344 relations: Abū Ishāq Ibrāhīm al-Zarqālī, Abd al-Rahman al-Sufi, Abu Maʿshar, Academic Press, Active galactic nucleus, Age of the universe, Air mass (astronomy), Al-Battani, Al-Birjandi, Al-Biruni, Alexis Clairaut, Ali ibn Ridwan, Amateur astronomy, Amateur telescope making, Amplitude, Analog computer, Ancient Greece, Ancient Greek, Ancient Greek astronomy, Andromeda Galaxy, Anthropology, Antikythera mechanism, Apparent magnitude, Archaeoastronomy, Archaeology, Aristarchus of Samos, Asteroid, Asteroid belt, Astrobiology, Astrochemistry, Astrolabe, Astrology, Astrology and astronomy, Astrology in medieval Islam, Astrometry, Astronomer, Astronomical clock, Astronomical object, Astronomy & Astrophysics, Astronomy Camp, Astronomy in the medieval Islamic world, Astroparticle physics, Astrophotography, Astrophysical X-ray source, Astrophysics, Astrophysics Data System, Astrostatistics, Atmosphere, Atmosphere of Earth, Atom, ..., Aurora, Ångström, Babylonian astronomy, Barred spiral galaxy, Big Bang, Big Bang nucleosynthesis, Binary black hole, Black hole, Black-body radiation, Blazar, Book of Fixed Stars, Bremsstrahlung, Calendar, California Institute of Technology, Celestial mechanics, Celestial navigation, Chambers Book of Days, Charge-coupled device, Chemical substance, Chemistry, Chinese astronomy, Chromosphere, Chronology of the universe, Circumstellar disc, CNO cycle, Comet, Compton Gamma Ray Observatory, Computation, Constellation, Convection zone, Corona, Cosmic Background Explorer, Cosmic distance ladder, Cosmic dust, Cosmic microwave background, Cosmic ray, Cosmochemistry, Cosmogony, Cosmology, CRC Press, Dark energy, Dark matter, Dark matter halo, Dark nebula, Deep-sky object, Doppler spectroscopy, Dwarf planet, Dwarf star, Earth, Earth's magnetic field, Egyptian astronomy, Electromagnetic radiation, Electromagnetic spectrum, Electron, Ellipse, Elliptical galaxy, Erosion, Europe, Event horizon, Exoplanet, Expansion of the universe, Extraterrestrial life, Fermi paradox, First observation of gravitational waves, Flatness problem, Forensic astronomy, Frank Shu, Friedrich Bessel, Galaxy, Galaxy filament, Galaxy formation and evolution, Galaxy groups and clusters, Galaxy morphological classification, Galileo Galilei, GALLEX, Gamma ray, Gamma-ray burst, Gas giant, General relativity, Geocentric model, Giant-impact hypothesis, Globular cluster, Gravitational collapse, Gravitational wave, Gravitational-wave astronomy, Gravitational-wave observatory, Gravity, Great Zimbabwe, Gustav Kirchhoff, H II region, Heliocentrism, Heliosphere, Helium, Hellenistic period, High-altitude balloon, Hipparchus, Hubble Space Telescope, Hubble's law, Hydrogen, IACT, Impact crater, Indian astronomy, Indigenous peoples of the Americas, Inflation (cosmology), Infrared, Initial mass function, International Year of Astronomy, Interstellar medium, Iranian peoples, Irregular galaxy, Isaac Newton, Isis (journal), Isotope, Jean le Rond d'Alembert, Jeans instability, Johannes Kepler, John Flamsteed, Joseph von Fraunhofer, Joseph-Louis Lagrange, Journal of Astronomical History and Heritage, Jupiter, Kamioka Observatory, Karl Guthe Jansky, Kelvin, Kuiper belt, Lambda-CDM model, Leonhard Euler, Light, LIGO, LIGO Scientific Collaboration, Linda Hall Library, List of Arabic star names, List of astronomical instruments, List of astronomy acronyms, List of Russian astronomers and astrophysicists, Little Ice Age, Local Group, Lunar eclipse, Magnetic field, Magnetosphere, Main sequence, Maragheh observatory, Mars, Mass, Mathematical model, Mathematics, Matter, Maunder Minimum, Maya civilization, Mercury (planet), Metallicity, Meteor shower, Middle Ages, Milky Way, Molecular cloud, Moon, Multi-messenger astronomy, Muslim world, Nanometre, NASA, Natural satellite, Natural science, Near-Earth object, Neptune, Neutrino, Neutrino astronomy, Neutrino detector, Neutron star, Nicolas-Louis de Lacaille, Nicolaus Copernicus, Night sky, Nordtvedt effect, Nubians, Nuclear fusion, Nucleocosmochronology, Nucleosynthesis, Numerical analysis, OB star, Observable universe, Observational astronomy, Observatory, On the Sizes and Distances (Aristarchus), One-Mile Telescope, Oort cloud, Open cluster, Optical spectrometer, Outline of space science, Parallax, Perturbation theory, Phase (waves), Phenomenon, Philosophical Transactions of the Royal Society, Photon, Photosphere, Physical cosmology, Physical Review Letters, Physics, Pierre-Simon Laplace, Planet, Planetary differentiation, Planetary nebula, Pre-stellar core, Precession, Proper motion, Protoplanetary disk, Protostar, Ptolemy, Pulsar, Quantum fluctuation, Quasar, Radial velocity, Radiation pressure, Radiation zone, Radio, Radio galaxy, Radio telescope, Radio wave, Randomness, Realencyclopädie der classischen Altertumswissenschaft, Recorded history, Red giant, Reflecting telescope, Reionization, Renaissance, Rocket, SAGE (Soviet–American Gallium Experiment), Saros (astronomy), Saturn, Seyfert galaxy, SN 1006, SN 1987A, Solar cycle, Solar System, Solar wind, Space exploration, Space telescope, Spectral line, Spectroscopy, Spiral galaxy, Star, Star cluster, Star formation, Star system, Stellar classification, Stellar collision, Stellar dynamics, Stellar evolution, Stellar parallax, Stellar population, String theory, Sub-Saharan Africa, Sun, Supercluster, Supermassive black hole, Supernova, Supernova remnant, Synchrotron radiation, Temperature, Terrestrial planet, Thābit ibn Qurra, The Astronomical Journal, The Astrophysical Journal, Theoretical astronomy, Thorium, Three-body problem, Tidal acceleration, Timbuktu, Ultimate fate of the universe, Ultra-high-energy cosmic ray, Ultraviolet, Ulugh Beg Observatory, Universe, Universe: The Infinite Frontier, University of California, Berkeley, University of St Andrews, University of Virginia, Uranium, Uranus, Van Allen radiation belt, Variable star, Venus, Void (astronomy), Volcanism, Wave, Wavelength, White dwarf, Wide-field Infrared Survey Explorer, William Herschel, Wolf number, X-ray, X-ray astronomy, X-ray astronomy satellite, X-ray binary, 61 Cygni. 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, also known as Al-Zarkali or Ibn Zarqala (1029–1087), was an Arab Muslim instrument maker, astrologer, and one of the leading astronomers of his time.
'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.
Abu Maʿshar, Latinized as Albumasar (also Albusar, Albuxar; full name Abū Maʿshar Jaʿfar ibn Muḥammad ibn ʿUmar al-Balkhī أبو معشر جعفر بن محمد بن عمر البلخي; –, AH 171–272), was an early Persian Muslim astrologer, thought to be the greatest astrologer of the Abbasid court in Baghdad.
Academic Press is an academic book publisher.
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion—and possibly all—of the electromagnetic spectrum, with characteristics indicating that the excess luminosity is not produced by stars.
In physical cosmology, the age of the universe is the time elapsed since the Big Bang.
In astronomy, air mass (airmass, or AM) is the path length for light from a celestial source to pass through the atmosphere.
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.
Abd Ali ibn Muhammad ibn Husayn Birjandi (عبدعلی محمد بن حسین بیرجندی) (died 1528) was a prominent 16th-century Persian astronomer, mathematician and physicist who lived in Birjand.
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.
Alexis Claude Clairaut (13 May 1713 – 17 May 1765) was a French mathematician, astronomer, and geophysicist.
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.
Amateur astronomy is a hobby whose participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes.
Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional.
The amplitude of a periodic variable is a measure of its change over a single period (such as time or spatial period).
An analog computer or analogue computer is a form of computer that uses the continuously changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved.
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).
The Ancient Greek language includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD.
Greek astronomy is astronomy written in the Greek language in classical antiquity.
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.
Anthropology is the study of humans and human behaviour and societies in the past and present.
The Antikythera mechanism is an ancient Greek analogue computer and orrery used to predict astronomical positions and eclipses for calendar and astrological purposes decades in advance.
The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
Archaeoastronomy (also spelled archeoastronomy) is the study of how people in the past "have understood the phenomena in the sky, how they used these phenomena and what role the sky played in their cultures".
Archaeology, or archeology, is the study of humanactivity through the recovery and analysis of material culture.
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).
Asteroids are minor planets, especially those of the inner Solar System.
The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter.
Astrobiology is a branch of biology concerned with the origins, early evolution, distribution, and future of life in the universe.
Astrochemistry is the study of the abundance and reactions of molecules in the Universe, and their interaction with radiation.
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.
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.
Astrology and astronomy were archaically treated together (astrologia), and were only gradually separated in Western 17th century philosophy (the "Age of Reason") with the rejection of astrology.
The medieval Muslims took a keen interest in the study of heavens: partly because they considered the celestial bodies to be divine, partly because the dwellers of desert-regions often travelled at night, and relied upon knowledge of the constellations for guidance in their journeys.
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
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 clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.
An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.
Astronomy & Astrophysics is a peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics.
Astronomy Camp is a science summer camp hosted by the University of Arizona's Alumni Association, and run by astronomer Don McCarthy.
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.
Astroparticle physics, also called particle astrophysics, is a branch of particle physics that studies elementary particles of astronomical origin and their relation to astrophysics and cosmology.
Astrophotography is a specialized type of photography for recording photos of astronomical objects, celestial events, and areas of the night sky.
Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.
Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space".
The Astrophysics Data System (ADS) is an online database of over eight million astronomy and physics papers from both peer reviewed and non-peer reviewed sources.
Astrostatistics is a discipline which spans astrophysics, statistical analysis and data mining.
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
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.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
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).
The ångström or angstrom is a unit of length equal to (one ten-billionth of a metre) or 0.1 nanometre.
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.
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars.
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
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.
A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other.
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.
Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body).
A blazar is a very compact quasar (quasi-stellar radio source) associated with a presumed supermassive black hole at the center of an active, giant elliptical galaxy.
The Book of Fixed Stars (كتاب صور الكواكب) is an astronomical text written by Abd al-Rahman al-Sufi (Azophi) around 964.
Bremsstrahlung, from bremsen "to brake" and Strahlung "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus.
A calendar is a system of organizing days for social, religious, commercial or administrative purposes.
The California Institute of Technology (abbreviated Caltech)The university itself only spells its short form as "Caltech"; other spellings such as.
Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects.
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.
Chambers Book of Days (The Book of Days: A Miscellany of Popular Antiquities in Connection with the Calendar, Including Anecdote, Biography, & History, Curiosities of Literature and Oddities of Human Life and Character) was written by the Scottish author Robert Chambers and first published in 1864.
A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value.
A chemical substance, also known as a pure substance, is a form of matter that consists of molecules of the same composition and structure.
Chemistry is the scientific discipline involved with compounds composed of atoms, i.e. elements, and molecules, i.e. combinations of atoms: their composition, structure, properties, behavior and the changes they undergo during a reaction with other compounds.
Astronomy in China has a long history, beginning from the Shang Dynasty (Chinese Bronze Age).
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.
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.
A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a star.
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.
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.
The Compton Gamma Ray Observatory (CGRO) was a space observatory detecting photons with energies from 20 keV to 30 GeV, in Earth orbit from 1991 to 2000.
Computation is any type of calculation that includes both arithmetical and non-arithmetical steps and follows a well-defined model, for example an algorithm.
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.
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.
The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was a satellite dedicated to cosmology, which operated from 1989 to 1993.
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects.
Cosmic dust, also called extraterrestrial dust or space dust, is dust which exists in outer space, as well as all over planet Earth.
The cosmic microwave background (CMB, CMBR) is electromagnetic radiation as a remnant from an early stage of the universe in Big Bang cosmology.
Cosmic rays are high-energy radiation, mainly originating outside the Solar System and even from distant galaxies.
Cosmochemistry (from Greek κόσμος kósmos, "universe" and χημεία khemeía) or chemical cosmology is the study of the chemical composition of matter in the universe and the processes that led to those compositions.
Cosmogony is any model concerning the origin of either the cosmos or universe.
Cosmology (from the Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is the study of the origin, evolution, and eventual fate of the universe.
The CRC Press, LLC is a publishing group based in the United States that specializes in producing technical books.
In physical cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe.
Dark matter is a theorized form of matter that is thought to account for approximately 80% of the matter in the universe, and about a quarter of its total energy density.
A dark matter halo is a hypothetical component of a galaxy that envelops the galactic disc and extends well beyond the edge of the visible galaxy.
A dark nebula or absorption nebula is a type of interstellar cloud that is so dense that it obscures the light from objects behind it, such as background stars and emission or reflection nebulae.
Deep-sky object (abbreviated as DSO) is a term designating any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.). The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as star clusters, nebulae and galaxies.
Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.
A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite.
A dwarf star is a star of relatively small size and low luminosity.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it meets the solar wind, a stream of charged particles emanating from the Sun.
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.
The electron is a subatomic particle, symbol or, whose electric charge is negative one elementary charge.
In mathematics, an ellipse is a curve in a plane surrounding two focal points such that the sum of the distances to the two focal points is constant for every point on the curve.
An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless image.
In earth science, erosion is the action of surface processes (such as water flow or wind) that remove soil, rock, or dissolved material from one location on the Earth's crust, and then transport it to another location (not to be confused with weathering which involves no movement).
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere.
In general relativity, an event horizon is a region in spacetime beyond which events cannot affect an outside observer.
An exoplanet or extrasolar planet is a planet outside our solar system.
The expansion of the universe is the increase of the distance between two distant parts of the universe with time.
Extraterrestrial life,Where "extraterrestrial" is derived from the Latin extra ("beyond", "not of") and terrestris ("of Earth", "belonging to Earth").
The Fermi paradox, or Fermi's paradox, named after physicist Enrico Fermi, is the apparent contradiction between the lack of evidence and high probability estimates for the existence of extraterrestrial civilizations.
The first observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016.
The flatness problem (also known as the oldness problem) is a cosmological fine-tuning problem within the Big Bang model of the universe.
Forensic astronomy is the use of astronomy, the scientific study of celestial objects, to determine the appearance of the sky at specific times in the past.
Frank H. Shu (born June2, 1943), is an American astrophysicist, astronomer and author.
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
The distribution reveals fine, filamentary structures.
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies.
Galaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation.
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance.
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.
GALLEX or Gallium Experiment was a radiochemical neutrino detection experiment that ran between 1991 and 1997 at the Laboratori Nazionali del Gran Sasso (LNGS).
A gamma ray or gamma radiation (symbol γ or \gamma), is penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei.
In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic explosions that have been observed in distant galaxies.
A gas giant is a giant planet composed mainly of hydrogen and helium.
General relativity (GR, also known as the general theory of relativity or GTR) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.
In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe with Earth at the center.
The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago, in the Hadean eon; about 20 to 100 million years after the solar system coalesced.
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite.
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.
Gravitational waves are the disturbance in the fabric ("curvature") of spacetime generated by accelerated masses and propagate as waves outward from their source at the speed of light.
Gravitational-wave astronomy is an emerging branch of observational astronomy which aims to use gravitational waves (minute distortions of spacetime predicted by Einstein's theory of general relativity) to collect observational data about objects such as neutron stars and black holes, events such as supernovae, and processes including those of the early universe shortly after the Big Bang.
A gravitational-wave observatory (or gravitational-wave detector) is any device designed to measure gravitational waves, tiny distortions of spacetime that were first predicted by Einstein in 1916.
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.
Great Zimbabwe is a medieval city in the south-eastern hills of Zimbabwe near Lake Mutirikwe and the town of Masvingo.
Gustav Robert Kirchhoff (12 March 1824 – 17 October 1887) was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects.
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized.
Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System.
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.
The Hellenistic period covers the period of Mediterranean history between the death of Alexander the Great in 323 BC and the emergence of the Roman Empire as signified by the Battle of Actium in 31 BC and the subsequent conquest of Ptolemaic Egypt the following year.
High-altitude balloons are manned or unmanned balloons, usually filled with helium or hydrogen and rarely methane, that are released into the stratosphere, generally attaining between.
Hipparchus of Nicaea (Ἵππαρχος, Hipparkhos) was a Greek astronomer, geographer, and mathematician.
The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.
Hubble's law is the name for the observation in physical cosmology that.
Hydrogen is a chemical element with symbol H and atomic number 1.
IACT stands for Imaging Atmospheric (or Air) Cherenkov Telescope or Technique.
An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body.
Indian astronomy has a long history stretching from pre-historic to modern times.
The indigenous peoples of the Americas are the pre-Columbian peoples of the Americas and their descendants. Although some indigenous peoples of the Americas were traditionally hunter-gatherers—and many, especially in the Amazon basin, still are—many groups practiced aquaculture and agriculture. The impact of their agricultural endowment to the world is a testament to their time and work in reshaping and cultivating the flora indigenous to the Americas. Although some societies depended heavily on agriculture, others practiced a mix of farming, hunting and gathering. In some regions the indigenous peoples created monumental architecture, large-scale organized cities, chiefdoms, states and empires. Many parts of the Americas are still populated by indigenous peoples; some countries have sizable populations, especially Belize, Bolivia, Canada, Chile, Ecuador, Greenland, Guatemala, Guyana, Mexico, Panama and Peru. At least a thousand different indigenous languages are spoken in the Americas. Some, such as the Quechuan languages, Aymara, Guaraní, Mayan languages and Nahuatl, count their speakers in millions. Many also maintain aspects of indigenous cultural practices to varying degrees, including religion, social organization and subsistence practices. Like most cultures, over time, cultures specific to many indigenous peoples have evolved to incorporate traditional aspects but also cater to modern needs. Some indigenous peoples still live in relative isolation from Western culture, and a few are still counted as uncontacted peoples.
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe.
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.
In astronomy, the initial mass function (IMF) is an empirical function that describes the initial distribution of masses for a population of stars.
The International Year of Astronomy (IYA2009) was a year-long celebration of astronomy that took place in 2009 to coincide with the 400th anniversary of the first recorded astronomical observations with a telescope by Galileo Galilei and the publication of Johannes Kepler's Astronomia nova in the 17th century.
In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.
The Iranian peoples, or Iranic peoples, are a diverse Indo-European ethno-linguistic group that comprise the speakers of the Iranian languages.
An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.
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.
Isotopes are variants of a particular chemical element which differ in neutron number.
Jean-Baptiste le Rond d'Alembert (16 November 1717 – 29 October 1783) was a French mathematician, mechanician, physicist, philosopher, and music theorist.
In stellar physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation.
Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer, and astrologer.
John Flamsteed FRS (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal.
Joseph Ritter von Fraunhofer (6 March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer.
Joseph-Louis Lagrange (or;; born Giuseppe Lodovico Lagrangia, Encyclopædia Britannica or Giuseppe Ludovico De la Grange Tournier, Turin, 25 January 1736 – Paris, 10 April 1813; also reported as Giuseppe Luigi Lagrange or Lagrangia) was an Italian Enlightenment Era mathematician and astronomer.
The Journal of Astronomical History and Heritage is a peer-reviewed academic journal.
Jupiter is the fifth planet from the Sun and the largest in the Solar System.
The is a neutrino and gravitational waves laboratory located underground in the Mozumi Mine of the Kamioka Mining and Smelting Co. near the Kamioka section of the city of Hida in Gifu Prefecture, Japan.
Karl Guthe Jansky (October 22, 1905 – February 14, 1950) was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way.
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 Kuiper belt, occasionally called the Edgeworth–Kuiper belt, is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun.
The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains a cosmological constant, denoted by Lambda (Greek Λ), associated with dark energy, and cold dark matter (abbreviated CDM).
Leonhard Euler (Swiss Standard German:; German Standard German:; 15 April 170718 September 1783) was a Swiss mathematician, physicist, astronomer, logician and engineer, who made important and influential discoveries in many branches of mathematics, such as infinitesimal calculus and graph theory, while also making pioneering contributions to several branches such as topology and analytic number theory.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool.
The LIGO Scientific Collaboration (LSC) is a scientific collaboration of international physics institutes and research groups dedicated to the search for gravitational waves.
The Linda Hall Library is a privately endowed American library of science, engineering and technology located in Kansas City, Missouri, sitting "majestically on a urban arboretum." It is the "largest independently funded public library of science, engineering and technology in North America" and "among the largest science libraries in the world.".
This is a list of traditional Arabic names for stars.
Astronomical instruments include.
This is a compilation of initialisms and acronyms commonly used in astronomy.
This list of Russian astronomers and astrophysicists includes the famous astronomers, astrophysicists and cosmologists from the Russian Empire, the Soviet Union and the Russian Federation.
The Little Ice Age (LIA) was a period of cooling that occurred after the Medieval Warm Period.
The Local Group is the galaxy group that includes the Milky Way.
A lunar eclipse occurs when the Moon passes directly behind Earth and into its shadow.
A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.
A magnetosphere is the region of space surrounding an astronomical object in which charged particles are manipulated or affected by that object's magnetic field.
In astronomy, the main sequence is a continuous and distinctive band of stars that appear on plots of stellar color versus brightness.
Maragheh observatory (رصدخانه مراغه), was an institutionalized astronomical observatory which was established in 1259 CE under the patronage of the Ilkhanid Hulagu and the directorship of Nasir al-Din al-Tusi, a Persian scientist and astronomer.
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.
A mathematical model is a description of a system using mathematical concepts and language.
Mathematics (from Greek μάθημα máthēma, "knowledge, study, learning") is the study of such topics as quantity, structure, space, and change.
In the classical physics observed in everyday life, matter is any substance that has mass and takes up space by having volume.
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.
The Maya civilization was a Mesoamerican civilization developed by the Maya peoples, and noted for its hieroglyphic script—the only known fully developed writing system of the pre-Columbian Americas—as well as for its art, architecture, mathematics, calendar, and astronomical system.
Mercury is the smallest and innermost planet in the Solar System.
In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.
A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky.
In the history of Europe, the Middle Ages (or Medieval Period) lasted from the 5th to the 15th century.
The Milky Way is the galaxy that contains our Solar System.
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).
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
Multi-messenger astronomy is astronomy based on the coordinated observation and interpretation of disparate "messenger" signals.
The terms Muslim world and Islamic world commonly refer to the unified Islamic community (Ummah), consisting of all those who adhere to the religion of Islam, or to societies where Islam is practiced.
The nanometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (m).
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.
A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body).
Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on empirical evidence from observation and experimentation.
A near-Earth object (NEO) is any small Solar System body whose orbit can bring it into proximity with Earth.
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.
Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories.
A neutrino detector is a physics apparatus which is designed to study neutrinos.
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
Abbé Nicolas-Louis de Lacaille, formerly sometimes spelled de la Caille, (15 March 1713 – 21 March 1762) was a French astronomer.
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.
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.
In theoretical astrophysics, the Nordtvedt effect refers to the relative motion between the Earth and the Moon which would be observed if the gravitational self-energy of a body contributed differently to its gravitational mass than to its inertial mass.
Nubians are an ethnolinguistic group indigenous to present-day Sudan and southern Egypt who originate from the early inhabitants of the central Nile valley, believed to be one of the earliest cradles of civilization.
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).
Nucleocosmochronology or nuclear cosmochronology is a technique used to determine timescales for astrophysical objects and events.
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.
Numerical analysis is the study of algorithms that use numerical approximation (as opposed to general symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics).
OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations.
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.
Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical models.
An observatory is a location used for observing terrestrial or celestial events.
On the Sizes and Distances (of the Sun and Moon) (Περὶ μεγεθῶν καὶ ἀποστημάτων, Peri megethon kai apostematon) is widely accepted as the only extant work written by Aristarchus of Samos, an ancient Greek astronomer who lived circa 310–230 BCE.
The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO) is an array of radio telescopes (2 fixed and 1 moveable, fully steerable 60-ft-diameter parabolic reflectors operating simultaneously at 1407 MHz and 408 MHz), Monthly Notices of the Royal Astronomical Society, Vol.
The Oort cloud, named after the Dutch astronomer Jan Oort, sometimes called the Öpik–Oort cloud, is a theoretical cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from.
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.
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.
The following outline is provided as an overview of and topical guide to space science: Space science encompasses all of the scientific disciplines that involve space exploration and study natural phenomena and physical bodies occurring in outer space, such as space medicine and astrobiology.
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.
Perturbation theory comprises mathematical methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem.
Phase is the position of a point in time (an instant) on a waveform cycle.
A phenomenon (Greek: φαινόμενον, phainómenon, from the verb phainein, to show, shine, appear, to be manifest or manifest itself, plural phenomena) is any thing which manifests itself.
Philosophical Transactions, titled Philosophical Transactions of the Royal Society (often abbreviated as Phil. Trans.) from 1776, is a scientific journal published by the Royal Society.
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.
Physical cosmology is the study of the largest-scale structures and dynamics of the Universe and is concerned with fundamental questions about its origin, structure, evolution, and ultimate fate.
Physical Review Letters (PRL), established in 1958, is a peer-reviewed, scientific journal that is published 52 times per year by the American Physical Society.
Physics (from knowledge of nature, from φύσις phýsis "nature") is the natural science that studies matterAt the start of The Feynman Lectures on Physics, Richard Feynman offers the atomic hypothesis as the single most prolific scientific concept: "If, in some cataclysm, all scientific knowledge were to be destroyed one sentence what statement would contain the most information in the fewest words? I believe it is that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another..." and its motion and behavior through space and time and that studies the related entities of energy and force."Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves."Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of the human intellect in its quest to understand our world and ourselves."Physics is an experimental science. Physicists observe the phenomena of nature and try to find patterns that relate these phenomena.""Physics is the study of your world and the world and universe around you." Physics is one of the oldest academic disciplines and, through its inclusion of astronomy, perhaps the oldest. Over the last two millennia, physics, chemistry, biology, and certain branches of mathematics were a part of natural philosophy, but during the scientific revolution in the 17th century, these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy. Advances in physics often enable advances in new technologies. For example, advances in the understanding of electromagnetism and nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus.
Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) was a French scholar whose work was important to the development of mathematics, statistics, physics and astronomy.
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.
In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center, while less dense materials rise to the surface, generally in a magma ocean.
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.
Pre-stellar cores are the nurseries of new stars, and are an early phase in the formation of low-mass stars, before gravitational collapse produces a central protostar.
Precession is a change in the orientation of the rotational axis of a rotating body.
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.
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.
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.
In quantum physics, a quantum fluctuation (or vacuum state fluctuation or vacuum fluctuation) is the temporary change in the amount of energy in a point in space, as explained in Werner Heisenberg's uncertainty principle.
A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).
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.
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 is the technology of using radio waves to carry information, such as sound, by systematically modulating properties of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width.
Radio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths, with luminosities up to 1039 W between 10 MHz and 100 GHz.
A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.
Randomness is the lack of pattern or predictability in events.
The Realencyclopädie der classischen Altertumswissenschaft, commonly called the Pauly–Wissowa or simply RE, is a German encyclopedia of classical scholarship.
Recorded history or written history is a historical narrative based on a written record or other documented communication.
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.
A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image.
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".
The Renaissance is a period in European history, covering the span between the 14th and 17th centuries.
A rocket (from Italian rocchetto "bobbin") is a missile, spacecraft, aircraft or other vehicle that obtains thrust from a rocket engine.
SAGE (Soviet–American Gallium Experiment, or sometimes Russian-American Gallium Experiment) is a collaborative experiment devised by several prominent physicists to measure the solar neutrino flux.
The Saros is a period of approximately 223 synodic months (approximately 6585.3211 days, or 18 years, 11 days, 8 hours), that can be used to predict eclipses of the Sun and Moon.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars.
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 1987A was a peculiar type II supernova in the Large Magellanic Cloud, a dwarf galaxy satellite of the Milky Way.
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).
The Solar SystemCapitalization of the name varies.
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona.
Space exploration is the discovery and exploration of celestial structures in outer space by means of evolving and growing space technology.
A space telescope or space observatory is an instrument located in outer space to observe distant planets, galaxies and other astronomical objects.
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.
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.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
Star clusters are groups of stars.
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.
In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
A stellar collision is the coming together of two stars caused by gravity, gravitational radiation, or other mechanisms not well understood.
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.
Stellar parallax is the apparent shift of position of any nearby star (or other object) against the background of distant objects.
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.
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings.
Sub-Saharan Africa is, geographically, the area of the continent of Africa that lies south of the Sahara.
The Sun is the star at the center of the Solar System.
A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos.
A supermassive black hole (SMBH or SBH) is the largest type of black hole, on the order of hundreds of thousands to billions of solar masses, and is found in the centre of almost all currently known massive galaxies.
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.
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova.
Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when charged particles are accelerated radially, i.e., when they are subject to an acceleration perpendicular to their velocity.
Temperature is a physical quantity expressing hot and cold.
A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals.
(ثابت بن قره, Thebit/Thebith/Tebit; 826 – February 18, 901) was a Syrian Arab Sabian mathematician, physician, astronomer, and translator who lived in Baghdad in the second half of the ninth century during the time of Abbasid Caliphate.
The Astronomical Journal (often abbreviated AJ in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society and currently published by IOP Publishing.
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.
Theoretical astronomy is the use of the analytical models of physics and chemistry to describe astronomical objects and astronomical phenomena.
Thorium is a weakly radioactive metallic chemical element with symbol Th and atomic number 90.
In physics and classical mechanics, the three-body problem is the problem of taking an initial set of data that specifies the positions, masses, and velocities of three bodies for some particular point in time and then determining the motions of the three bodies, in accordance with Newton's laws of motion and of universal gravitation, which are the laws of classical mechanics.
Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon), and the primary planet that it orbits (e.g. Earth).
Timbuktu, also spelt Tinbuktu, Timbuctoo and Timbuktoo (Tombouctou; Koyra Chiini: Tumbutu), is an ancient city in Mali, situated north of the Niger River.
The ultimate fate of the universe is a topic in physical cosmology, whose theoretical restrictions allow possible scenarios for the evolution and ultimate fate of the universe to be described and evaluated.
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray particle with a kinetic energy greater than eV, far beyond both the rest mass and energies typical of other cosmic ray particles.
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.
The Ulugh Beg Observatory is an observatory in Samarkand, Uzbekistan.
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
Universe: The Infinite Frontier was a 26 episode television series explaining all the stars and planets and having a look at the entire universe.
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public research university in Berkeley, California.
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.
The University of Virginia (U.Va. or UVA), frequently referred to simply as Virginia, is a public research university and the flagship for the Commonwealth of Virginia.
Uranium is a chemical element with symbol U and atomic number 92.
Uranus is the seventh planet from the Sun.
A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetic field.
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
Cosmic voids are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies.
Volcanism is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent.
In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport.
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.
Wide-field Infrared Survey Explorer (WISE) is a NASA infrared-wavelength astronomical space telescope launched in December 2009, and placed in hibernation in February 2011.
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.
The Wolf number (also known as the International sunspot number, relative sunspot number, or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the sun.
X-rays make up X-radiation, a form of electromagnetic radiation.
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects.
An X-ray astronomy satellite studies X-ray emissions from celestial objects, as part of a branch of space science known as X-ray astronomy.
X-ray binaries are a class of binary stars that are luminous in X-rays.
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.