compost

Compost is organic matter that has been decomposed in a process called composting.

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Computer simulation

Computer simulation is the reproduction of the behavior of a system using a computer to simulate the outcomes of a mathematical model associated with said system.

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Convection

Convection is the heat transfer due to bulk movement of molecules within fluids such as gases and liquids, including molten rock (rheid).

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Coriolis force

In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame.

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Corona

A corona (Latin, 'crown') is an aura of plasma that surrounds the Sun and other stars.

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Coronagraph

A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved.

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Coronal hole

Coronal holes are areas where the Sun's corona is colder, hence darker, and has lower-density plasma than average because there is lower energy and gas levels.

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Coronal mass ejection

A coronal mass ejection (CME) is a significant release of plasma and magnetic field from the solar corona.

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Cosmic microwave background

The cosmic microwave background (CMB, CMBR) is electromagnetic radiation as a remnant from an early stage of the universe in Big Bang cosmology.

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Cosmic ray

Cosmic rays are high-energy radiation, mainly originating outside the Solar System and even from distant galaxies.

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Crater (constellation)

Crater is a small constellation in the Southern Celestial Hemisphere.

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CRC Press

The CRC Press, LLC is a publishing group based in the United States that specializes in producing technical books.

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Cubic metre

The cubic metre (in British English and international spelling as used by the International Bureau of Weights and Measures) or cubic meter (in American English) is the SI derived unit of volume.

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Current Science

Current Science is an English-language peer-reviewed multidisciplinary scientific journal.

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Cygnus (constellation)

Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan.

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Declination

In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle.

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Degenerate matter

Degenerate matter is a highly dense state of matter in which particles must occupy high states of kinetic energy in order to satisfy the Pauli exclusion principle.

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Deity

A deity is a supernatural being considered divine or sacred.

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Dendrochronology

Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in order to analyze atmospheric conditions during different periods in history.

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Density

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume.

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Diffuse sky radiation

Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere.

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Dung beetle

Dung beetles are beetles that feed partly or exclusively on feces (dung).

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Dutch language

The Dutch language is a West Germanic language, spoken by around 23 million people as a first language (including the population of the Netherlands where it is the official language, and about sixty percent of Belgium where it is one of the three official languages) and by another 5 million as a second language.

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Dwarf planet

A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite.

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Earth

Earth is the third planet from the Sun and the only astronomical object known to harbor life.

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Earth mass

Earth mass (where ⊕ is the standard astronomical symbol for planet Earth) is the unit of mass equal to that of Earth.

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Earth radius

Earth radius is the approximate distance from Earth's center to its surface, about.

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East Semitic languages

The East Semitic languages are one of six current divisions of the Semitic languages, the others being Northwest Semitic, Arabian, Old South Arabian (also known as Sayhadic), Modern South Arabian, and Ethio-Semitic.

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Ecliptic

The ecliptic is the circular path on the celestial sphere that the Sun follows over the course of a year; it is the basis of the ecliptic coordinate system.

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Effective temperature

The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation.

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Egypt

Egypt (مِصر, مَصر, Khēmi), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia by a land bridge formed by the Sinai Peninsula.

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El Castillo, Chichen Itza

El Castillo (Spanish for "the castle"), also known as the Temple of Kukulcan (or sometimes Kukulkan), is a Mesoamerican step-pyramid that dominates the center of the Chichen Itza archaeological site in the Mexican state of Yucatán.

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Elagabalus

Elagabalus, also known as Heliogabalus (Marcus Aurelius Antoninus Augustus; 203 – 11 March 222), was Roman emperor from 218 to 222.

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Electric power

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.

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Electromagnetic spectrum

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

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Elliptic orbit

In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0.

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Encyclopedia Astronautica

The Encyclopedia Astronautica is a reference web site on space travel.

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Endothermic process

The term endothermic process describes the process or reaction in which the system absorbs energy from its surroundings, usually in the form of heat.

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Energy

In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.

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Equator

An equator of a rotating spheroid (such as a planet) is its zeroth circle of latitude (parallel).

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Equinox

An equinox is commonly regarded as the moment the plane (extended indefinitely in all directions) of Earth's equator passes through the center of the Sun, which occurs twice each year, around 20 March and 22-23 September.

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Eratosthenes

Eratosthenes of Cyrene (Ἐρατοσθένης ὁ Κυρηναῖος,; –) was a Greek mathematician, geographer, poet, astronomer, and music theorist.

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Ernest Rutherford

Ernest Rutherford, 1st Baron Rutherford of Nelson, HFRSE LLD (30 August 1871 – 19 October 1937) was a New Zealand-born British physicist who came to be known as the father of nuclear physics.

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Escape velocity

In physics, escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a massive body.

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European Space Agency

The European Space Agency (ESA; Agence spatiale européenne, ASE; Europäische Weltraumorganisation) is an intergovernmental organisation of 22 member states dedicated to the exploration of space.

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Extinction event

An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth.

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Extreme ultraviolet

Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths from 124 nm down to 10 nm, and therefore (by the Planck–Einstein equation) having photons with energies from 10 eV up to 124 eV (corresponding to 124 nm to 10 nm respectively).

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Eye (journal)

Eye is a monthly peer-reviewed medical journal covering ophthalmology.

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Fall of the Western Roman Empire

The Fall of the Western Roman Empire (also called Fall of the Roman Empire or Fall of Rome) was the process of decline in the Western Roman Empire in which it failed to enforce its rule, and its vast territory was divided into several successor polities.

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Fixed stars

The fixed stars (stellae fixae) comprise the background of astronomical objects that appear to not move relative to each other in the night sky compared to the foreground of Solar System objects that do.

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Flattening

Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively.

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Flavour (particle physics)

In particle physics, flavour or flavor refers to the species of an elementary particle.

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Formation and evolution of the Solar System

The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud.

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Fourth Dynasty of Egypt

The Fourth Dynasty of ancient Egypt (notated Dynasty IV or Dynasty 4) is characterized as a "golden age" of the Old Kingdom of Egypt.

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Fractionation

Fractionation is a separation process in which a certain quantity of a mixture (gas, solid, liquid, enzymes, suspension, or isotope) is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient.

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Fraunhofer lines

In physics and optics, the Fraunhofer lines are a set of spectral lines named after the German physicist Joseph von Fraunhofer (1787–1826).

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Fred Hoyle

Sir Fred Hoyle FRS (24 June 1915 – 20 August 2001) was a British astronomer who formulated the theory of stellar nucleosynthesis.

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G-type main-sequence star

A G-type main-sequence star (Spectral type: G-V), often (and imprecisely) called a yellow dwarf, or G dwarf star, is a main-sequence star (luminosity class V) of spectral type G. Such a star has about 0.84 to 1.15 solar masses and surface temperature of between 5,300 and 6,000 K., G. M. H. J. Habets and J. R. W. Heintze, Astronomy and Astrophysics Supplement 46 (November 1981), pp.

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Galactic Center

The Galactic Center is the rotational center of the Milky Way.

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Galactic coordinate system

The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way galaxy, and the fundamental plane parallel to an approximation of the galactic plane but offset to its north.

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Galactic habitable zone

In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life might most likely develop.

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Galactic plane

The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies.

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Galactic year

The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy.

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Galileo Galilei

Galileo Galilei (15 February 1564Drake (1978, p. 1). The date of Galileo's birth is given according to the Julian calendar, which was then in force throughout Christendom. In 1582 it was replaced in Italy and several other Catholic countries with the Gregorian calendar. Unless otherwise indicated, dates in this article are given according to the Gregorian calendar. – 8 January 1642) was an Italian polymath.

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Gamma ray

A gamma ray or gamma radiation (symbol γ or \gamma), is penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei.

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Gas giant

A gas giant is a giant planet composed mainly of hydrogen and helium.

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Gaulish language

Gaulish was an ancient Celtic language that was spoken in parts of Europe as late as the Roman Empire.

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Geminga

Geminga is a neutron star approximately 250 parsecs (around 800 light years) from the Sun in the constellation Gemini.

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Genesis (spacecraft)

Genesis was a NASA sample-return probe that collected a sample of solar wind particles and returned them to Earth for analysis.

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Geoffrey Burbidge

Geoffrey Ronald Burbidge FRS (24 September 1925 – 26 January 2010) was an English astronomy professor and theoretical astrophysicist, most recently at the University of California, San Diego.

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Geophysical Research Letters

Geophysical Research Letters is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974.

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Germanic languages

The Germanic languages are a branch of the Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania, and Southern Africa.

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Giga-

Giga is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or 000).

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Giovanni Domenico Cassini

Giovanni Domenico Cassini (8 June 1625 – 14 September 1712) was an Italian (naturalised French) mathematician, astronomer and engineer.

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Goddard Institute for Space Studies

The Goddard Institute for Space Studies (GISS) is a laboratory in the Earth Sciences Division of NASA's Goddard Space Flight Center and a unit of the Columbia University Earth Institute.

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Goddard Space Flight Center

The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States.

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Gold

Gold is a chemical element with symbol Au (from aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally.

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Gothic language

Gothic is an extinct East Germanic language that was spoken by the Goths.

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Gould Belt

The Gould Belt is a partial ring of stars in the Milky Way, about 3000 light years across, tilted toward the galactic plane by about 16 to 20 degrees.

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Granule (solar physics)

Granules on the photosphere of the Sun are caused by convection currents (thermal columns, Bénard cells) of plasma within the Sun's convective zone.

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Gravitational collapse

Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity.

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Gravity

Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another.

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Green flash

Green flashes and green rays are optical phenomena that sometimes occur just after sunset or right before sunrise.

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Greenhouse gas

A greenhouse gas is a gas in an atmosphere that absorbs and emits radiant energy within the thermal infrared range.

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Halo (optical phenomenon)

Halo (from Greek ἅλως, halōs) is the name for a family of optical phenomena produced by sunlight interacting with ice crystals suspended in the atmosphere.

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Han dynasty

The Han dynasty was the second imperial dynasty of China (206 BC–220 AD), preceded by the Qin dynasty (221–206 BC) and succeeded by the Three Kingdoms period (220–280 AD). Spanning over four centuries, the Han period is considered a golden age in Chinese history. To this day, China's majority ethnic group refers to themselves as the "Han Chinese" and the Chinese script is referred to as "Han characters". It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han, and briefly interrupted by the Xin dynasty (9–23 AD) of the former regent Wang Mang. This interregnum separates the Han dynasty into two periods: the Western Han or Former Han (206 BC–9 AD) and the Eastern Han or Later Han (25–220 AD). The emperor was at the pinnacle of Han society. He presided over the Han government but shared power with both the nobility and appointed ministers who came largely from the scholarly gentry class. The Han Empire was divided into areas directly controlled by the central government using an innovation inherited from the Qin known as commanderies, and a number of semi-autonomous kingdoms. These kingdoms gradually lost all vestiges of their independence, particularly following the Rebellion of the Seven States. From the reign of Emperor Wu (r. 141–87 BC) onward, the Chinese court officially sponsored Confucianism in education and court politics, synthesized with the cosmology of later scholars such as Dong Zhongshu. This policy endured until the fall of the Qing dynasty in 1911 AD. The Han dynasty saw an age of economic prosperity and witnessed a significant growth of the money economy first established during the Zhou dynasty (c. 1050–256 BC). The coinage issued by the central government mint in 119 BC remained the standard coinage of China until the Tang dynasty (618–907 AD). The period saw a number of limited institutional innovations. To finance its military campaigns and the settlement of newly conquered frontier territories, the Han government nationalized the private salt and iron industries in 117 BC, but these government monopolies were repealed during the Eastern Han dynasty. Science and technology during the Han period saw significant advances, including the process of papermaking, the nautical steering ship rudder, the use of negative numbers in mathematics, the raised-relief map, the hydraulic-powered armillary sphere for astronomy, and a seismometer for measuring earthquakes employing an inverted pendulum. The Xiongnu, a nomadic steppe confederation, defeated the Han in 200 BC and forced the Han to submit as a de facto inferior partner, but continued their raids on the Han borders. Emperor Wu launched several military campaigns against them. The ultimate Han victory in these wars eventually forced the Xiongnu to accept vassal status as Han tributaries. These campaigns expanded Han sovereignty into the Tarim Basin of Central Asia, divided the Xiongnu into two separate confederations, and helped establish the vast trade network known as the Silk Road, which reached as far as the Mediterranean world. The territories north of Han's borders were quickly overrun by the nomadic Xianbei confederation. Emperor Wu also launched successful military expeditions in the south, annexing Nanyue in 111 BC and Dian in 109 BC, and in the Korean Peninsula where the Xuantu and Lelang Commanderies were established in 108 BC. After 92 AD, the palace eunuchs increasingly involved themselves in court politics, engaging in violent power struggles between the various consort clans of the empresses and empresses dowager, causing the Han's ultimate downfall. Imperial authority was also seriously challenged by large Daoist religious societies which instigated the Yellow Turban Rebellion and the Five Pecks of Rice Rebellion. Following the death of Emperor Ling (r. 168–189 AD), the palace eunuchs suffered wholesale massacre by military officers, allowing members of the aristocracy and military governors to become warlords and divide the empire. When Cao Pi, King of Wei, usurped the throne from Emperor Xian, the Han dynasty would eventually collapse and ceased to exist.

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Hans Bethe

Hans Albrecht Bethe (July 2, 1906 – March 6, 2005) was a German-American nuclear physicist who made important contributions to astrophysics, quantum electrodynamics and solid-state physics, and won the 1967 Nobel Prize in Physics for his work on the theory of stellar nucleosynthesis.

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HarperCollins

HarperCollins Publishers L.L.C. is one of the world's largest publishing companies and is one of the Big Five English-language publishing companies, alongside Hachette, Macmillan, Penguin Random House, and Simon & Schuster.

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Heat transfer

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems.

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Helen of Troy

In Greek mythology, Helen of Troy (Ἑλένη, Helénē), also known as Helen of Sparta, or simply Helen, was said to have been the most beautiful woman in the world, who was married to King Menelaus of Sparta, but was kidnapped by Prince Paris of Troy, resulting in the Trojan War when the Achaeans set out to reclaim her and bring her back to Sparta.

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Heliocentrism

Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System.

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Helios

Helios (Ἥλιος Hēlios; Latinized as Helius; Ἠέλιος in Homeric Greek) is the god and personification of the Sun in Greek mythology.

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Helios (spacecraft)

Helios-A and Helios-B (also known as and), are a pair of probes launched into heliocentric orbit for the purpose of studying solar processes.

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Heliosphere

The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto.

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Heliospheric current sheet

The heliospheric current sheet is the surface within the Solar System where the polarity of the Sun's magnetic field changes from north to south.

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Helium

Helium (from lit) is a chemical element with symbol He and atomic number 2.

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Helium flash

A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low mass stars (between 0.8 solar masses and 2.0) during their red giant phase (the Sun is predicted to experience a flash 1.2 billion years after it leaves the main sequence).

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Hercules (constellation)

Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles.

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Heresy

Heresy is any belief or theory that is strongly at variance with established beliefs or customs, in particular the accepted beliefs of a church or religious organization.

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Hermann von Helmholtz

Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist who made significant contributions in several scientific fields.

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Herschel wedge

A Herschel wedge or Herschel prism is an optical prism used in solar observation to refract most of the light out of the optical path, allowing safe visual observation.

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Hinduism

Hinduism is an Indian religion and dharma, or a way of life, widely practised in the Indian subcontinent.

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Horizon

The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not.

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Horizontal branch

The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red giant branch in stars whose masses are similar to the Sun's.

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Human sacrifice

Human sacrifice is the act of killing one or more humans, usually as an offering to a deity, as part of a ritual.

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Human skin color

Human skin color ranges in variety from the darkest brown to the lightest hues.

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Hydra (constellation)

Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees.

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Hydrogen

Hydrogen is a chemical element with symbol H and atomic number 1.

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Hydrogen anion

The hydrogen anion, H−, is a negative ion of hydrogen, that is, a hydrogen atom that has captured an extra electron.

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Hydrogen atom

A hydrogen atom is an atom of the chemical element hydrogen.

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Hydrostatic equilibrium

In fluid mechanics, a fluid is said to be in hydrostatic equilibrium or hydrostatic balance when it is at rest, or when the flow velocity at each point is constant over time.

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Hydrothermal vent

A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues.

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Hyperfine structure

In atomic physics, hyperfine structure refers to small shifts and splittings in the energy levels of atoms, molecules and ions, due to interaction between the state of the nucleus and the state of the electron clouds.

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Ibn Yunus

Abu al-Hasan 'Ali ibn 'Abd al-Rahman ibn Ahmad ibn Yunus al-Sadafi al-Misri (Arabic: ابن يونس; c. 950 – 1009) was an important Egyptian Muslim astronomer and mathematician, whose works are noted for being ahead of their time, having been based on meticulous calculations and attention to detail.

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Ice age

An ice age is a period of long-term reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers.

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Ice giant

An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur.

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Iconography

Iconography, as a branch of art history, studies the identification, description, and the interpretation of the content of images: the subjects depicted, the particular compositions and details used to do so, and other elements that are distinct from artistic style.

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Impact event

An impact event is a collision between astronomical objects causing measurable effects.

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Inanna

Inanna was the ancient Sumerian goddess of love, beauty, sex, desire, fertility, war, combat, justice, and political power.

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Inca Empire

The Inca Empire (Quechua: Tawantinsuyu, "The Four Regions"), also known as the Incan Empire and the Inka Empire, was the largest empire in pre-Columbian America, and possibly the largest empire in the world in the early 16th century.

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Indian Space Research Organisation

The Indian Space Research Organisation (ISRO) is the space agency of the Government of India headquartered in the city of Bangalore.

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Indo-European languages

The Indo-European languages are a language family of several hundred related languages and dialects.

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Infobase Publishing

Infobase Publishing is an American publisher of reference book titles and textbooks geared towards the North American library, secondary school, and university-level curriculum markets.

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Infrared

Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.

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International Journal of Astrobiology

The International Journal of Astrobiology (IJA) is a peer-reviewed scientific journal established in 2002 and published by Cambridge University Press that covers research on the prebiotic chemistry, origin, evolution, distribution, and future of life on Earth and beyond, SETI (Search for extraterrestrial intelligence), societal and educational aspects of astrobiology.

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Interplanetary magnetic field

The interplanetary magnetic field (IMF), now more commonly referred to as the heliospheric magnetic field (HMF), is the component of the solar magnetic field which is dragged out from the solar corona by the solar wind flow to fill the Solar System.

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Interpretatio graeca

Interpretatio graeca (Latin, "Greek translation" or "interpretation by means of Greek ") is a discourse in which ancient Greek religious concepts and practices, deities, and myths are used to interpret or attempt to understand the mythology and religion of other cultures.

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Interstellar medium

In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.

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Inverse-square law

The inverse-square law, in physics, is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

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Inversion (meteorology)

In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude.

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Ion

An ion is an atom or molecule that has a non-zero net electrical charge (its total number of electrons is not equal to its total number of protons).

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Ionization

Ionization or ionisation, is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes.

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Ionosphere

The ionosphere is the ionized part of Earth's upper atmosphere, from about to altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere.

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Iron

Iron is a chemical element with symbol Fe (from ferrum) and atomic number 26.

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Iron group

In chemistry and physics, the iron group refers to elements that are in some way related to iron.

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Isaac Newton

Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, astronomer, theologian, author and physicist (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time, and a key figure in the scientific revolution.

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Isis (journal)

Isis is a quarterly peer-reviewed academic journal published by the University of Chicago Press.

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Isotope

Isotopes are variants of a particular chemical element which differ in neutron number.

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Isotopes of iron

Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over 3.1×1022 years), 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe.

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JAXA

The is the Japanese national aerospace and space agency.

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Jean Richer

Jean Richer (1630–1696) was a French astronomer and assistant (élève astronome) at The French Academy of Sciences, under the direction of Giovanni Domenico Cassini.

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Jesus

Jesus, also referred to as Jesus of Nazareth and Jesus Christ, was a first-century Jewish preacher and religious leader.

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Jet Propulsion Laboratory

The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in Pasadena, California, United States, with large portions of the campus in La Cañada Flintridge, California.

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Joseph von Fraunhofer

Joseph Ritter von Fraunhofer (6 March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer.

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Journal of Atmospheric and Solar-Terrestrial Physics

The Journal of Atmospheric and Solar-Terrestrial Physics is a monthly peer-reviewed scientific journal covering the atmospheric and earth sciences.

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Journal of Geophysical Research

The Journal of Geophysical Research is a peer-reviewed scientific journal.

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Journal of Physics: Conference Series

Journal of Physics: Conference Series (JPCS) is a peer-reviewed, open-access publication from IOP Publishing providing readers with the latest developments in physics presented at international conferences.

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Journal of the British Astronomical Association

The Journal of the British Astronomical Association is a peer-reviewed scientific journal of astronomy published by the British Astronomical Association since October 1890.

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Julian year (astronomy)

In astronomy, a Julian year (symbol: a) is a unit of measurement of time defined as exactly 365.25 days of SI seconds each.

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Jupiter

Jupiter is the fifth planet from the Sun and the largest in the Solar System.

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Kelvin

The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics.

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Kelvin–Helmholtz mechanism

The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools.

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Kinetic energy

In physics, the kinetic energy of an object is the energy that it possesses due to its motion.

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Lagrangian point

In celestial mechanics, the Lagrangian points (also Lagrange points, L-points, or libration points) are positions in an orbital configuration of two large bodies, wherein a small object, affected only by the gravitational forces from the two larger objects, will maintain its position relative to them.

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Lapse rate

Lapse rate is the rate at which Earth's atmospheric temperature decreases with an increase in altitude, or increases with the decrease in altitude.

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Large Angle and Spectrometric Coronagraph

The Large Angle and Spectrometric Coronagraph (LASCO) is one of a number of instruments aboard the Solar and Heliospheric Observatory satellite (SOHO).

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Latitude

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface.

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Leo (constellation)

Leo is one of the constellations of the zodiac, lying between Cancer the crab to the west and Virgo the maiden to the east.

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Life

Life is a characteristic that distinguishes physical entities that do have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate.

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Light

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.

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Limb darkening

Limb darkening is an optical effect seen in stars (including the Sun), where the center part of the disk appears brighter than the edge or limb of the image.

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List of brightest stars

This is a list of the brightest naked eye stars to +2.50 magnitude, as determined by their maximum, total, or combined apparent visual magnitudes as seen from Earth.

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List of Emperors of Japan

This list of Emperors of Japan presents the traditional order of succession.

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List of nearest stars and brown dwarfs

The following two lists include all the known stars and brown dwarfs that are within of the Sun, or were/will be within in the astronomically near past or future.

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Lithuanian language

Lithuanian (lietuvių kalba) is a Baltic language spoken in the Baltic region.

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Little Ice Age

The Little Ice Age (LIA) was a period of cooling that occurred after the Medieval Warm Period.

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Local Bubble

The Local Bubble, or Local Cavity, is a relative cavity in the interstellar medium (ISM) in the Orion Arm of the Milky Way.

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Local Interstellar Cloud

The Local Interstellar Cloud (LIC), also known as the Local Fluff, is the interstellar cloud roughly across through which the Solar System is currently moving.

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Local standard of rest

In astronomy, the local standard of rest or LSR follows the mean motion of material in the Milky Way in the neighborhood of the Sun.

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Lumen (unit)

The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source.

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Luminance

Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction.

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Luminosity

In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.

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Luminous efficacy

Luminous efficacy is a measure of how well a light source produces visible light.

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Macmillan Publishers

Macmillan Publishers Ltd (occasionally known as the Macmillan Group) is an international publishing company owned by Holtzbrinck Publishing Group.

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Macmillan's Magazine

Macmillan's Magazine was a monthly British magazine from 1859 to 1907 published by Alexander Macmillan.

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Magnesium

Magnesium is a chemical element with symbol Mg and atomic number 12.

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Magnetic field

A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.

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Magnetic reconnection

Magnetic reconnection is a physical process in highly conducting plasmas in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration.

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Magnetohydrodynamics

Magnetohydrodynamics (MHD; also magneto-fluid dynamics or hydro­magnetics) is the study of the magnetic properties of electrically conducting fluids.

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Main sequence

In astronomy, the main sequence is a continuous and distinctive band of stars that appear on plots of stellar color versus brightness.

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Manganese

Manganese is a chemical element with symbol Mn and atomic number 25.

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Margaret Burbidge

Eleanor Margaret Burbidge (née Peachey), FRS (born August 12, 1919 in Davenport) is a British-born American astrophysicist, noted for original research and holding many administrative posts, including Director of the Royal Greenwich Observatory.

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Mars

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.

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Marshall Space Flight Center

The George C. Marshall Space Flight Center (MSFC), located in Huntsville, Alabama, is the U.S. government's civilian rocketry and spacecraft propulsion research center.

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Mass

Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.

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Mass–energy equivalence

In physics, mass–energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula: E.

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Mathematical model

A mathematical model is a description of a system using mathematical concepts and language.

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Maunder Minimum

The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period around 1645 to 1715 during which sunspots became exceedingly rare, as was then noted by solar observers.

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Megalith

A megalith is a large stone that has been used to construct a structure or monument, either alone or together with other stones.

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Meghnad Saha

Meghnad Saha FRS (6 October 1893 – 16 February 1956) was an Indian astrophysicist best known for his development of the Saha ionization equation, used to describe chemical and physical conditions in stars.

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Mercury (planet)

Mercury is the smallest and innermost planet in the Solar System.

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Merriam-Webster

Merriam–Webster, Incorporated is an American company that publishes reference books which is especially known for its dictionaries.

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Messiah

In Abrahamic religions, the messiah or messias is a saviour or liberator of a group of people.

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Metabolism

Metabolism (from μεταβολή metabolē, "change") is the set of life-sustaining chemical transformations within the cells of organisms.

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Metallicity

In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.

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Meteorite

A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon.

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Meteoritics & Planetary Science

Meteoritics & Planetary Science is a monthly peer-reviewed scientific journal that was established in 1953.

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Methane

Methane is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen).

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Mexico

Mexico (México; Mēxihco), officially called the United Mexican States (Estados Unidos Mexicanos) is a federal republic in the southern portion of North America.

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Middle Dutch

Middle Dutch is a collective name for a number of closely related West Germanic dialects (whose ancestor was Old Dutch) spoken and written between 1150 and 1500.

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Mie scattering

The Mie solution to Maxwell's equations (also known as the Lorenz–Mie solution, the Lorenz–Mie–Debye solution or Mie scattering) describes the scattering of an electromagnetic plane wave by a homogeneous sphere.

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Milankovitch cycles

Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years.

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Milky Way

The Milky Way is the galaxy that contains our Solar System.

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Minute and second of arc

A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to of one degree.

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Mnajdra

Mnajdra (L-Imnajdra) is a megalithic temple complex found on the southern coast of the Mediterranean island of Malta.

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Molecular cloud

A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H2).

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Moment of inertia factor

In planetary sciences, the moment of inertia factor or normalized polar moment of inertia is a dimensionless quantity that characterizes the radial distribution of mass inside a planet or satellite.

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Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.

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Moon

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.

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Myriad

A myriad (from Ancient Greek label) is technically the number ten thousand; in that sense, the term is used almost exclusively in translations from Greek, Latin, or Chinese, or when talking about ancient Greek numbers.

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Nabta Playa

Nabta Playa was once a large internally drained basin in the Nubian Desert, located approximately 800 kilometers south of modern-day Cairo or about 100 kilometers west of Abu Simbel in southern Egypt, 22.51° north, 30.73° east.

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Naked eye

Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical instrument, such as a telescope or microscope.

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Names of the days of the week

The names of the days of the week in many languages are derived from the names of the classical planets in Hellenistic astrology, which were in turn named after contemporary deities, a system introduced by the Roman Empire during Late Antiquity.

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Nanoflares

A nanoflare is a very small episodic heating event which happens in the corona, the external atmosphere of the Sun.

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NASA

The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.

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Nature (journal)

Nature is a British multidisciplinary scientific journal, first published on 4 November 1869.

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Neon

Neon is a chemical element with symbol Ne and atomic number 10.

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Neptune

Neptune is the eighth and farthest known planet from the Sun in the Solar System.

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Neutrino

A neutrino (denoted by the Greek letter ν) is a fermion (an elementary particle with half-integer spin) that interacts only via the weak subatomic force and gravity.

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Neutrino oscillation

Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon, or tau) can later be measured to have a different flavor.

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Neutron capture

Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus.

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New Kingdom of Egypt

The New Kingdom, also referred to as the Egyptian Empire, is the period in ancient Egyptian history between the 16th century BC and the 11th century BC, covering the 18th, 19th, and 20th dynasties of Egypt.

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New Scientist

New Scientist, first published on 22 November 1956, is a weekly, English-language magazine that covers all aspects of science and technology.

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Newgrange

Newgrange (Sí an Bhrú or Brú na Bóinne) is a prehistoric monument in County Meath, Ireland, located west of Drogheda on the north side of the River Boyne.

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Nicolaus Copernicus

Nicolaus Copernicus (Mikołaj Kopernik; Nikolaus Kopernikus; Niklas Koppernigk; 19 February 1473 – 24 May 1543) was a Renaissance-era mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe, likely independently of Aristarchus of Samos, who had formulated such a model some eighteen centuries earlier.

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Nitrogen

Nitrogen is a chemical element with symbol N and atomic number 7.

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Noble gas

The noble gases (historically also the inert gases) make up a group of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity.

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Norman Lockyer

Sir Joseph Norman Lockyer, KCB FRS (17 May 1836 – 16 August 1920), known simply as Norman Lockyer, was an English scientist and astronomer.

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Nuclear fusion

In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons).

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Nuclear Instruments and Methods in Physics Research

Nuclear Instruments and Methods in Physics Research (Nucl. Instrum. Methods Phys. Res.) is a peer-reviewed scientific journal published by Elsevier.

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Nuclear transmutation

Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element.

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Nucleocosmochronology

Nucleocosmochronology or nuclear cosmochronology is a technique used to determine timescales for astrophysical objects and events.

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Nucleosynthesis

Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.

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Observatory

An observatory is a location used for observing terrestrial or celestial events.

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Old English

Old English (Ænglisc, Anglisc, Englisc), or Anglo-Saxon, is the earliest historical form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages.

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Old Frisian

Old Frisian is a West Germanic language spoken between the 8th and 16th centuries in the area between the Rhine and Weser on the European North Sea coast.

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Old High German

Old High German (OHG, Althochdeutsch, German abbr. Ahd.) is the earliest stage of the German language, conventionally covering the period from around 700 to 1050.

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Old Norse

Old Norse was a North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements from about the 9th to the 13th century.

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Old Saxon

Old Saxon, also known as Old Low German, was a Germanic language and the earliest recorded form of Low German (spoken nowadays in Northern Germany, the northeastern Netherlands, southern Denmark, the Americas and parts of Eastern Europe).

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Oort constants

The Oort constants (discovered by Jan Oort) A and B are empirically derived parameters that characterize the local rotational properties of our galaxy, the Milky Way, in the following manner: \begin & A.

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Opacity (optics)

Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light.

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Optical phenomena

Optical phenomena are any observable events that result from the interaction of light and matter.

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Optics

Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it.

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Optics and Photonics News

Optics & Photonics News is the membership magazine of The Optical Society.

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Orbit

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet.

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Orbital speed

In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if the object is much less massive than the largest body in the system, its speed relative to that largest body.

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Orion Arm

The Orion Arm is a minor spiral arm of the Milky Way some across and approximately in length, containing the Solar System, including the Earth.

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Oscillator strength

In spectroscopy, oscillator strength is a dimensionless quantity that expresses the probability of absorption or emission of electromagnetic radiation in transitions between energy levels of an atom or molecule.

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Outer space

Outer space, or just space, is the expanse that exists beyond the Earth and between celestial bodies.

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Oxygen

Oxygen is a chemical element with symbol O and atomic number 8.

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Ozone layer

The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation.

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Parsec

The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.

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Peloponnese

The Peloponnese or Peloponnesus (Πελοπόννησος, Peloponnisos) is a peninsula and geographic region in southern Greece.

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Pericles

Pericles (Περικλῆς Periklēs, in Classical Attic; c. 495 – 429 BC) was a prominent and influential Greek statesman, orator and general of Athens during the Golden Age — specifically the time between the Persian and Peloponnesian wars.

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Perihelion and aphelion

The perihelion of any orbit of a celestial body about the Sun is the point where the body comes nearest to the Sun.

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Perseus Arm

The Perseus Arm is one of two major spiral arms of the Milky Way galaxy.

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Perturbation (astronomy)

In astronomy, perturbation is the complex motion of a massive body subject to forces other than the gravitational attraction of a single other massive body.

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Pharaoh

Pharaoh (ⲡⲣ̅ⲣⲟ Prro) is the common title of the monarchs of ancient Egypt from the First Dynasty (c. 3150 BCE) until the annexation of Egypt by the Roman Empire in 30 BCE, although the actual term "Pharaoh" was not used contemporaneously for a ruler until circa 1200 BCE.

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Philosopher

A philosopher is someone who practices philosophy, which involves rational inquiry into areas that are outside either theology or science.

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Phosphene

A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye.

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Photon

The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles).

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Photosphere

The photosphere is a star's outer shell from which light is radiated.

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Photosynthesis

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation).

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Phys.org

Phys.org is a science, research and technology news aggregator where much of the content is republished directly from press releases and news agencies-in a practice known as churnalism.

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Physical Review

Physical Review is an American peer-reviewed scientific journal established in 1893 by Edward Nichols.

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Physics Reports

Physics Reports is a peer-reviewed scientific journal, a review section of Physics Letters that has been published by Elsevier since 1971.

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Pioneer 6, 7, 8, and 9

Pioneer 6, 7, 8, and 9 were space probes in the Pioneer program.

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Pioneer program

The Pioneer program is a series of United States unmanned space missions that were designed for planetary exploration.

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Planetary nebula

A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.

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Plasma (physics)

Plasma (Henry George Liddell, Robert Scott, A Greek English Lexicon, on Perseus) is one of the four fundamental states of matter, and was first described by chemist Irving Langmuir in the 1920s.

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PLOS Biology

PLOS Biology is a peer-reviewed scientific journal covering all aspects of Biology.

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Poles of astronomical bodies

The poles of astronomical bodies are determined based on their axis of rotation in relation to the celestial poles of the celestial sphere.

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Prehistory

Human prehistory is the period between the use of the first stone tools 3.3 million years ago by hominins and the invention of writing systems.

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Princeton University Press

Princeton University Press is an independent publisher with close connections to Princeton University.

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Prism

In optics, a prism is a transparent optical element with flat, polished surfaces that refract light.

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Proto-Germanic language

Proto-Germanic (abbreviated PGmc; German: Urgermanisch; also called Common Germanic, German: Gemeingermanisch) is the reconstructed proto-language of the Germanic branch of the Indo-European languages.

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Proto-Indo-European religion

Proto-Indo-European religion is the belief system adhered to by the Proto-Indo-Europeans.

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Proton

| magnetic_moment.

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Proton–proton chain reaction

The proton–proton chain reaction is one of the two (known) sets of fusion reactions by which stars convert hydrogen to helium.

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Protostar

A protostar is a very young star that is still gathering mass from its parent molecular cloud.

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Proxima Centauri

Proxima Centauri, or Alpha Centauri C, is a red dwarf, a small low-mass star, about from the Sun in the constellation of Centaurus.

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Ptolemy

Claudius Ptolemy (Κλαύδιος Πτολεμαῖος, Klaúdios Ptolemaîos; Claudius Ptolemaeus) was a Greco-Roman mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.

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Pupil

The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.

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Pyramid

A pyramid (from πυραμίς) is a structure whose outer surfaces are triangular and converge to a single point at the top, making the shape roughly a pyramid in the geometric sense.

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Queen of heaven (antiquity)

Queen of Heaven was a title given to a number of ancient sky goddesses worshipped throughout the ancient Mediterranean and Near East during ancient times.

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Ra

Ra (rꜥ or rˤ; also transliterated rˤw; cuneiform: ri-a or ri-ia) or Re (ⲣⲏ, Rē) is the ancient Egyptian sun god.

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Radiance

In radiometry, radiance is the radiant flux emitted, reflected, transmitted or received by a given surface, per unit solid angle per unit projected area.

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Radiation

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.

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Radioactive decay

Radioactive decay (also known as nuclear decay or radioactivity) is the process by which an unstable atomic nucleus loses energy (in terms of mass in its rest frame) by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino in the case of electron capture, gamma ray, or electron in the case of internal conversion.

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Radiometric dating

Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.

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Radius

In classical geometry, a radius of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length.

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Rayleigh scattering

Rayleigh scattering (pronounced), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.

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Rayleigh–Bénard convection

Rayleigh–Bénard convection is a type of natural convection, occurring in a plane horizontal layer of fluid heated from below, in which the fluid develops a regular pattern of convection cells known as Bénard cells.

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Red clump

The red clump is a clustering of red giants in the Hertzsprung–Russell diagram at around 5,000 K and absolute magnitude (MV) +0.5, slightly hotter than most red-giant-branch stars of the same luminosity.

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Red dwarf

A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.

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Red giant

A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses) in a late phase of stellar evolution.

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Red-giant branch

The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution.

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Refraction

Refraction is the change in direction of wave propagation due to a change in its transmission medium.

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Reptile

Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives.

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Reviews of Modern Physics

Reviews of Modern Physics is a quarterly peer-reviewed scientific journal published by the American Physical Society.

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Revista Mexicana de Astronomía y Astrofísica

The Revista Mexicana de Astronomía y Astrofísica (often RevMexAA or RMxAA) is a peer-reviewed scientific journal of astronomy founded in 1974.

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Right ascension

Right ascension (abbreviated RA; symbol) is the angular distance measured only eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point above the earth in question.

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Roman Empire

The Roman Empire (Imperium Rōmānum,; Koine and Medieval Greek: Βασιλεία τῶν Ῥωμαίων, tr.) was the post-Roman Republic period of the ancient Roman civilization, characterized by government headed by emperors and large territorial holdings around the Mediterranean Sea in Europe, Africa and Asia.

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Rotation

A rotation is a circular movement of an object around a center (or point) of rotation.

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Sabbath

Sabbath is a day set aside for rest and worship.

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Sanskrit

Sanskrit is the primary liturgical language of Hinduism; a philosophical language of Hinduism, Sikhism, Buddhism and Jainism; and a former literary language and lingua franca for the educated of ancient and medieval India.

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Saturn

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.

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Saulė

Saulė (Saulė, Saule) is a solar goddess, the common Baltic solar deity in the Lithuanian and Latvian mythologies.

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Saw

A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge.

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Sól (sun)

Sól (Old Norse "Sun")Orchard (1997:152).

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Scholarpedia

Scholarpedia is an English-language online wiki-based encyclopedia with features commonly associated with open-access online academic journals, which aims to have quality content.

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Science (journal)

Science, also widely referred to as Science Magazine, is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals.

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Seleucus of Seleucia

Seleucus of Seleucia (Σέλευκος Seleukos; born c. 190 BC; fl. c. 150 BC) was a Hellenistic astronomer and philosopher.

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Shear stress

A shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section.

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Shinto

or kami-no-michi (among other names) is the traditional religion of Japan that focuses on ritual practices to be carried out diligently to establish a connection between present-day Japan and its ancient past.

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Shock wave

In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance.

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Silicon

Silicon is a chemical element with symbol Si and atomic number 14.

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Simon & Schuster

Simon & Schuster, Inc., a subsidiary of CBS Corporation, is an American publishing company founded in New York City in 1924 by Richard Simon and Max Schuster.

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Sirius

Sirius (a romanization of Greek Σείριος, Seirios,."glowing" or "scorching") is a star system and the brightest star in the Earth's night sky.

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Sky

The sky (or celestial dome) is everything that lies above the surface of the Earth, including the atmosphere and outer space.

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Skylab

Skylab was the United States' space station that orbited the Earth from 1973 to 1979, when it fell back to Earth amid huge worldwide media attention.

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Slavic languages

The Slavic languages (also called Slavonic languages) are the Indo-European languages spoken by the Slavic peoples.

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Society for Mathematical Biology

The Society for Mathematical Biology (SMB) is an international association co-founded in 1972 in USA by Drs.

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Sol Invictus

Sol Invictus ("Unconquered Sun") is the official sun god of the later Roman Empire and a patron of soldiers.

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Solar and Heliospheric Observatory

The Solar and Heliospheric Observatory (SOHO) is a spacecraft built by a European industrial consortium led by Matra Marconi Space (now Astrium) that was launched on a Lockheed Martin Atlas II AS launch vehicle on December 2, 1995, to study the Sun, and has discovered over 3000 comets.

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Solar apex

The solar apex, or the Apex of the Sun's Way, refers to the direction that the Sun travels with respect to the Local Standard of Rest.

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Solar calendar

A solar calendar is a calendar whose dates indicate the season or almost equivalently the position of the apparent position of the sun in relative to the stars.

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Solar constant

The solar constant is a flux density measuring mean solar electromagnetic radiation (solar irradiance) per unit area.

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Solar core

The core of the Sun is considered to extend from the center to about 0.2 to 0.25 of solar radius.

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Solar cycle

The solar cycle or solar magnetic activity cycle is the nearly periodic 11-year change in the Sun's activity (including changes in the levels of solar radiation and ejection of solar material) and appearance (changes in the number and size of sunspots, flares, and other manifestations).

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Solar deity

A solar deity (also sun god or sun goddess) is a sky deity who represents the Sun, or an aspect of it, usually by its perceived power and strength.

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Solar Dynamics Observatory

The Solar Dynamics Observatory (SDO) is a NASA mission which has been observing the Sun since 2010.

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Solar dynamo

The solar dynamo is the physical process that generates the Sun's magnetic field.

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Solar eclipse

A solar eclipse (as seen from the planet Earth) is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and when the Moon fully or partially blocks ("occults") the Sun.

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Solar energy

Solar energy is radiant light and heat from the Sun that is harnessed using a range of ever-evolving technologies such as solar heating, photovoltaics, solar thermal energy, solar architecture, molten salt power plants and artificial photosynthesis.

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Solar flare

A solar flare is a sudden flash of increased Sun's brightness, usually observed near its surface.

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Solar irradiance

Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.

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Solar mass

The solar mass is a standard unit of mass in astronomy, equal to approximately.

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Solar maximum

Solar maximum or solar max is a regular period of greatest Sun activity during the 11-year solar cycle.

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Solar Maximum Mission

The Solar Maximum Mission satellite (or SolarMax) was designed to investigate Solar phenomena, particularly solar flares.

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Solar minimum

Solar minimum is the period of least solar activity in the 11 year solar cycle of the sun.

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Solar neutrino problem

The solar neutrino problem concerned a large discrepancy between the flux of solar neutrinos as predicted from the Sun's luminosity and measured directly.

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Solar Physics (journal)

Solar Physics is a peer-reviewed scientific journal published approximately monthly by Springer Science+Business Media.

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Solar prominence

A prominence is a large, bright, gaseous feature extending outward from the Sun's surface, often in a loop shape.

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Solar radius

Solar radius is a unit of distance used to express the size of stars in astronomy.

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Solar rotation

Solar rotation varies with latitude because the Sun is composed of a gaseous plasma.

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Solar System

The Solar SystemCapitalization of the name varies.

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Solar time

Solar time is a calculation of the passage of time based on the position of the Sun in the sky.

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Solar transition region

The solar transition region is a region of the Sun's atmosphere, between the chromosphere and corona.

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Solar wind

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona.

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Solstice

A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere.

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Space Science Reviews

Space Science Reviews is a peer reviewed, scientific journal of space science.

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Space Shuttle Challenger

Space Shuttle Challenger (Orbiter Vehicle Designation: OV-099) was the second orbiter of NASA's space shuttle program to be put into service, after ''Columbia''.

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Space weather

Space weather is a branch of space physics and aeronomy concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the magnetosphere, ionosphere, thermosphere, and exosphere.

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Space.com

Space.com is a space and astronomy news website.

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Spörer's law

Spörer's law predicts the variation of sunspot latitudes during a solar cycle.

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Spectral line

A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies.

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Spectroscopy

Spectroscopy is the study of the interaction between matter and electromagnetic radiation.

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Speed of light

The speed of light in vacuum, commonly denoted, is a universal physical constant important in many areas of physics.

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Spicule (solar physics)

In solar physics, a spicule is a dynamic jet of about 500 km diameter in the chromosphere of the Sun.

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Springer Science+Business Media

Springer Science+Business Media or Springer, part of Springer Nature since 2015, is a global publishing company that publishes books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing.

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Stadion (unit)

The stadion (στάδιον; stadium), formerly also anglicized as stade, was an ancient Greek unit of length, based on the length of a typical sports stadium of the time.

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Stanford University

Stanford University (officially Leland Stanford Junior University, colloquially the Farm) is a private research university in Stanford, California.

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Star

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.

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Star formation

Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars.

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Stellar classification

In astronomy, stellar classification is the classification of stars based on their spectral characteristics.

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Stellar evolution

Stellar evolution is the process by which a star changes over the course of time.

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Stellar nucleosynthesis

Stellar nucleosynthesis is the theory explaining the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions between atoms within the stars.

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Stellar population

During 1944, Walter Baade categorized groups of stars within the Milky Way into bluer stars associated with the spiral arms and the general position of yellow stars near the central galactic bulge or within globular star clusters.

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STEREO

STEREO (Solar Terrestrial Relations Observatory) is a solar observation mission.

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Stereoscopy

Stereoscopy (also called stereoscopics, or stereo imaging) is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision.

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Stonehenge

Stonehenge is a prehistoric monument in Wiltshire, England, west of Amesbury.

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STS-41-C

STS-41-C was NASA's 11th Space Shuttle mission, and the fifth mission of Space Shuttle ''Challenger''.

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Subgiant

A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as true giant stars.

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Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar FRS (19 October 1910 – 21 August 1995) was an Indian American astrophysicist who spent his professional life in the United States.

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Sulfur

Sulfur or sulphur is a chemical element with symbol S and atomic number 16.

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Sulis

In localised Celtic polytheism practised in Britain, Sulis was a deity worshipped at the thermal spring of Bath (now in Somerset).

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Sumer

SumerThe name is from Akkadian Šumeru; Sumerian en-ĝir15, approximately "land of the civilized kings" or "native land".

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Sun

The Sun is the star at the center of the Solar System.

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Sun dog

A sun dog (or sundog) or mock sun, formally called a parhelion (plural parhelia) in meteorology, is an atmospheric optical phenomenon that consists of a bright spot to the left or right of the Sun.

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Sun path

Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun.

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Sun tanning

Sun tanning or simply tanning is the process whereby skin color is darkened or tanned.

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Sun-Earth Day

Sun-Earth Day is a joint educational program established in 2000 by NASA and ESA.

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Sunburn

Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, commonly from the sun.

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Sunday

Sunday is the day of the week between Saturday and Monday.

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Sungazing

Sungazing is the act of looking directly into the sun.

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Sungrazing comet

A sungrazing comet is a comet that passes extremely close to the Sun at perihelion – sometimes within a few thousand kilometres of the Sun's surface.

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Sunlight

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

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Sunrise

Sunrise or sun up is the instant at which the upper edge of the Sun appears over the horizon in the morning.

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Sunset

Sunset or sundown is the daily disappearance of the Sun below the horizon as a result of Earth's rotation.

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Sunspot

Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas.

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Supergranulation

Supergranulation is a particular pattern of convection cells on the Sun's surface called supergranules.

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Supernatural

The supernatural (Medieval Latin: supernātūrālis: supra "above" + naturalis "natural", first used: 1520–1530 AD) is that which exists (or is claimed to exist), yet cannot be explained by laws of nature.

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Supernova

A supernova (plural: supernovae or supernovas, abbreviations: SN and SNe) is a transient astronomical event that occurs during the last stellar evolutionary stages of a star's life, either a massive star or a white dwarf, whose destruction is marked by one final, titanic explosion.

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Surface area

The surface area of a solid object is a measure of the total area that the surface of the object occupies.

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Surface brightness

In astronomy, surface brightness quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background.

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Surface gravity

The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface.

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Surya

Surya (सूर्य, IAST: ‘'Sūrya’') is a Sanskrit word that means the Sun.

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Syncretism

Syncretism is the combining of different beliefs, while blending practices of various schools of thought.

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Synodic day

A synodic day is the period it takes for a planet to rotate once in relation to the body it is orbiting.

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Tachocline

The tachocline is the transition region of the Sun between the radiative interior and the differentially rotating outer convective zone.

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Telescope

A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).

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Temperature gradient

A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location.

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Terrestrial planet

A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals.

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Tesla (unit)

The tesla (symbol T) is a derived unit of magnetic flux density (informally, magnetic field strength) in the International System of Units.

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Thames & Hudson

Thames & Hudson (also Thames and Hudson and sometimes T&H for brevity) is a publisher of illustrated books on art, architecture, design, and visual culture.

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The Astrophysical Journal

The Astrophysical Journal, often abbreviated ApJ (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler.

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The Boston Globe

The Boston Globe (sometimes abbreviated as The Globe) is an American daily newspaper founded and based in Boston, Massachusetts, since its creation by Charles H. Taylor in 1872.

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The Guardian

The Guardian is a British daily newspaper.

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The Sun in culture

The Sun, as the source of energy and light for life on earth has been a central object in culture and religion since prehistory.

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The Times Group

The Times Group is India’s largest media conglomerate, according to Financial Times as of March 2015.

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The Times of India

The Times of India (TOI) is an Indian English-language daily newspaper owned by The Times Group.

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Theory

A theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking.

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Thermal

A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft.

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Thermal conduction

Thermal conduction is the transfer of heat (internal energy) by microscopic collisions of particles and movement of electrons within a body.

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Thermal energy

Thermal energy is a term used loosely as a synonym for more rigorously-defined thermodynamic quantities such as the internal energy of a system; heat or sensible heat, which are defined as types of transfer of energy (as is work); or for the characteristic energy of a degree of freedom in a thermal system kT, where T is temperature and k is the Boltzmann constant.

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Thermal expansion

Thermal expansion is the tendency of matter to change in shape, area, and volume in response to a change in temperature.

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Thermal radiation

Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter.

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Thomas Harriot

Thomas Harriot (Oxford, c. 1560 – London, 2 July 1621), also spelled Harriott, Hariot or Heriot, was an English astronomer, mathematician, ethnographer and translator who made advances within the scientific field.

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Tidal force

The tidal force is an apparent force that stretches a body towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for the diverse phenomena, including tides, tidal locking, breaking apart of celestial bodies and formation of ring systems within Roche limit, and in extreme cases, spaghettification of objects.

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Timeline of the far future

While predictions of the future can never be absolutely certain, present understanding in various scientific fields allows for the prediction of far-future events, if only in the broadest outline.

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TNT

Trinitrotoluene (TNT), or more specifically 2,4,6-trinitrotoluene, is a chemical compound with the formula C6H2(NO2)3CH3.

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TNT equivalent

TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion.

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Tonatiuh

In Aztec mythology, Tonatiuh (Nahuatl: Ōllin Tōnatiuh "Movement of the Sun") was the sun god.

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Tonne

The tonne (Non-SI unit, symbol: t), commonly referred to as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000 kilograms;.

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Toroidal and poloidal

The earliest use of these terms cited by the Oxford English Dictionary (OED) is by Walter M. Elsasser (1946) in the context of the generation of the Earth's magnetic field by currents in the core, with "toroidal" being parallel to lines of latitude and "poloidal" being in the direction of the magnetic field (i.e. towards the poles).

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Transit of Venus

A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk.

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Triple-alpha process

The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon.

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Ultraviolet

Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.

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Ulysses (spacecraft)

Ulysses is a decommissioned robotic space probe whose primary mission was to orbit the Sun and study it at all latitudes.

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United States Naval Observatory

The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation and Timing (PNT) for the United States Navy and the United States Department of Defense.

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United States Naval Research Laboratory

The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps.

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University of Chicago Press

The University of Chicago Press is the largest and one of the oldest university presses in the United States.

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University of St Andrews

The University of St Andrews (informally known as St Andrews University or simply St Andrews; abbreviated as St And, from the Latin Sancti Andreae, in post-nominals) is a British public research university in St Andrews, Fife, Scotland.

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Uranium

Uranium is a chemical element with symbol U and atomic number 92.

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Uranus

Uranus is the seventh planet from the Sun.

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Utu

Utu later worshipped by East Semitic peoples as Shamash, was the ancient Mesopotamian god of the sun, justice, morality, and truth, and the twin brother of the goddess Inanna, the Queen of Heaven.

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Vega

Vega, also designated Alpha Lyrae (α Lyrae, abbreviated Alpha Lyr or α Lyr), is the brightest star in the constellation of Lyra, the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus.

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Velocity

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time.

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Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.

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Visible spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.

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Vitamin D

Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects.

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Volume

Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains.

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Voyager 1

Voyager 1 is a space probe launched by NASA on September 5, 1977.

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Watt

The watt (symbol: W) is a unit of power.

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Wave

In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport.

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White dwarf

A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter.

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William Alfred Fowler

William Alfred "Willy" Fowler (August 9, 1911 – March 14, 1995) was an American nuclear physicist, later astrophysicist, who, with Subrahmanyan Chandrasekhar won the 1983 Nobel Prize in Physics.

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William Herschel

Frederick William Herschel, (Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer, composer and brother of fellow astronomer Caroline Herschel, with whom he worked.

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William Thomson, 1st Baron Kelvin

William Thomson, 1st Baron Kelvin, (26 June 1824 – 17 December 1907) was a Scots-Irish mathematical physicist and engineer who was born in Belfast in 1824.

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Winter solstice

The winter solstice (or hibernal solstice), also known as midwinter, is an astronomical phenomenon marking the day with the shortest period of daylight and the longest night of the year.

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X-ray

X-rays make up X-radiation, a form of electromagnetic radiation.

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Xenon

Xenon is a chemical element with symbol Xe and atomic number 54.

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Yohkoh

Yohkoh (ようこう, Sunbeam in Japanese), known before launch as Solar-A, was a Solar observatory spacecraft of the Institute of Space and Astronautical Science (Japan), in collaboration with space agencies in the United States and the United Kingdom. It was launched into Earth orbit on August 30, 1991 by the M-3S-5 rocket from Kagoshima Space Center. It took its first soft X-ray image on September 13, 1991 21:53:40, and movie representations of the X-ray corona over 1991-2001 are available at the.

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Yotta-

Yotta is the largest decimal unit prefix in the metric system, denoting a factor of 1024 or; that is, one million million million million, or one septillion.

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Zenith

The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere.

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Zodiac

The zodiac is an area of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year.

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1,000,000,000

1,000,000,000 (one billion, short scale; one thousand million or milliard, yard, long scale) is the natural number following 999,999,999 and preceding 1,000,000,001.

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Atmosphere of the Sun, Closest star, Earth's sun, End of the Sun, Exploration of the Sun, Heliology, Internal structure of the Sun, Layers of the Sun, Local Star, Local star, Orbit of the Sun, Orbit of the sun, Parts of the sun, Sol (star), Solar X-ray astronomy, Solar astronomy, Solar atmosphere, Solar diameter, Solar glare, Solar magnetic field, Solar photosphere, Solarian, Star Sol, Structure of the Sun, Sun (astronomy), Sun (song), Sun (star), Sun characteristics, Sun gravity, Sun's atmosphere, Sun's orbit, The sun, Watch sun directly, 🌞.

References

[1] https://en.wikipedia.org/wiki/Sun

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