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Astronomy: Aurora Borealis
Aurora Borealis An aurora (pl. aurorae or auroras) is a natural light display in Earth’s upper atmosphere caused by charged particles from the Sun colliding wi...
Astronomy: Callisto
Callisto Callisto ( kə-LIST-oh) is the second-largest moon of Jupiter, after Ganymede. It is also the third-largest moon in the Solar System, following Ganymed...
Astronomy: Ceres
Ceres Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the main asteroid belt between the orbits of Mars and Jupiter. It was the first known aste...
Astronomy: Charon
Charon Charon ( KAIR-on, -ən or SHARR-ən), formal designation (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto...
Astronomy: Chicxulub Impact
Chicxulub Impact The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named af...
Astronomy: Comet Hale-Bopp
Comet Hale-Bopp Comet Hale–Bopp (formally designated C/1995 O1) is a long-period comet that was one of the most widely observed of the 20th century and one of ...
Astronomy: Comet NEOWISE
Comet NEOWISE C/2020 F3 (NEOWISE) or Comet NEOWISE is a long period comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers during the N...
Astronomy: Deimos
Deimos Deimos () is the smaller and outer of the two natural satellites of Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes ...
Astronomy: Earth
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is made possible by Earth being an ocean world, the on...
Astronomy: Enceladus
Enceladus Enceladus is the sixth-largest moon of Saturn and the 18th largest in the Solar System. It is about 500 kilometres (310 miles) in diameter, about a t...
Astronomy: Eris
Eris Eris (minor-planet designation: 136199 Eris) is the most massive and second-largest known dwarf planet in the Solar System. It is a trans-Neptunian object...
Astronomy: Europa
Europa Europa ( ) is the smallest and least massive of Jupiter's four Galilean moons. It is observable from Earth with common binoculars and is a planetary-mas...
Astronomy: Ganymede
Ganymede Ganymede is a natural satellite of Jupiter and is the largest and most massive moon in the Solar System. Like Saturn's largest moon Titan, it is large...
Astronomy: Halley's Comet
Halley's Comet Halley's Comet is the only known short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, thoug...
Astronomy: Haumea
Haumea Haumea (minor-planet designation: 136108 Haumea) is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004 by a team headed by Mike Br...
Astronomy: Iapetus
Iapetus Iapetus () is the outermost of Saturn's large moons. With an estimated diameter of 1,469 km (913 mi), it is the third-largest moon of Saturn and the el...
Astronomy: Io
Io Io () is the innermost and second-smallest of the four Galilean moons of Jupiter. Slightly larger than Earth's Moon, Io is the fourth-largest natural satell...
Astronomy: Jupiter
Jupiter Jupiter is the fifth planet from the Sun, and the largest in the Solar System. It is a gas giant with a mass nearly 2.5 times that of all the other pla...
Astronomy: Lunar Eclipse
Lunar Eclipse A lunar eclipse, also called a blood moon, is an astronomical event that occurs when the Moon orbits through Earth's shadow. Lunar eclipses occ...
Astronomy: Makemake
Makemake Makemake (minor-planet designation: 136472 Makemake) is a dwarf planet in the Kuiper belt, a disk of icy bodies beyond the orbit of Neptune. It is the...
Astronomy: Mars
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance....
Astronomy: Mercury
Mercury Mercury is the first planet from the Sun and the smallest in the Solar System. It is a rocky planet with a trace atmosphere and a surface gravity sligh...
Astronomy: Meteor Showers
Meteor Showers 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. These ...
Astronomy: Mimas
Mimas Mimas is the seventh-largest natural satellite of Saturn. With a mean diameter of 396.4 kilometres or 246.3 miles, Mimas is the smallest astronomical bod...
Astronomy: Neptune
Neptune Neptune is the eighth and farthest known planet orbiting the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massi...
Astronomy: Perseid Meteor Shower
Perseid Meteor Shower The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle that are usually visible from mid-July to late-August. T...
Astronomy: Phobos
Phobos Phobos () is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American a...
Astronomy: Pluto
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-larges...
Astronomy: Saturn
Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 ...
Astronomy: Solar Eclipse
Solar Eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally ...
Astronomy: Solar Wind
Solar Wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of elec...
Astronomy: The Asteroid Belt
The Asteroid Belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the ...
Astronomy: The Kuiper Belt
The Kuiper Belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to app...
Astronomy: The Moon
The Moon The Moon is the only natural satellite of Earth. It orbits around Earth at an average distance of 384,399 kilometres (238,854 mi), a distance roughly ...
Astronomy: The Oort Cloud
The Oort Cloud The Oort cloud (pronounced ORT or OORT), sometimes called the Öpik–Oort cloud, is theorized to be a cloud of billions of icy planetesimals sur...
Astronomy: The Sun
The Sun The Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reaction...
Astronomy: The Tunguska Event
The Tunguska Event The Tunguska event was a large explosion of between three and 50 megatons TNT equivalent that occurred near the Podkamennaya Tunguska River ...
Astronomy: Titan
Titan Titan is the largest moon of Saturn and the second-largest in the Solar System. It is the only moon known to have a dense atmosphere—denser than Earth's—...
Astronomy: Triton
Triton Triton is the largest natural satellite of the planet Neptune. It is the only moon of Neptune massive enough to be rounded under its own gravity and hos...
Astronomy: Uranus
Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant....
Astronomy: Venus
Venus Venus is the second planet from the Sun. Similar in size and mass to Earth, Venus has no liquid water, and its atmosphere is far thicker and denser than ...
Astronomy: Aldebaran
Aldebaran Aldebaran (Arabic: الدَّبَرَان, lit. 'The Follower') is a star in the zodiac constellation of Taurus....
Astronomy: Alpha Centauri
Alpha Centauri Alpha Centauri (α Centauri, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus. It consists of three stars: Rigil ...
Astronomy: Antares
Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii....
Astronomy: Arcturus
Arcturus Arcturus is a red giant star in the northern constellation of Boötes, and the brightest star in the constellation. It has the Bayer designation α Boöt...
Astronomy: Betelgeuse
Betelgeuse Betelgeuse is a red supergiant star in the equatorial constellation of Orion. It is usually the tenth-brightest star in the night sky and, after Rig...
Astronomy: Binary Star Systems
Binary Star Systems A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars...
Astronomy: Black Holes
Black Holes A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of gen...
Astronomy: Brown Dwarfs
Brown Dwarfs Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. T...
Astronomy: Canopus
Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is designated α Carinae, which...
Astronomy: Capella
Capella Capella is the brightest star in the northern constellation of Auriga. It has the Bayer designation α Aurigae, which is Latinised to Alpha Aurigae and ...
Astronomy: Carina Nebula
Carina Nebula The Carina Nebula or Eta Carinae Nebula (catalogued as NGC 3372; also known as the Great Carina Nebula) is a large, complex area of bright and da...
Astronomy: Cat's Eye Nebula
Cat's Eye Nebula The Cat's Eye Nebula (also known as NGC 6543 and Caldwell 6) is a planetary nebula in the northern constellation of Draco, discovered by Willi...
Astronomy: Cepheid Variables
Cepheid Variables A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, ...
Astronomy: Crab Nebula
Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. The c...
Astronomy: Deneb
Deneb Deneb () is a blue supergiant star in the constellation of Cygnus. It is the brightest star in the constellation and the 19th brightest in the night sky,...
Astronomy: Eagle Nebula
Eagle Nebula The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611, and also known as the Star Queen Nebula) is a young open cluster of stars in t...
Astronomy: Helix Nebula
Helix Nebula The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludw...
Astronomy: Horsehead Nebula
Horsehead Nebula The Horsehead Nebula (also known as Barnard 33 or B33) is a small dark nebula located about 1,375 light-years (422 pc) from Earth in the const...
Astronomy: Lagoon Nebula
Lagoon Nebula The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant emission nebula with an H II region loc...
Astronomy: Magnetars
Magnetars A magnetar is a type of neutron star with an extremely powerful magnetic field (~109 to 1011 T, ~1013 to 1015 G). The magnetic-field decay (or dissip...
Astronomy: Main Sequence Stars
Main Sequence Stars In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and d...
Astronomy: Neutron Stars
Neutron Stars A neutron star is the gravitationally collapsed core of a massive supergiant star. It results from the supernova explosion of a massive star—comb...
Astronomy: Orion Nebula
Orion Nebula The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula in the Milky Way situated south of Orion's Belt in the constella...
Astronomy: Pillars of Creation
Pillars of Creation Pillars of Creation is a photograph taken by the Hubble Space Telescope that depicts elephant trunks of interstellar gas and dust in the Ea...
Astronomy: Planetary Nebulae
Planetary Nebulae A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in...
Astronomy: Polaris
Polaris Polaris is a yellow supergiant star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris (Latinized to Alpha Ursae...
Astronomy: Protostars
Protostars A protostar is a very young star that is still gathering mass from its parent molecular cloud. It is the earliest phase in the process of stellar ev...
Astronomy: Proxima Centauri
Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years (1.3 parsecs) away in the southern constellation of Cent...
Astronomy: Pulsars
Pulsars A pulsar (pulsating star, on the model of quasar) is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its...
Astronomy: Red Giant Stars
Red Giant Stars A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses (M☉)) in a late phase of stellar evolution. The ou...
Astronomy: Rigel
Rigel Rigel is a blue supergiant star in the equatorial constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and ...
Astronomy: Ring Nebula
Ring Nebula The Ring Nebula is a planetary nebula in the northern constellation of Lyra, about mid-way between the prominent stars Beta and Gamma Lyrae. It is ...
Astronomy: Sirius
Sirius Sirius is the brightest star in the night sky, located in the southern constellation of Canis Major. Its name is derived from the Greek word Σείριος (La...
Astronomy: Spica
Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, ...
Astronomy: Stellar Black Holes
Stellar Black Holes A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging ...
Astronomy: Stellar Evolution
Stellar Evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range f...
Astronomy: Stellar Nucleosynthesis
Stellar Nucleosynthesis In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleos...
Astronomy: Supernova 1987A
Supernova 1987A SN 1987A was a Type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately 51.4 kilop...
Astronomy: Supernovae
Supernovae A supernova (pl.: supernovae) is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive st...
Astronomy: Tarantula Nebula
Tarantula Nebula The Tarantula Nebula (also known as 30 Doradus) is a large H II region in the Large Magellanic Cloud (LMC), forming its south-east corner (fro...
Astronomy: The H-R Diagram
The H-R Diagram A Hertzsprung–Russell diagram (abbreviated as H–R diagram, HR diagram or HRD) is a scatter plot of stars showing the relationship between the s...
Astronomy: Variable Stars
Variable Stars A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be c...
Astronomy: Vega
Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated ...
Astronomy: White Dwarf Stars
White Dwarf Stars A white dwarf is a very dense type of star: in an Earth-sized volume, it packs a mass that is comparable to the Sun. A white dwarf radiates l...
Astronomy: 47 Tucanae
47 Tucanae 47 Tucanae or 47 Tuc (also designated as NGC 104 and Caldwell 106) is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.0...
Astronomy: Active Galactic Nuclei
Active Galactic Nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the elec...
Astronomy: Andromeda Galaxy
Andromeda Galaxy The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula ...
Astronomy: Antennae Galaxies
Antennae Galaxies The Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/Caldwell 61) are a pair of interacting galaxies in the constellation Co...
Astronomy: Barred Spiral Galaxies
Barred Spiral Galaxies A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of a...
Astronomy: Blazars
Blazars A blazar (neologism of "BL Lacertae" and "Quasar") is an active galactic nucleus (AGN) with a relativistic jet – a jet composed of ionized matter trave...
Astronomy: Cartwheel Galaxy
Cartwheel Galaxy The Cartwheel Galaxy (catalogue ESO 350-40 and PGC 2248) is a lenticular ring galaxy about 500 million light-years away in the constellation S...
Astronomy: Centaurus A
Centaurus A Centaurus A (also known as NGC 5128 or Caldwell 77) is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer...
Astronomy: Cigar Galaxy
Cigar Galaxy Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa...
Astronomy: Coma Cluster
Coma Cluster The Coma Cluster (Abell 1656) is a large cluster of galaxies that contains over 1,000 identified galaxies. Along with the Leo Cluster (Abell 1367)...
Astronomy: Dark Matter Halos
Dark Matter Halos In modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has de...
Astronomy: Elliptical Galaxies
Elliptical Galaxies An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of th...
Astronomy: Galaxy Clusters
Galaxy Clusters A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound toge...
Astronomy: Galaxy Mergers
Galaxy Mergers Interacting galaxies, also known as colliding galaxies, are two or more galaxies whose gravitational fields result in a disturbance of one anoth...
Astronomy: Globular Clusters
Globular Clusters A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards it...
Astronomy: Irregular Galaxies
Irregular Galaxies Irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not...
Astronomy: Large Magellanic Cloud
Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (163,00...
Astronomy: Messier 87
Messier 87 Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy in the constellation Virgo that conta...
Astronomy: NGC 1300
NGC 1300 NGC 1300 is a barred spiral galaxy located about 69 million light-years away in the constellation Eridanus. The galaxy is about 130,000 light-years ac...
Astronomy: Omega Centauri
Omega Centauri Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stel...
Astronomy: Open Clusters
Open Clusters An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roug...
Astronomy: Pinwheel Galaxy
Pinwheel Galaxy The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on, counterclockwise intermediate spiral galaxy located 21 million ...
Astronomy: Quasars
Quasars A quasar ( KWAY-zar) is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO....
Astronomy: Sagittarius A*
Sagittarius A* A* or A star may refer to: A* search algorithm, a pathfinding algorithm used in computing A*, the highest grade in some examination systems suc...
Astronomy: Small Magellanic Cloud
Small Magellanic Cloud The Small Magellanic Cloud (SMC) is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophot...
Astronomy: Sombrero Galaxy
Sombrero Galaxy The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a peculiar galaxy of unclear classification in the constellation bo...
Astronomy: Spiral Galaxies
Spiral Galaxies Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part o...
Astronomy: The Local Group
The Local Group The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It consists of two collections of galaxies in a "dumbb...
Astronomy: The Milky Way
The Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a ha...
Astronomy: The Pleiades
The Pleiades The Pleiades ( PLEE-ə-deez, PLAY-, PLY-), also known as Seven Sisters and Messier 45 (M45), is an asterism of an open star cluster containing youn...
Astronomy: Triangulum Galaxy
Triangulum Galaxy The Triangulum Galaxy is a spiral galaxy 2.878 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Mess...
Astronomy: Virgo Cluster
Virgo Cluster The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the Virgo constellation. Comprising approximat...
Astronomy: Whirlpool Galaxy
Whirlpool Galaxy The Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galac...
Astronomy: Big Bang Nucleosynthesis
Big Bang Nucleosynthesis In physical cosmology, Big Bang nucleosynthesis (also known as primordial nucleosynthesis, and abbreviated as BBN) is a model for the ...
Astronomy: Cosmic Inflation
Cosmic Inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very ...
Astronomy: Cosmic Microwave Background
Cosmic Microwave Background The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable univ...
Astronomy: Cosmic Strings
Cosmic Strings Cosmic strings are hypothetical 1-dimensional topological defects which may have formed during a symmetry-breaking phase transition in the early...
Astronomy: Cosmic Voids
Cosmic Voids Cosmic voids (also known as dark space) are vast spaces between filaments (the largest-scale structures in the universe), which contain very few o...
Astronomy: Dark Energy
Dark Energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on its largest scales. Its primary effect i...
Astronomy: Dark Matter
Dark Matter In astronomy and cosmology, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic ...
Astronomy: Gravitational Lensing
Gravitational Lensing A gravitational lens is matter, such as a cluster of galaxies or a point particle, that bends light from a distant source as it travels t...
Astronomy: Gravitational Waves
Gravitational Waves Gravitational waves are waves of spacetime curvature that propagate at the speed of light and are produced by the relative motion of gravit...
Astronomy: Heat Death of the Universe
Heat Death of the Universe The heat death of the universe (also known as the Big Chill or the Big Freeze) is a scientific hypothesis regarding the ultimate fat...
Astronomy: Large-Scale Structure
Large-Scale Structure The observable universe is a spherical region of the universe consisting of all matter that can be observed from Earth; the electromagnet...
Astronomy: Olbers' Paradox
Olbers' Paradox Olbers' paradox, also known as the dark night paradox or Olbers and Cheseaux's paradox, is a historical argument in astrophysics and physical ...
Astronomy: Redshift
Redshift In physics, a redshift is an increase in the wavelength, or equivalently, a decrease in the frequency, of electromagnetic radiation (such as light). T...
Astronomy: The Big Bang
The Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmolog...
Astronomy: The Big Crunch
The Big Crunch The Big Crunch is a hypothetical scenario for the ultimate fate of the universe, in which the expansion of the universe eventually reverses and ...
Astronomy: The Cosmic Web
The Cosmic Web The observable universe is a spherical region of the universe consisting of all matter that can be observed from Earth; the electromagnetic radi...
Astronomy: The Drake Equation
The Drake Equation The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Mi...
Astronomy: The Expanding Universe
The Expanding Universe The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It...
Astronomy: The Fermi Paradox
The Fermi Paradox The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likeli...
Astronomy: The Great Attractor
The Great Attractor The Great Attractor is a region of gravitational attraction in intergalactic space and the apparent central gravitational point of the Lani...
Astronomy: The Hubble Constant
The Hubble Constant Hubble's law, officially the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at spee...
Astronomy: The Multiverse Theory
The Multiverse Theory The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the e...
Astronomy: The Observable Universe
The Observable Universe The observable universe is a spherical region of the universe consisting of all matter that can be observed from Earth; the electromagn...
Astronomy: ALMA
ALMA The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, ...
Astronomy: Apollo 11
Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon, and the fifth crewed mission of NASA's Apollo program...
Astronomy: Apollo 13
Apollo 13 Apollo 13 (April 11–17, 1970) was the seventh crewed mission in the Apollo space program and would have been the third Moon landing. The craft was la...
Astronomy: Arecibo Observatory
Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Obs...
Astronomy: Artemis Program
Artemis Program The Artemis program is a Moon exploration program led by the United States' National Aeronautics and Space Administration (NASA), aimed at retu...
Astronomy: Cassini-Huygens
Cassini-Huygens Cassini–Huygens ( kə-SEE-nee HOY-gənz), commonly called Cassini, was a joint space-research mission by NASA, the European Space Agency (ESA), a...
Astronomy: Chandra X-ray Observatory
Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space t...
Astronomy: Curiosity Rover
Curiosity Rover Curiosity is a Mars rover that is exploring Gale crater and Mount Sharp on Mars as part of NASA's Mars Science Laboratory (MSL) mission. Launch...
Astronomy: Dawn Mission
Dawn Mission Dawn is a retired space probe that was launched by NASA in September 2007 with the mission of studying two of the three known protoplanets of the ...
Astronomy: Event Horizon Telescope
Event Horizon Telescope The Event Horizon Telescope (EHT) is a telescope array consisting of a global network of radio telescopes. The EHT project combines dat...
Astronomy: Gemini Program
Gemini Program Project Gemini (IPA: ) was the second United States human spaceflight program to fly. It was conducted after the first American crewed space pro...
Astronomy: Hubble Space Telescope
Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation....
Astronomy: Ingenuity Helicopter
Ingenuity Helicopter Ingenuity, nicknamed Ginny, is an autonomous NASA helicopter that operated on Mars from 2021 to 2024 as part of the Mars 2020 mission. Ing...
Astronomy: International Space Station
International Space Station The International Space Station (ISS) is a space station in low Earth orbit (LEO). It is the product of the International Space Sta...
Astronomy: James Webb Space Telescope
James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. It is the largest telescope in sp...
Astronomy: Juno Mission
Juno Mission Juno is a NASA space probe orbiting the planet Jupiter. Built by Lockheed Martin and operated by NASA's Jet Propulsion Laboratory, the spacecraft ...
Astronomy: Kepler Space Telescope
Kepler Space Telescope The Kepler space telescope is an inactive space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars....
Astronomy: LIGO
LIGO The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational...
Astronomy: Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter The Mars Reconnaissance Orbiter (MRO) is a spacecraft designed to search for the existence of water on Mars and provide support for...
Astronomy: New Horizons
New Horizons New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. It was launched in 2006, becoming the first spac...
Astronomy: Parker Solar Probe
Parker Solar Probe The Parker Solar Probe (PSP; previously Solar Probe, Solar Probe Plus or Solar Probe+) is a NASA space probe launched in 2018 to make observ...
Astronomy: Perseverance Rover
Perseverance Rover Perseverance is a NASA rover that has been exploring Mars since February 18, 2021, as part of the Mars 2020 mission. Built and managed by th...
Astronomy: Rosetta Mission
Rosetta Mission Rosetta was a space probe built by the European Space Agency that launched on 2 March 2004. Along with Philae, its lander module, Rosetta perfo...
Astronomy: SOHO
SOHO The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi S...
Astronomy: Skylab
Skylab Skylab was the United States' first space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by ...
Astronomy: Space Shuttle Program
Space Shuttle Program The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration ...
Astronomy: SpaceX Crew Dragon
SpaceX Crew Dragon Dragon 2 is a class of partially reusable spacecraft developed, manufactured, and operated by the American space company SpaceX for flights ...
Astronomy: Spitzer Space Telescope
Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope that was active be...
Astronomy: Sputnik 1
Sputnik 1 Sputnik 1 (, Russian: Спутник-1, Satellite 1), often referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into a...
Astronomy: TESS
TESS Transiting Exoplanet Survey Satellite (TESS) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method ...
Astronomy: Very Large Telescope
Very Large Telescope The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Para...
Astronomy: Vostok 1
Vostok 1 Vostok 1 (Russian: Восток, lit. 'East' or 'Orient') was the first spaceflight of the Vostok programme and the first human orbital spaceflight in hist...
Astronomy: Voyager 1
Voyager 1 Voyager 1 is a space probe launched by NASA on September 5, 1977, as part of the Voyager program, to study the outer Solar System and the interstella...
Astronomy: Voyager 2
Voyager 2 Voyager 2 is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory towards the gas gia...
Astronomy: Annie Jump Cannon
Annie Jump Cannon Annie Jump Cannon (; December 11, 1863 – April 13, 1941) was an American astronomer whose cataloging work was instrumental in the development...
Astronomy: Carl Sagan
Carl Sagan Carl Edward Sagan (; SAY-gən; November 9, 1934 – December 20, 1996) was an American astronomer, planetary scientist and science communicator. Initia...
Astronomy: Caroline Herschel
Caroline Herschel Caroline Lucretia Herschel ( HUR-shəl, HAIR-shəl, German: [kaʁoˈliːnə ˈhɛʁʃl̩]; 16 March 1750 – 9 January 1848) was a German astronomer, whos...
Astronomy: Cecilia Payne-Gaposchkin
Cecilia Payne-Gaposchkin Cecilia Payne-Gaposchkin (born Cecilia Helena Payne; (1900-05-10)May 10, 1900 – (1979-12-07)December 7, 1979) was a British-born Ameri...
Astronomy: Charles Messier
Charles Messier Charles Messier (French: [ʃaʁl me.sje]; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consistin...
Astronomy: Clyde Tombaugh
Clyde Tombaugh Clyde William Tombaugh (; February 4, 1906 – January 17, 1997) was an American astronomer and telescope maker, best known for discovering Pluto ...
Astronomy: Edmund Halley
Edmund Halley Edmond (or Edmund) Halley (; 8 November [O.S. 29 October] 1656 – 25 January 1742 [O.S....
Astronomy: Edwin Hubble
Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of ex...
Astronomy: Fritz Zwicky
Fritz Zwicky Fritz Zwicky (; German: [ˈtsvɪki]; February 14, 1898 – February 8, 1974) was a Swiss astronomer. He worked most of his life at the California Inst...
Astronomy: Galileo Galilei
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei, was an Italian astronome...
Astronomy: Georges Lemaitre
Georges Lemaitre Georges Henri Joseph Édouard Lemaître ( lə-MET-rə; French: [ʒɔʁʒ ləmɛːtʁ] ; 17 July 1894 – 20 June 1966) was a Belgian Catholic priest, theore...
Astronomy: Gerard Kuiper
Gerard Kuiper Gerard Peter Kuiper ( KY-pər; born Gerrit Pieter Kuiper, Dutch: [ˈɣɛrɪt ˈpitər ˈkœypər]; 7 December 1905 – 23 December 1973) was a Dutch astronom...
Astronomy: Harlow Shapley
Harlow Shapley Harlow Shapley (November 2, 1885 – October 20, 1972) was an American astronomer, who served as head of the Harvard College Observatory from 1921...
Astronomy: Henrietta Leavitt
Henrietta Leavitt Henrietta Swan Leavitt (; July 4, 1868 – December 12, 1921) was an American astronomer. Her discovery of how to effectively measure vast astr...
Astronomy: Isaac Newton & Gravity
Isaac Newton & Gravity Sir Isaac Newton ( ; 4 January [O.S. 25 December] 1643 – 31 March [O.S....
Astronomy: Jan Oort
Jan Oort Jan Hendrik Oort ( or ; 28 April 1900 – 5 November 1992) was a Dutch astronomer who made significant contributions to the understanding of the Milky ...
Astronomy: Jocelyn Bell Burnell
Jocelyn Bell Burnell Dame Susan Jocelyn Bell Burnell (; née Bell; born 15 July 1943) is a Northern Irish physicist who, while conducting research for her docto...
Astronomy: Johannes Kepler
Johannes Kepler Johannes Kepler (27 December 1571 – 15 November 1630) was a German polymath who was an astronomer, mathematician, astrologer, natural philosoph...
Astronomy: Karl Schwarzschild
Karl Schwarzschild Karl Schwarzschild (German: [kaʁl ˈʃvaʁtsʃɪlt] ; 9 October 1873 – 11 May 1916) was a German physicist and astronomer. Schwarzschild provided...
Astronomy: Nicolaus Copernicus
Nicolaus Copernicus Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Renaissance polymath who formulated a model of the universe that placed the Sun ...
Astronomy: Percival Lowell
Percival Lowell Percival Lowell (; March 13, 1855 – November 12, 1916) was an American businessman, author, mathematician, and astronomer who fueled speculatio...
Astronomy: Stephen Hawking
Stephen Hawking Stephen William Hawking (8 January 1942 – 14 March 2018) was an English theoretical astrophysicist, cosmologist, and author who was director of...
Astronomy: Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar Subrahmanyan Chandrasekhar ( CHƏN-drə-SHAY-kər; Tamil: சுப்பிரமணியன் சந்திரசேகர், romanized: Cuppiramaṇiyaṉ Cantiracēkar; 19 October...
Astronomy: Tycho Brahe
Tycho Brahe Tycho Brahe ( TY-koh BRAH-(h)ee, - BRAH(-hə); Danish: [ˈtsʰykʰo ˈpʁɑːə] ; born Tyge Ottesen Brahe, Danish: [ˈtsʰyːjə ˈʌtəsn̩ ˈpʁɑːə]; 14 December ...
Astronomy: Vera Rubin
Vera Rubin Vera Florence Cooper Rubin (; July 23, 1928 – December 25, 2016) was an American astronomer who pioneered work on galaxy rotation rates. She uncover...
Astronomy: William Herschel
William Herschel Frederick William Herschel ( HUR-shəl; German: Friedrich Wilhelm Herschel [ˈfʁiːdʁɪç ˈvɪlhɛlm ˈhɛʁʃl̩]; 15 November 1738 – 25 August 1822) wa...
Astronomy: Absolute Magnitude
Absolute Magnitude In astronomy, absolute magnitude (M) is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude s...
Astronomy: Accretion Disks
Accretion Disks An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The c...
Astronomy: Apparent Magnitude
Apparent Magnitude Apparent magnitude (m) is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. ...
Astronomy: Constellations
Constellations A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representin...
Astronomy: Coronal Mass Ejections
Coronal Mass Ejections A coronal mass ejection (CME) is a significant ejection of plasma mass from the Sun's corona into the heliosphere. CMEs are often associ...
Astronomy: Cosmic Rays
Cosmic Rays Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move thro...
Astronomy: Doppler Effect
Doppler Effect The Doppler effect (also Doppler shift) is the change in the frequency or, equivalently, the period of a wave in relation to an observer who is ...
Astronomy: Electromagnetic Spectrum
Electromagnetic Spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is div...
Astronomy: Event Horizons
Event Horizons In astrophysics, an event horizon is a boundary in spacetime beyond which no signal can ever reach a given observer. Wolfgang Rindler coined the...
Astronomy: Exoplanets
Exoplanets An exoplanet or extrasolar planet is a planet outside of the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar...
Astronomy: Hawking Radiation
Hawking Radiation Hawking radiation is black-body radiation released outside a black hole's event horizon due to quantum effects according to a model developed...
Astronomy: Kepler's Laws of Motion
Kepler's Laws of Motion In astronomy, Kepler's laws of planetary motion give good approximations for the orbits of planets around the Sun. They were published ...
Astronomy: Kepler-442b
Kepler-442b Kepler-442b (also known by its Kepler object of interest designation KOI-4742.01) is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting...
Astronomy: Lagrange Points
Lagrange Points In celestial mechanics, the Lagrange points (), also called the Lagrangian points or libration points, are points of equilibrium for small-mass...
Astronomy: Orion Constellation
Orion Constellation Orion is a prominent set of stars visible during winter in the northern celestial hemisphere. It is one of the 88 modern constellations; it...
Astronomy: Planetary Formation
Planetary Formation The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar Syst...
Astronomy: Planetary Rings
Planetary Rings A ring system is a disc or torus orbiting an astronomical object that is composed of numerous solid bodies such as dust particles, meteoroids, ...
Astronomy: Protoplanetary Disks
Protoplanetary Disks A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or He...
Astronomy: Proxima Centauri b
Proxima Centauri b Proxima Centauri b is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri in the constellation Centaurus....
Astronomy: Retrograde Motion
Retrograde Motion Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed ...
Astronomy: Schwarzschild Radius
Schwarzschild Radius The Schwarzschild radius is a parameter in the Schwarzschild solution to Einstein's field equations that corresponds to the radius of a sp...
Astronomy: Sidereal Time
Sidereal Time Sidereal time ("sidereal" pronounced sy-DEER-ee-əl, sə-) is a system of timekeeping used especially by astronomers. Using sidereal time and the ...
Astronomy: Solar Flares
Solar Flares A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and...
Astronomy: Southern Cross
Southern Cross Crux ( KRUKS) is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the South...
Astronomy: Space Weather
Space Weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its h...
Astronomy: Spectroscopy
Spectroscopy Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, inc...
Astronomy: Stellar Parallax
Stellar Parallax Stellar parallax is the apparent shift of position (parallax) of any nearby star (or other object) against the background of distant stars. By...
Astronomy: TRAPPIST-1 System
TRAPPIST-1 System TRAPPIST-1 also known as 2MASS J23062928−0502285 or SPECULOOS-1, is a red dwarf star with seven known planets. It lies in the constellation A...
Astronomy: The Astronomical Unit
The Astronomical Unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to 149597870700 m. Historically, the astronomica...
Astronomy: The Celestial Sphere
The Celestial Sphere In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. A...
Astronomy: The Ecliptic
The Ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. It was a central concept in a number of ancient sciences, providing t...
Astronomy: The Habitable Zone
The Habitable Zone In astronomy and astrobiology, the habitable zone (HZ), the circumstellar habitable zone (CHZ), the Goldilocks zone, is the range of orbits ...
Astronomy: The Light-Year
The Light-Year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly 9...
Astronomy: The Parsec
The Parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equa...
Astronomy: The Roche Limit
The Roche Limit In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, ...
Astronomy: The Zodiac
The Zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path o...
Astronomy: Tidal Forces
Tidal Forces The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field. It cause...
Astronomy: Tidal Locking
Tidal Locking Tidal locking between a pair of co-orbiting astronomical bodies occurs when one of the objects reaches a state where there is no longer any net c...
Astronomy: Trojan Asteroids
Trojan Asteroids The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit ...
Astronomy: Ursa Major
Ursa Major Ursa Major, also known as the Great Bear, is a constellation in the Northern Sky, whose associated mythology likely dates back into prehistory. Its ...