Browse All Content
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 with atoms in the atmosphere....
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 Ganymede and Saturn's moon Titan, and nearly as...
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 asteroid, discovered on 1 January 1801 by Gi...
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. It has a mean radius of 606 km (377 mi...
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 after the onshore community of Chicxulub P...
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 the brightest seen for many decades. Ala...
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 NEOWISE mission of the Wide-field Infrare...
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 30.3 hours to orbit Mars....
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 only one in the Solar System sustaining li...
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 tenth of that of Saturn's largest moon, 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 (TNO) in the scattered disk and has a h...
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-mass moon, slightly smaller and less massiv...
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 larger than the planet Mercury, but has somew...
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, though with the majority of recorded appariti...
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 Brown of Caltech at the Palomar Observator...
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 eleventh-largest in the Solar System....
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 satellite in the Solar System, has the highest...
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 planets in the Solar System combined and sl...
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 occur during eclipse season, when the Moon'...
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 fourth largest trans-Neptunian object a...
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 slightly higher than that of Mars....
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 meteors are caused by streams of cosmic ...
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 body known to be roughly rounded in shape d...
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-massive planet, and the densest giant planet....
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. The meteors are called the Perseids becau...
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 astronomer Asaph Hall....
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-largest and tenth-most-massive known object to...
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 times that of Earth....
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 or partially. Such an alignment occurs a...
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 electrons, protons and alpha particles with ...
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 planets Jupiter and Mars. It contains a ...
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 approximately 50 AU from the Sun. It is sim...
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 30 times the width of Earth....
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 surrounding the Sun at distances ranging fr...
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 reactions in its core, radiating the energy from...
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 in Yeniseysk Governorate (now Krasnoyars...
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—and is the only known object in the Sola...
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 hosts a thin, hazy atmosphere....
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 that of any other rocky body in the Sola...
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 Kentaurus (α Centauri A), Toliman (α Cen...
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 Boötis, which is Latinized to Alpha Boötis a...
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 Rigel, the second brightest in its constell...
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 are among the most important objects in...
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 general relativity, which describes gravita...
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. Their mass is approximately 13 to 80 time...
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 is romanized (transliterated) to Alpha ...
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 abbreviated Alpha Aur or α Aur....
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 dark nebulosity in the constellation Carin...
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 William Herschel on February 15, 1786. It was...
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, with a well-defined stable period (typic...
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 common name comes from a drawing that som...
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, with an apparent magnitude slightly var...
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 the constellation Serpens, discovered by ...
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 Ludwig Harding, most likely before 1824, thi...
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 constellation of Orion. The nebula is located...
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 located in the constellation Sagittarius. D...
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 dissipation) powers the emission of high-energ...
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 distinctive band. Stars spend the majorit...
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—combined with gravitational collapse—that co...
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 constellation of Orion, and is known as the middl...
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 Eagle Nebula of the Serpens constellation,...
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 their lives. The term "planetary nebula...
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 Minoris) and is commonly called the Nor...
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 evolution....
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 Centaurus. Discovered in 1915 by Robert Inne...
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 magnetic poles. This radiation can be o...
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 outer atmosphere is inflated and tenuous, ...
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 abbreviated Beta Ori or β Ori....
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 also catalogued as Messier 57, M57 and N...
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 (Latin script: Seirios; lit....
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, which is Latinised to Alpha Virginis and...
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 from about 5 to several tens of solar ma...
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 from a few million years for the most mas...
Astronomy: Stellar Nucleosynthesis
Stellar Nucleosynthesis In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original...
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 kiloparsecs (168,000 light-years) from Earth ...
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 star, or when a white dwarf is triggered i...
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 (from Earth's perspective)....
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 stars' absolute magnitudes or luminositie...
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 caused by a change in emitted light or by...
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 Alpha Lyr or α Lyr....
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 light from residual heat, not from nuclea...
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 ± 0.01 kpc (14,500 ± 32.6 ly) from Earth, and...
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 electromagnetic spectrum, with characteristi...
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 and is cataloged as Messier 31, M31, and...
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 Corvus. They are currently going through a...
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 all spiral galaxies in the local universe...
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 traveling at nearly the speed of light – dire...
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 Sculptor. It has a D25 isophotal diameter...
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 James Dunlop from his home in Parramatt...
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 Major. It is the second-largest member ...
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), it is one of the two major clusters co...
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 decoupled from cosmic expansion and contai...
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 the three main classes of galaxy described...
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 together by gravity, with typical masses ran...
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 another. There are several types of galactic ...
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 its center. It can contain anywhere from t...
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 fall into any of the regular classes of...
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 (163,000 light-years), the LMC is the second- o...
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 contains several trillion stars. One of the l...
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 across....
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-stellar object by Edmond Halley in 1677. Loc...
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 roughly the same age. More than 1,100 open c...
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 light-years (6.4 megaparsecs) from Earth...
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 such as the GCE Advanced Level A*STAR, the ...
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 isophotal diameter of about 5.78 kiloparsecs (1...
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 borders of Virgo and Corvus, being about 9...
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 of the Hubble sequence. Most spiral galax...
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 "dumbbell" shape; the Milky Way and its satell...
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 hazy band of light seen in the night sky f...
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 young B-type stars in the northwest of the c...
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 Messier 33 or NGC 598....
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 approximately 1,300 (and possibly up to 2,000) mem...
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 galactic nucleus. It lies in the constellatio...
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 production of light nuclei (including, b...
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 early universe. This enormous expansion ...
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 universe. With a standard optical telescope,...
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 universe when the topology of the vacuu...
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 or no galaxies. In spite of their size, m...
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 is to drive the accelerating expansion of...
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 radiation. Dark matter is implied by gra...
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 toward an observer. The amount of gravita...
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 gravitating masses. They were first predicted ...
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 fate of the universe which posits the unive...
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 electromagnetic radiation from these astronomical obj...
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 cosmology that says the darkness of the ...
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). The opposite change, a decrease in wavele...
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 cosmological models based on the Big Bang concep...
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 the universe recollapses, ultimately cau...
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 radiation from these astronomical objects ha...
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 Milky Way Galaxy. The equation was formula...
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 is an intrinsic expansion, so it does n...
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 likelihood of its existence. In simple terms, ...
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 Laniakea Supercluster of galaxies that inclu...
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 speeds proportional to their distance. In ot...
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 entirety of space, time, matter, energy, ...
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 electromagnetic radiation from these astronomical o...
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, which observe electromagnetic radiation ...
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. The mission was crewed by Commander Ne...
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 launched from Kennedy Space Center on Apri...
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 Observatory, is an observatory in Barrio Es...
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 returning humans to the Moon for the first t...
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), and the Italian Space Agency (ASI) to sen...
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 telescope launched aboard the Space Shutt...
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. Launched in 2011 and landed the following year...
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 asteroid belt: Vesta and Ceres. In the f...
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 data from several very-long-baseline interf...
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 program, Project Mercury, while the Apollo ...
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. It was not the first space telescope, b...
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. Ingenuity made its first flight on 19 April...
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 Station program and is operated by five par...
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 space, and is equipped with high-resolutio...
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 was launched from Cape Canaveral Air For...
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. Named after astronomer Johannes Kepler,...
Astronomy: LIGO
LIGO The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves. Prior to LIGO, all data about th...
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 missions to Mars, as part of NASA's Mar...
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 spacecraft to perform a flyby study of the P...
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 observations of the Sun's outer corona. It use...
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 the Jet Propulsion Laboratory, it was laun...
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 performed a detailed study of comet 67P/Chury...
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 Space (now Airbus Defence and Space) that...
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 three trios of astronaut crews: Skylab 2...
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 (NASA), which accomplished routine trans...
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 to the International Space Station (ISS)...
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 between 2003 and 2020. Spitzer was the thi...
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 an elliptical low Earth orbit by the Sovi...
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 in an area 400 times larger than that co...
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 Paranal in the Atacama Desert of northern Ch...
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 history....
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 interstellar space beyond the Sun's heliosphere. It...
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 giants (Jupiter and Saturn) and enabled fur...
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 of contemporary stellar classification....
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. Initially an assistant professor at Harvard, S...
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, whose most significant contributions to astr...
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 American astronomer and astrophysicist. Her w...
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 consisting of 110 nebulae and star clusters, whic...
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 in 1930, marking the first detection of ...
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 extragalactic astronomy and observational ...
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 Institute of Technology in the United States...
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 astronomer, physicist, and engineer, sometimes de...
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, theoretical physicist, and mathematician who m...
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 astronomer, planetary scientist, selenographer, ...
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 1921–1952, and political activist during the...
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 astronomical distances led to a shift in the...
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 Way and who was a pioneer in the field o...
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 doctorate, discovered the first radio pulsars...
Astronomy: Johannes Kepler
Johannes Kepler Johannes Kepler (27 December 1571 – 15 November 1630) was a German polymath who was an astronomer, mathematician, astrologer, natural philosopher and music theorist. He is a key figur...
Astronomy: Karl Schwarzschild
Karl Schwarzschild Karl Schwarzschild (German: [kaʁl ˈʃvaʁtsʃɪlt] ; 9 October 1873 – 11 May 1916) was a German physicist and astronomer. Schwarzschild provided the first exact solution to the Einstei...
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 rather than Earth at its center. The pub...
Astronomy: Percival Lowell
Percival Lowell Percival Lowell (; March 13, 1855 – November 12, 1916) was an American businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, and fu...
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 research at the Centre for Theoretical ...
Astronomy: Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar Subrahmanyan Chandrasekhar ( CHƏN-drə-SHAY-kər; Tamil: சுப்பிரமணியன் சந்திரசேகர், romanized: Cuppiramaṇiyaṉ Cantiracēkar; 19 October 1910 – 21 August 1995) was an Indian-Am...
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 1546 – 24 October 1601), generally calle...
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 uncovered the discrepancy between the predicted...
Astronomy: William Herschel
William Herschel Frederick William Herschel ( HUR-shəl; German: Friedrich Wilhelm Herschel [ˈfʁiːdʁɪç ˈvɪlhɛlm ˈhɛʁʃl̩]; 15 November 1738 – 25 August 1822) was a German-British astronomer and compos...
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 scale; the more luminous (intrinsically b...
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 central body is most frequently a star....
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. Its value depends on its intrinsic lumin...
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 representing an animal, mythological subject, or in...
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 associated with solar flares and other forms o...
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 through space at nearly the speed of light. ...
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 moving relative to the source of the wav...
Astronomy: Electromagnetic Spectrum
Electromagnetic Spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different...
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 term in the 1950s....
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, and the first detection around a main-...
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 by Stephen Hawking in 1974. The radiati...
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 by Johannes Kepler from 1608 to 1621 in ...
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 within the habitable zone of the K-type...
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 objects under the gravitational influen...
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 was among the 48 constellations listed ...
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 System (as well as other planetary systems)....
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, minor planets, moonlets, or stellar obje...
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 Herbig Ae/Be star. The protoplanetary disk...
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. It can also be referred to as Proxima b...
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 from a particular vantage point. Direct ...
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 sphere in flat space that has the same sur...
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 celestial coordinate system, it is easy ...
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 are often, but not always, accompanied ...
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 Southern Cross. It lies on the southern end o...
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 heliosphere. This includes the effects of...
Astronomy: Spectroscopy
Spectroscopy Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray...
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 extension, it is a method for determini...
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 Aquarius approximately 40.66 light-years ...
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 astronomical unit was conceived as the average Eart...
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. All objects in the sky can be conceived 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 the framework for key measurements in ast...
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 around a star within which a planetary s...
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 9460730472580.8 km, which is approximatel...
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 equal to 3.26 light-years or 206265 astronom...
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, held together only by its own force of g...
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 of the Sun across the celestial sphere ov...
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 causes different parts of bodies to be pulled...
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 change in its rotation rate over the cour...
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 around the Sun. Relative to Jupiter, eac...
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 Latin name means "greater (or larger) be...