399 relations: Abd al-Rahman al-Sufi, Absolute magnitude, Achernar, Age of the universe, Al-Andalus, Al-Biruni, Albert A. 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'Abd al-Rahman al-Sufi (عبدالرحمن صوفی (December 7, 903 in Rey, Iran – May 25, 986 in Shiraz, Iran) was a Persian astronomer also known as 'Abd ar-Rahman as-Sufi, 'Abd al-Rahman Abu al-Husayn, 'Abdul Rahman Sufi, or 'Abdurrahman Sufi and, historically, in the West as Azophi and Azophi Arabus. The lunar crater Azophi and the minor planet 12621 Alsufi are named after him. Al-Sufi published his famous Book of Fixed Stars in 964, describing much of his work, both in textual descriptions and pictures. Al-Biruni reports that his work on the ecliptic was carried out in Shiraz. He lived at the Buyid court in Isfahan.
Absolute magnitude is a measure of the luminosity of a celestial object, on a logarithmic astronomical magnitude scale.
Achernar is the name of the primary (or 'A') component of the binary system designated Alpha Eridani (α Eridani, abbreviated Alf Eri, α Eri), which is the brightest 'star' or point of light in, and lying at the southern tip of, the constellation of Eridanus, and the tenth-brightest in the night sky.
In physical cosmology, the age of the universe is the time elapsed since the Big Bang.
Al-Andalus (الأنْدَلُس, trans.; al-Ándalus; al-Ândalus; al-Àndalus; Berber: Andalus), also known as Muslim Spain, Muslim Iberia, or Islamic Iberia, was a medieval Muslim territory and cultural domain occupying at its peak most of what are today Spain and Portugal.
Abū Rayḥān Muḥammad ibn Aḥmad Al-Bīrūnī (Chorasmian/ابوریحان بیرونی Abū Rayḥān Bērōnī; New Persian: Abū Rayḥān Bīrūnī) (973–1050), known as Al-Biruni (البيروني) in English, was an IranianD.J. Boilot, "Al-Biruni (Beruni), Abu'l Rayhan Muhammad b. Ahmad", in Encyclopaedia of Islam (Leiden), New Ed., vol.1:1236–1238.
Albert Abraham Michelson FFRS HFRSE (December 19, 1852 – May 9, 1931) was an American physicist known for his work on measuring the speed of light and especially for the Michelson–Morley experiment.
Algol, designated Beta Persei (β Persei, abbreviated Beta Per, β Per), known colloquially as the Demon Star, is a bright multiple star in the constellation of Perseus and one of the first non-nova variable stars to be discovered.
Abu'l Hassan Ali ibn Ridwan Al-Misri, أبو الحسن علي بن رضوان المصري (c. 988 - c. 1061) was an Arab of Egyptian origin who was a physician, astrologer and astronomer, born in Giza. He was a commentator on ancient Greek medicine, and in particular on Galen; his commentary on Galen's Ars Parva was translated by Gerardo Cremonese. However, he is better known for providing the most detailed description of the supernova now known as SN 1006, the brightest stellar event in recorded history, which he observed in the year 1006. This was written in a commentary on Ptolemy's work Tetrabiblos. He was later cited by European authors as Haly, or Haly Abenrudian. According to Alistair Cameron Crombie he also contributed to the theory of induction. He engaged in a celebrated polemic against another physician, Ibn Butlan of Baghdad.
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus.
Altair, also designated Alpha Aquilae (α Aquilae, abbreviated Alpha Aql, α Aql), is the brightest star in the constellation of Aquila and the twelfth brightest star in the night sky.
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).
Greek astronomy is astronomy written in the Greek language in classical antiquity.
Ancient Greek philosophy arose in the 6th century BC and continued throughout the Hellenistic period and the period in which Ancient Greece was part of the Roman Empire.
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.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.
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.
In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational equivalent of linear momentum.
Annie Jump Cannon (December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development of contemporary stellar classification.
The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
Arabic (العَرَبِيَّة) or (عَرَبِيّ) or) is a Central Semitic language that first emerged in Iron Age northwestern Arabia and is now the lingua franca of the Arab world. It is named after the Arabs, a term initially used to describe peoples living from Mesopotamia in the east to the Anti-Lebanon mountains in the west, in northwestern Arabia, and in the Sinai peninsula. Arabic is classified as a macrolanguage comprising 30 modern varieties, including its standard form, Modern Standard Arabic, which is derived from Classical Arabic. As the modern written language, Modern Standard Arabic is widely taught in schools and universities, and is used to varying degrees in workplaces, government, and the media. The two formal varieties are grouped together as Literary Arabic (fuṣḥā), which is the official language of 26 states and the liturgical language of Islam. Modern Standard Arabic largely follows the grammatical standards of Classical Arabic and uses much of the same vocabulary. However, it has discarded some grammatical constructions and vocabulary that no longer have any counterpart in the spoken varieties, and has adopted certain new constructions and vocabulary from the spoken varieties. Much of the new vocabulary is used to denote concepts that have arisen in the post-classical era, especially in modern times. During the Middle Ages, Literary Arabic was a major vehicle of culture in Europe, especially in science, mathematics and philosophy. As a result, many European languages have also borrowed many words from it. Arabic influence, mainly in vocabulary, is seen in European languages, mainly Spanish and to a lesser extent Portuguese, Valencian and Catalan, owing to both the proximity of Christian European and Muslim Arab civilizations and 800 years of Arabic culture and language in the Iberian Peninsula, referred to in Arabic as al-Andalus. Sicilian has about 500 Arabic words as result of Sicily being progressively conquered by Arabs from North Africa, from the mid 9th to mid 10th centuries. Many of these words relate to agriculture and related activities (Hull and Ruffino). Balkan languages, including Greek and Bulgarian, have also acquired a significant number of Arabic words through contact with Ottoman Turkish. Arabic has influenced many languages around the globe throughout its history. Some of the most influenced languages are Persian, Turkish, Spanish, Urdu, Kashmiri, Kurdish, Bosnian, Kazakh, Bengali, Hindi, Malay, Maldivian, Indonesian, Pashto, Punjabi, Tagalog, Sindhi, and Hausa, and some languages in parts of Africa. Conversely, Arabic has borrowed words from other languages, including Greek and Persian in medieval times, and contemporary European languages such as English and French in modern times. Classical Arabic is the liturgical language of 1.8 billion Muslims and Modern Standard Arabic is one of six official languages of the United Nations. All varieties of Arabic combined are spoken by perhaps as many as 422 million speakers (native and non-native) in the Arab world, making it the fifth most spoken language in the world. Arabic is written with the Arabic alphabet, which is an abjad script and is written from right to left, although the spoken varieties are sometimes written in ASCII Latin from left to right with no standardized orthography.
Aristyllus (Ἀρίστυλλος; fl. c. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c. 300 BC).
In observational astronomy, an asterism is a popular known pattern or group of stars that are recognised in the night sky.
Astrology is the study of the movements and relative positions of celestial objects as a means for divining information about human affairs and terrestrial events.
An astronomer is a scientist in the field of astronomy who concentrates their studies on a specific question or field outside the scope of Earth.
An astronomical constant is a physical constant used in astronomy.
An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.
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.
The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.
Astronomy (from ἀστρονομία) is a natural science that studies celestial objects and phenomena.
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.
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars.
The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of radio telescopes in the Atacama Desert of northern Chile.
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment.
Avempace (– 1138) is the Latinate form of Ibn Bâjja (ابن باجه), full name Abû Bakr Muḥammad Ibn Yaḥyà ibn aṣ-Ṣâ’igh at-Tûjîbî Ibn Bâjja al-Tujibi (أبو بكر محمد بن يحيى بن الصائغ), was an Arab Andalusian polymath: his writings include works regarding astronomy, physics, and music, as well as philosophy, medicine, botany, and poetry.
Babylon (KA2.DIĜIR.RAKI Bābili(m); Aramaic: בבל, Babel; بَابِل, Bābil; בָּבֶל, Bavel; ܒܒܠ, Bāwēl) was a key kingdom in ancient Mesopotamia from the 18th to 6th centuries BC.
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.
Babylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia.
Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing "Hoax" is a non-fiction book by the American astronomer Phil Plait, also known as "the Bad Astronomer".
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name.
Beryllium is a chemical element with symbol Be and atomic number 4.
A beta particle, also called beta ray or beta radiation, (symbol β) is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay.
Betelgeuse, also designated Alpha Orionis (α Orionis, abbreviated Alpha Ori, α Ori), is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion.
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
A binary star is a star system consisting of two stars orbiting around their common barycenter.
Binding energy (also called separation energy) is the minimum energy required to disassemble a system of particles into separate parts.
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.
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.
A blue dwarf is a predicted class of star that develops from a red dwarf after it has exhausted much of its hydrogen fuel supply.
A blue straggler is a main-sequence star in an open or globular cluster that is more luminous and bluer than stars at the main-sequence turn-off point for the cluster.
Blue supergiant stars are hot luminous stars, referred to scientifically as OB supergiants.
In astronomy, Bok globules are isolated and relatively small dark nebulae, containing dense cosmic dust and gas from which star formation may take place.
The Book of Fixed Stars (كتاب صور الكواكب) is an astronomical text written by Abd al-Rahman al-Sufi (Azophi) around 964.
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.
The British Library is the national library of the United Kingdom and the largest national library in the world by number of items catalogued.
Collinder 399 (Cr 399) is a random grouping of stars located in the constellation Vulpecula near the border with Sagitta.
Brown dwarfs are substellar objects that occupy the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter, or approximately to about.
Business is the activity of making one's living or making money by producing or buying and selling products (goods and services).
Cambridge University Press (CUP) is the publishing business of the University of Cambridge.
Canopus, also designated Alpha Carinae (α Carinae, abbreviated Alpha Car, α Car), is the brightest star in the southern constellation of Carina, and the second-brightest star in the night-time sky, after Sirius.
Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.
Carbon-12 is the more abundant of the two stable isotopes of carbon (Carbon-13 being the other), amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars.
The carbon-burning process or carbon fusion is a set of nuclear fusion reactions that take place in the cores of massive stars (at least 8 \beginsmallmatrixM_\odot\endsmallmatrix at birth) that combines carbon into other elements.
Cataclysmic variable stars (CV) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state.
Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalysthttp://goldbook.iupac.org/C00876.html, which is not consumed in the catalyzed reaction and can continue to act repeatedly.
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.
Celestial navigation, also known as astronavigation, is the ancient and modern practice of position fixing that enables a navigator to transition through a space without having to rely on estimated calculations, or dead reckoning, to know their position.
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others.
The centimetre–gram–second system of units (abbreviated CGS or cgs) is a variant of the metric system based on the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time.
The Centre de Données astronomiques de Strasbourg (CDS; English translation: Strasbourg Astronomical Data Center) is a data hub which collects and distributes astronomical information.
A Cepheid variable is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.
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).
In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers.
Astronomy in China has a long history, beginning from the Shang Dynasty (Chinese Bronze Age).
Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.
The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.
Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.
Christmas traditions vary from country to country.
Chromium is a chemical element with symbol Cr and atomic number 24.
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.
A civilization or civilisation (see English spelling differences) is any complex society characterized by urban development, social stratification imposed by a cultural elite, symbolic systems of communication (for example, writing systems), and a perceived separation from and domination over the natural environment.
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.
In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature.
In astronomy, a common envelope (CE) is gas that contains a binary star system.
In astronomy, the term "compact star" (or "compact object") refers collectively to white dwarfs, neutron stars, and black holes.
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture.
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes.
Convection is the heat transfer due to bulk movement of molecules within fluids such as gases and liquids, including molten rock (rheid).
A convection zone, convective zone or convective region of a star is a layer which is unstable to convection.
A corona (Latin, 'crown') is an aura of plasma that surrounds the Sun and other stars.
Coronal loops form the basic structure of the lower corona and transition region of the Sun.
Cosmic dust, also called extraterrestrial dust or space dust, is dust which exists in outer space, as well as all over planet Earth.
Islamic cosmology is the cosmology of Islamic societies.
Cosmos Redshift 7 (also known as COSMOS Redshift 7, Galaxy Cosmos Redshift 7, Galaxy CR7 or CR7) is a high-redshift Lyman-alpha emitter galaxy (meaning CR7 is one of the oldest, most distant galaxies), in the constellation Sextans, about 12.9 billion light travel distance years from Earth, reported to contain the first stars (first generation; Population III)—formed soon after the Big Bang during the reionisation epoch (redshift, z ∼ 6−7), when the Universe was about 800 million years old—to have provided the chemical elements (like oxygen, nitrogen, carbon, calcium and iron) needed for the later formation of planets and life as it is known.
The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus.
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.
Democritus (Δημόκριτος, Dēmókritos, meaning "chosen of the people") was an Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe.
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume.
Deuterium (or hydrogen-2, symbol or, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1).
The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source.
In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
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.
Edmond (or Edmund) Halley, FRS (–) was an English astronomer, geophysicist, mathematician, meteorologist, and physicist.
Prof Edward Charles Pickering FRS(For) HFRSE (July 19, 1846 – February 3, 1919) was an American astronomer and physicist and the older brother to William Henry Pickering.
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.
Egyptian astronomy begins in prehistoric times, in the Predynastic Period.
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space-time, carrying electromagnetic radiant energy.
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shell.
In physics, the electronvolt (symbol eV, also written electron-volt and electron volt) is a unit of energy equal to approximately joules (symbol J).
Energy flux is the rate of transfer of energy through a surface.
Epicurus (Ἐπίκουρος, Epíkouros, "ally, comrade"; 341–270 BC) was an ancient Greek philosopher who founded a school of philosophy now called Epicureanism.
Epsilon Indi (ε Indi, ε Ind) is a star system approximately 12 light-years from Earth in the constellation of Indus consisting of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it.
Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around 7,500 light-years (2,300 parsecs) distant in the constellation Carina.
An exoplanet or extrasolar planet is a planet outside our solar system.
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer.
Fairfield University is a private Jesuit Catholic research university located in the coastal town of Fairfield, Connecticut.
Fakhr al-Dīn al-Rāzī or Fakhruddin Razi (فخر الدين رازي) was an Iranian Sunni Muslim theologian and philosopher He was born in 1149 in Rey (in modern-day Iran), and died in 1209 in Herat (in modern-day Afghanistan).
First magnitude stars are the brightest stars in the night sky, with a magnitude of -1, 0 and +1.
A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England.
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes.
Frequency is the number of occurrences of a repeating event per unit of time.
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.
Friedrich Georg Wilhelm von Struve (Василий Яковлевич Струве, trans. Vasily Yakovlevich Struve; 15 April 1793 –) was a German-Russian astronomer and geodesist from the famous Struve family.
A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work.
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.
The Galactic Center is the rotational center of the Milky Way.
The Galactic Disc is a component of disc galaxies, such as spiral galaxies and lenticular galaxies.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
A gamma ray or gamma radiation (symbol γ or \gamma), is penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei.
A gas giant is a giant planet composed mainly of hydrogen and helium.
Geminiano Montanari. Geminiano Montanari (June 1, 1633 – October 13, 1687) was an Italian astronomer, lens-maker, and proponent of the experimental approach to science.
A giant star is a star with substantially larger radius and luminosity than a main-sequence (or dwarf) star of the same surface temperature.
Giordano Bruno (Iordanus Brunus Nolanus; 1548 – 17 February 1600), born Filippo Bruno, was an Italian Dominican friar, philosopher, mathematician, poet, and cosmological theorist.
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite.
In mathematics, the gradient is a multi-variable generalization of the derivative.
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.
The gravitational constant (also known as the "universal gravitational constant", the "Newtonian constant of gravitation", or the "Cavendish gravitational constant"), denoted by the letter, is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's general theory of relativity.
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect.
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.
Greek mythology is the body of myths and teachings that belong to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices.
The Gregorian calendar is the most widely used civil calendar in the world.
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized.
The Hayashi track is a luminosity–temperature relationship obeyed by infant stars of less than in the pre-main-sequence phase (PMS phase) of stellar evolution.
HD 140283, informally nicknamed the Methuselah star, is a metal-poor subgiant star about 200 light years away from the Earth in the constellation Libra, specifically toward Ophiuchus.
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems.
The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto.
Helium (from lit) is a chemical element with symbol He and atomic number 2.
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).
Helium-3 (He-3, also written as 3He, see also helion) is a light, non-radioactive isotope of helium with two protons and one neutron (common helium having two protons and two neutrons).
Helium-4 is a non-radioactive isotope of the element helium.
The Henyey track is a path taken by pre-main-sequence stars with masses >0.5 Solar mass in the Hertzsprung–Russell diagram after the end of Hayashi track.
A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young (V. Mannings & A. Sargent (2000) High-resolution studies of gas and dust around young intermediate-mass stars: II. observations of an additional sample of Herbig Ae/Be systems. Astrophysical Journal, vol. 529, p. 391 Hydrogen and calcium emission lines are observed in their spectra. They are 2-8 Solar mass objects, still existing in the star formation (gravitational contraction) stage and approaching the main sequence (i.e. they are not burning hydrogen in their center). In the Hertzsprung–Russell diagram these stars are located to the right of the main sequence. They are named after the American astronomer George Herbig, who first distinguished them from other stars in 1960. The original Herbig criteria were.
Herbig–Haro (HH) objects are turbulent looking patches of nebulosity associated with newborn stars.
The Hertzsprung–Russell diagram, abbreviated H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures.
Hipparchus of Nicaea (Ἵππαρχος, Hipparkhos) was a Greek astronomer, geographer, and mathematician.
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.
The human eye is an organ which reacts to light and pressure.
Hydrogen is a chemical element with symbol H and atomic number 1.
The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.
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.
A hypergiant (luminosity class 0 or Ia+) is among the very rare kinds of stars that typically show tremendous luminosities and very high rates of mass loss by stellar winds.
The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community.
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.
Interacting galaxies (colliding galaxies) are galaxies whose gravitational fields result in a disturbance of one another.
Interferometry is a family of techniques in which waves, usually electromagnetic waves, are superimposed causing the phenomenon of interference in order to extract information.
The International Astronomical Union (IAU; Union astronomique internationale, UAI) is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy.
The International Star Registry (ISR) is an organization founded in 1979 for the purpose of giving people the novelty of officially naming stars.
The International System of Units (SI, abbreviated from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement.
In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.
Inverse beta decay, commonly abbreviated to IBD, is a nuclear reaction involving electron antineutrino scattering off a proton, creating a positron and a neutron.
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).
Iron is a chemical element with symbol Fe (from ferrum) and atomic number 26.
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.
Isis is a quarterly peer-reviewed academic journal published by the University of Chicago Press.
The Islamic, Muslim, or Hijri calendar (التقويم الهجري at-taqwīm al-hijrī) is a lunar calendar consisting of 12 months in a year of 354 or 355 days.
Beryllium (4Be) has 12 known isotopes, but only one of these isotopes is stable and a primordial nuclide.
Hydrogen (1H) has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H.
In stellar physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation.
Johann Bayer (1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer).
John Flamsteed FRS (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal.
Sir John Frederick William Herschel, 1st Baronet (7 March 1792 – 11 May 1871) was an English polymath, mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint, and did botanical work.
Joseph Ritter von Fraunhofer (6 March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer.
Jupiter is the fifth planet from the Sun and the largest in the Solar System.
Karl Schwarzschild (October 9, 1873 – May 11, 1916) was a German physicist and astronomer.
The Kassites were people of the ancient Near East, who controlled Babylonia after the fall of the Old Babylonian Empire c. 1531 BC and until c. 1155 BC (short chronology).
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.
The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way.
Latin (Latin: lingua latīna) is a classical language belonging to the Italic branch of the Indo-European languages.
In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface.
LBV 1806-20 is a candidate luminous blue variable (LBV) and likely binary star located nearly 40,000 light-years from the Sun, towards the center of the Milky Way.
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.
The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.
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.
This is a list of traditional Arabic names for stars.
Below is an ordered list of the largest stars currently known by radius.
The following are lists of stars.
Lithium (from lit) is a chemical element with symbol Li and atomic number 3.
The Local Group is the galaxy group that includes the Milky Way.
A logarithmic scale is a nonlinear scale used when there is a large range of quantities.
In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.
A lunar eclipse occurs when the Moon passes directly behind Earth and into its shadow.
Luyten 726-8, also known as Gliese 65, is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus.
MACS J1149 Lensed Star 1, also known as Icarus,Other names include LS1, MACS J1149 LS1, MACS J1149 Lensed Star 1 (LS1) and MACS J1149+2223 Lensed Star 1 is a blue supergiant observed through a gravitational lens.
A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.
In astronomy, the main sequence is a continuous and distinctive band of stars that appear on plots of stellar color versus brightness.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.
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.
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.
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.
Mercury is the smallest and innermost planet in the Solar System.
Mesopotamia is a historical region in West Asia situated within the Tigris–Euphrates river system, in modern days roughly corresponding to most of Iraq, Kuwait, parts of Northern Saudi Arabia, the eastern parts of Syria, Southeastern Turkey, and regions along the Turkish–Syrian and Iran–Iraq borders.
In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.
The Milky Way is the galaxy that contains our Solar System.
A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to of one degree.
Mira variables ("Mira", Latin, adj. - feminine form of adjective "wonderful"), named for the prototype star Mira, are a class of pulsating variable stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths.
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).
Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States.
Mu Leonis (μ Leonis, abbreviated Mu Leo, μ Leo), also named Rasalas, is a star in the constellation of Leo.
Mythology refers variously to the collected myths of a group of people or to the study of such myths.
This article lists and discusses the usage and derivation of names of large numbers, together with their possible extensions.
Nature is a British multidisciplinary scientific journal, first published on 4 November 1869.
A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases.
Neon is a chemical element with symbol Ne and atomic number 10.
The neon-burning process (nuclear decay) is a set of nuclear fusion reactions that take place in massive stars (at least 8 Solar masses).
Neptune is the eighth and farthest known planet from the Sun in the Solar System.
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.
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.
New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.
The New York City Department of Consumer Affairs (DCA) is an agency of the Government of New York City.
NGC 6397, also known as Caldwell 86, is a globular cluster in the constellation Ara.
The term night sky, usually associated with astronomy from Earth, refers to the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon.
A nova (plural novae or novas) or classical nova (CN, plural CNe) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or many months.
In mathematics, an nth root of a number x, where n is usually assumed to be a positive integer, is a number r which, when raised to the power n yields x: where n is the degree of the root.
In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).
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).
An O-type star is a hot, blue-white star of spectral type O in the Yerkes classification system employed by astronomers.
The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion.
An observatory is a location used for observing terrestrial or celestial events.
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.
Omicron Velorum (ο Vel, ο Velorum) is a star in the constellation Vela.
Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light.
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.
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.
Orbital elements are the parameters required to uniquely identify a specific orbit.
Orion is a prominent constellation located on the celestial equator and visible throughout the world.
The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion.
Outer space, or just space, is the expanse that exists beyond the Earth and between celestial bodies.
The following outline is provided as an overview of and topical guide to astronomy: Astronomy – studies the universe beyond Earth, including its formation and development, and the evolution, physics, chemistry, meteorology, and motion of celestial objects (such as galaxies, planets, etc.) and phenomena that originate outside the atmosphere of Earth (such as the cosmic background radiation).
Oxygen is a chemical element with symbol O and atomic number 8.
The oxygen-burning process is a set of nuclear fusion reactions that take place in massive stars that have used up the lighter elements in their cores.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.
Particle radiation is the radiation of energy by means of fast-moving subatomic particles.
The Persians--> are an Iranian ethnic group that make up over half the population of Iran.
The photoelectric effect is the emission of electrons or other free carriers when light shines on a material.
A photograph or photo is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic medium such as a CCD or a CMOS chip.
Before the advent of photometers which accurately measure the brightness of astronomical objects, the apparent magnitude of an object was obtained by taking a picture of it with a camera.
A photometer, generally, is an instrument that measures light intensity or the optical properties of solutions or surfaces.
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).
The photosphere is a star's outer shell from which light is radiated.
Planck was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013, which mapped the anisotropies of the cosmic microwave background (CMB) at microwave and infra-red frequencies, with high sensitivity and small angular resolution.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
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.
A planetary system is a set of gravitationally bound non-stellar objects in or out of orbit around a star or star system.
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.
A polymath (πολυμαθής,, "having learned much,"The term was first recorded in written English in the early seventeenth century Latin: uomo universalis, "universal man") is a person whose expertise spans a significant number of different subject areas—such a person is known to draw on complex bodies of knowledge to solve specific problems.
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron.
In physics, power is the rate of doing work, the amount of energy transferred per unit time.
A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence.
In atmospheric science (meteorology, climatology and related fields), the pressure gradient (typically of air, more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location.
Procyon, also designated Alpha Canis Minoris (α Canis Minoris, abbreviated Alpha CMi, α CMi), is the brightest star in the constellation of Canis Minor.
Proper motion is the astronomical measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars.
The proton–proton chain reaction is one of the two (known) sets of fusion reactions by which stars convert hydrogen to helium.
A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star.
A protostar is a very young star that is still gathering mass from its parent molecular cloud.
Proxima Centauri, or Alpha Centauri C, is a red dwarf, a small low-mass star, about from the Sun in the constellation of Centaurus.
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.
A pulsar (from pulse and -ar as in quasar) is a highly magnetized rotating neutron star or white dwarf that emits a beam of electromagnetic radiation.
Quark matter or QCD matter refers to any of a number of theorized phases of matter whose degrees of freedom include quarks and gluons.
Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.
R Doradus (HD 29712 or P Doradus) is the name of a red giant Mira variable star in the far-southern constellation Dorado, although visually it appears more closely associated with the constellation Reticulum.
R136 (formally known as RMC 136 from the Radcliffe Observatory Magellanic Clouds catalogue) is the central concentration of stars in the NGC 2070 star cluster, which lies at the centre of the Tarantula Nebula in the Large Magellanic Cloud.
The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point.
In physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic and gravitational 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.
Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field.
A radiation zone, radiative zone or radiative region is a layer of a star's interior where energy is primarily transported toward the exterior by means of radiative diffusion and thermal conduction, rather than by convection.
Radio frequency (RF) refers to oscillatory change in voltage or current in a circuit, waveguide or transmission line in the range extending from around twenty thousand times per second to around three hundred billion times per second, roughly between the upper limit of audio and the lower limit of infrared.
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.
A rare-earth element (REE) or rare-earth metal (REM), as defined by IUPAC, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium.
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.
A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.
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.
Red supergiants are stars with a supergiant luminosity class (Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous.
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.
In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.
Refraction is the change in direction of wave propagation due to a change in its transmission medium.
Regulation is an abstract concept of management of complex systems according to a set of rules and trends.
In the field of Big Bang theory, and cosmology, reionization is the process that caused the matter in the universe to reionize after the lapse of the "dark ages".
Richard Bentley (27 January 1662 – 14 July 1742) was an English classical scholar, critic, and theologian.
Rigel, also designated Beta Orionis (β Orionis, abbreviated Beta Ori, β Ori), is generally the seventh-brightest star in the night sky and the brightest star in the constellation of Orion—though periodically it is outshone within the constellation by the variable Betelgeuse.
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.
The Roche lobe (or Roche limit) is the region around a star in a binary system within which orbiting material is gravitationally bound to that star.
Roman mythology is the body of traditional stories pertaining to ancient Rome's legendary origins and religious system, as represented in the literature and visual arts of the Romans.
A rotation is a circular movement of an object around a center (or point) of rotation.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.
The second is the SI base unit of time, commonly understood and historically defined as 1/86,400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each.
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the widest points of the perimeter.
Sherburne Wesley Burnham (December 12, 1838 – March 11, 1921) was an American astronomer.
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance.
Sidereal time is a timekeeping system that astronomers use to locate celestial objects.
Silicon is a chemical element with symbol Si and atomic number 14.
In astrophysics, silicon burning is a very brief sequence of nuclear fusion reactions that occur in massive stars with a minimum of about 8-11 solar masses.
Sirius (a romanization of Greek Σείριος, Seirios,."glowing" or "scorching") is a star system and the brightest star in the Earth's night sky.
SN 1006 was a supernova that is likely the brightest observed stellar event in recorded history, reaching an estimated −7.5 visual magnitude, and exceeding roughly sixteen times the brightness of Venus.
SN 1054 is a supernova that was first observed on 4 July 1054, and remained visible for around two years.
SN 185 was a transient astronomical event observed in AD 185, likely a supernova.
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.
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.
A solar flare is a sudden flash of increased Sun's brightness, usually observed near its surface.
The solar luminosity,, is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
The solar mass is a standard unit of mass in astronomy, equal to approximately.
Solar radius is a unit of distance used to express the size of stars in astronomy.
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona.
The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration (NASA), as part of the Space Shuttle program.
Space.com is a space and astronomy news website.
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.
Spectroscopy is the study of the interaction between matter and electromagnetic radiation.
A spheroid, or ellipsoid of revolution, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters.
In solar physics, a spicule is a dynamic jet of about 500 km diameter in the chromosphere of the Sun.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.
The Stanford Encyclopedia of Philosophy (SEP) combines an online encyclopedia of philosophy with peer-reviewed publication of original papers in philosophy, freely accessible to Internet users.
A star catalogue (Commonwealth English) or star catalog (American English), is an astronomical catalogue that lists stars.
A star chart or star map, also called a sky chart or sky map, is a map of the night sky.
A star clock (or nocturnal) is a method of using the stars to determine the time.
Star clusters are groups of stars.
Star counts are bookkeeping surveys of stars and the statistical and geometrical methods used to correct the survey data for bias.
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.
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction.
A starburst galaxy is a galaxy undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies.
The planetary systems of stars other than the Sun and the Solar System are a staple element in many works of the science fiction genre.
Starspots are stellar phenomena.
A stellar association is a very loose star cluster, looser than both open clusters and globular clusters.
The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone.
In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
Designations and names of stars (and other celestial bodies) are currently primarily mediated in the scientific community by the International Astronomical Union (IAU), a de facto authority.
Stellar dynamics is the branch of astrophysics which describes in a statistical way the collective motions of stars subject to their mutual gravity.
Stellar evolution is the process by which a star changes over the course of time.
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar mass is a phrase that is used by astronomers to describe the mass of a star.
Stellar nucleosynthesis is the theory explaining the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions between atoms within the stars.
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.
A stellar wind is a flow of gas ejected from the upper atmosphere of a star.
Students for the Exploration and Development of Space (SEDS) is an international student organization whose purpose is to promote space exploration and development through educational and engineering projects.
The Sun is the star at the center of the Solar System.
Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas.
Supergiants are among the most massive and most luminous stars.
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.
Supernova nucleosynthesis is a theory of the nucleosynthesis of the natural abundances of the chemical elements in supernova explosions, advanced as the nucleosynthesis of elements from carbon to nickel in massive stars by Fred Hoyle in 1954.
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova.
The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface.
T Tauri stars (TTS) are a class of variable stars associated with youth.
A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).
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.
The New York Times (sometimes abbreviated as The NYT or The Times) is an American newspaper based in New York City with worldwide influence and readership.
Two physical systems are in thermal equilibrium if there are no net flow of thermal energy between them when they are connected by a path permeable to heat.
Thermonuclear fusion is a way to achieve nuclear fusion by using extremely high temperatures.
Timocharis of Alexandria (Τιμόχαρις or Τιμοχάρης, gen. Τιμοχάρους; c. 320–260 BC) was a Greek astronomer and philosopher.
The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon.
"Twinkle, Twinkle, Little Star" is a popular English lullaby.
Twinkling, or scintillation, is a generic term for variations in apparent brightness or position of a distant luminous object viewed through a medium.
Tycho Brahe (born Tyge Ottesen Brahe;. He adopted the Latinized form "Tycho Brahe" (sometimes written Tÿcho) at around age fifteen. The name Tycho comes from Tyche (Τύχη, meaning "luck" in Greek, Roman equivalent: Fortuna), a tutelary deity of fortune and prosperity of ancient Greek city cults. He is now generally referred to as "Tycho," as was common in Scandinavia in his time, rather than by his surname "Brahe" (a spurious appellative form of his name, Tycho de Brahe, only appears much later). 14 December 154624 October 1601) was a Danish nobleman, astronomer, and writer known for his accurate and comprehensive astronomical and planetary observations.
A type Ia supernova (read "type one-a") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf.
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.
Unfair business practices encompass fraud, misrepresentation, and oppressive or unconscionable acts or practices by business, often against consumers and are prohibited by law in many countries.
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
The University of California (UC) is a public university system in the US state of California.
Uranus is the seventh planet from the Sun.
A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump.
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.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile.
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo.
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which in turn contains the Milky Way and Andromeda galaxies.
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter.
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.
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon.
X-rays make up X-radiation, a form of electromagnetic radiation.
X-ray bursters are one class of X-ray binary stars exhibiting periodic and rapid increases in luminosity (typically a factor of 10 or greater) that peak in the X-ray regime of the electromagnetic spectrum.
Yale University Press is a university press associated with Yale University.
Zeta Ophiuchi (ζ Oph, ζ Ophiuchi) is a star located in the constellation of Ophiuchus.
Mizar is a 2nd magnitude star in the handle of the Big Dipper asterism in the constellation of Ursa Major.
A zīj (زيج) is an Islamic astronomical book that tabulates parameters used for astronomical calculations of the positions of the Sun, Moon, stars, and planets.
14 Herculis or 14 Her is the Flamsteed designation of a K-type main-sequence star approximately 57 light-years away in the constellation Hercules.
2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.
2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.
2MASS J0523-1403 is a very-low-mass red dwarf about 40 light years from Earth in the southern constellation of Lepus.
61 Cygni Not to be confused with 16 Cygni, a more distant system containing two G-type stars harboring the gas giant planet 16 Cygni Bb.