159 relations: AB magnitude, Airglow, Almagest, Alpha Centauri, Andromeda Galaxy, Apsis, Arcturus, Aristotle, Astronomical object, Astronomical unit, Atmosphere of Earth, Betelgeuse, Binoculars, Black body, Bortle scale, Bright Star Catalogue, Brightness, Callirrhoe (moon), Canopus, Celestial sphere, Centaur (minor planet), Ceres (dwarf planet), Charge-coupled device, Charon (moon), Circumstellar disc, Comet Ikeya–Seki, Common logarithm, Conjunction (astronomy), Cosmic dust, Distance modulus, Double star, Earth, Epsilon Canis Majoris, Eris (dwarf planet), Eta Carinae, European Southern Observatory, Extinction (astronomy), Fenrir (moon), First magnitude star, Flux, Full moon, Full width at half maximum, Gamma-ray burst, Ganymede (moon), General relativity, GRB 080319B, Halley's Comet, Haumea, Hellenistic Greece, Hipparchus, ..., Historical brightest stars, Hubble Space Telescope, Human, Human eye, Hydra (moon), Iapetus (moon), Infrared, Infrared astronomy, Infrared excess, International Space Station, Inverse-square law, Irradiance, James Webb Space Telescope, Jansky, Jet Propulsion Laboratory, JPL Horizons On-Line Ephemeris System, Jupiter, K correction, Kreutz sungrazer, Kuiper belt, Large Magellanic Cloud, LBV 1806-20, Light-year, List of brightest stars, List of nearest bright stars, List of nearest stars and brown dwarfs, Logarithm, Logarithmic scale, Luminosity, Luminosity distance, Lux, Magnitude (astronomy), Makemake, Mars, Mercury (planet), Messier 41, Messier 81, Milky Way, Monochrome, Monthly Notices of the Royal Astronomical Society, Moon, N. R. Pogson, Naked eye, NASA, Neptune, New moon, Night sky, Nix (moon), Non-Euclidean geometry, Occultation, Opposition (planets), Opposition surge, Parsec, Passband, Perihelion and aphelion, Phase curve (astronomy), Photodetector, Photographic film, Photographic magnitude, Photometric system, Photometry (astronomy), Planck's law, Pluto, Polaris, Power law, Ptolemy, Quasar, Rayleigh scattering, Red dwarf, Red giant, Rigel, Ritchey–Chrétien telescope, Satellite flare, Saturn, Sirius, SN 1006, SN 1054, SN 1987A, Spectral energy distribution, Spectral flux density, Star, Stellar classification, Stevens's power law, Subaru Telescope, Sun, Supergiant star, Supernova impostor, Surface brightness, Telescope, The Astrophysical Journal, Titan (moon), Triangulum Galaxy, Triton (moon), UBV photometric system, Ultraviolet, Uranus, Vega, Venus, Visible spectrum, Visual perception, Weber–Fechner law, Zeta1 Scorpii, 10 Hygiea, 2 Pallas, 2060 Chiron, 3C 273, 4 Vesta, 7 Iris, 90377 Sedna. Expand index (109 more) » « Shrink index
The AB magnitude system is an astronomical magnitude system.
Airglow (also called nightglow) is a faint emission of light by a planetary atmosphere.
The Almagest is a 2nd-century Greek-language mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy. One of the most influential scientific texts of all time, its geocentric model was accepted for more than 1200 years from its origin in Hellenistic Alexandria, in the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until Copernicus.
Alpha Centauri (α Centauri, abbreviated Alf Cen or α Cen) is the star system closest to the Solar System, being from the Sun.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.
An apsis (ἁψίς; plural apsides, Greek: ἁψῖδες) is an extreme point in the orbit of an object.
Aristotle (Ἀριστοτέλης Aristotélēs,; 384–322 BC) was an ancient Greek philosopher and scientist born in the city of Stagira, Chalkidiki, in the north of Classical Greece.
An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.
The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
Betelgeuse, also designated Alpha Orionis (α Orionis, abbreviated Alpha Ori, α Ori), is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion.
Binoculars or field glasses are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
The Bortle scale is a nine-level numeric scale that measures the night sky's brightness of a particular location.
The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth.
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.
Callirrhoe (Greek: Καλλιρρόη), also known as (17), is one of Jupiter's outermost named natural satellites.
Canopus, also designated Alpha Carinae (α Carinae, abbreviated Alpha Car, α Car), is the brightest star in the southern constellation of Carina, and the second-brightest star in the night-time sky, after Sirius.
In astronomy and navigation, the celestial sphere is an abstract sphere with an arbitrarily large radius concentric to Earth.
Centaurs are small solar system bodies with a semi-major axis between those of the outer planets.
Ceres (minor-planet designation: 1 Ceres) is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter, slightly closer to Mars' orbit.
A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value.
Charon, also known as (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto.
Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.
The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.
Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.
Christmas traditions vary from country to country.
A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a star.
Comet Ikeya–Seki, formally designated C/1965 S1, 1965 VIII, and 1965f, was a long-period comet discovered independently by Kaoru Ikeya and Tsutomu Seki.
In mathematics, the common logarithm is the logarithm with base 10.
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.
Cosmic dust, also called extraterrestrial dust or space dust, is dust which exists in outer space, as well as all over planet Earth.
The distance modulus is a way of expressing distances that is often used in astronomy.
In observational astronomy, a double star or visual double is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
Epsilon Canis Majoris (ε Canis Majoris, abbreviated Epsilon CMa, ε CMa), also named Adhara, is a binary star and, despite being designated 'epsilon', the second-brightest star in the constellation of Canis Major and one of the brightest stars in the night sky.
Eris (minor-planet designation 136199 Eris) is the most massive and second-largest (by volume) dwarf planet in the known Solar System.
Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around 7,500 light-years (2,300 parsecs) distant in the constellation Carina.
The European Southern Observatory (ESO) is a 15-nation intergovernmental research organization for ground-based astronomy.
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer.
Fenrir or Saturn XLI (provisional designation S/2004 S 16) is a natural satellite of Saturn.
First magnitude stars are the brightest stars in the night sky, with a magnitude of -1, 0 and +1.
Flux describes the quantity which passes through a surface or substance.
The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective.
Full width at half maximum (FWHM) is an expression of the extent of function given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value.
In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic explosions that have been observed in distant galaxies.
Ganymede (Jupiter III) is the largest and most massive moon of Jupiter and in the Solar System.
General relativity (GR, also known as the general theory of relativity or GTR) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.
GRB 080319B was a gamma-ray burst (GRB) detected by the Swift satellite at 06:12 UTC on March 19, 2008.
Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 74–79 years.
Haumea, minor-planet designation 136108 Haumea, is a dwarf planet located beyond Neptune's orbit.
In the context of ancient Greek art, architecture, and culture, Hellenistic Greece corresponds to the period between the death of Alexander the Great in 323 BC and the annexation of the classical Greek heartlands by the Roman Republic.
Hipparchus of Nicaea (Ἵππαρχος, Hipparkhos) was a Greek astronomer, geographer, and mathematician.
The Solar System and all of the visible stars are in different orbits about the core of the Milky Way galaxy.
The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.
Humans (taxonomically Homo sapiens) are the only extant members of the subtribe Hominina.
The human eye is an organ which reacts to light and pressure.
Hydra is the outermost known moon of Pluto.
Iapetus (Ιαπετός), or occasionally Japetus, is the third-largest natural satellite of Saturn, eleventh-largest in the Solar System, and the largest body in the Solar System known not to be in hydrostatic equilibrium.
Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.
Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared (IR) radiation.
An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator.
The International Space Station (ISS) is a space station, or a habitable artificial satellite, in low Earth orbit.
The inverse-square law, in physics, is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.
In radiometry, irradiance is the radiant flux (power) received by a surface per unit area.
The James Webb Space Telescope (JWST) is a space telescope developed in collaboration between NASA, the European Space Agency, and the Canadian Space Agency that will be the scientific successor to the Hubble Space Telescope.
The jansky (symbol Jy) is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy.
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in Pasadena, California, United States, with large portions of the campus in La Cañada Flintridge, California.
JPL Horizons On-Line Ephemeris System provides easy access to key Solar System data and flexible production of highly accurate ephemerides for Solar System objects.
Jupiter is the fifth planet from the Sun and the largest in the Solar System.
K correction is a correction to an astronomical object's magnitude (or equivalently, its flux) that allows a measurement of a quantity of light from an object at a redshift z to be converted to an equivalent measurement in the rest frame of the object.
The Kreutz sungrazers (pronounced kroits) are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion.
The Kuiper belt, occasionally called the Edgeworth–Kuiper belt, is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun.
The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way.
LBV 1806-20 is a candidate luminous blue variable (LBV) and likely binary star located nearly 40,000 light-years from the Sun, towards the center of the Milky Way.
The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.
This is a list of the brightest naked eye stars to +2.50 magnitude, as determined by their maximum, total, or combined apparent visual magnitudes as seen from Earth.
This list of nearest bright stars is a table of stars found within 15 parsecs (48.9 light-years) of the Sun that have an absolute magnitude of +8.5 or brighter, which is approximately comparable to a listing of stars more luminous than a red dwarf.
The following two lists include all the known stars and brown dwarfs that are within of the Sun, or were/will be within in the astronomically near past or future.
In mathematics, the logarithm is the inverse function to exponentiation.
A logarithmic scale is a nonlinear scale used when there is a large range of quantities.
In astronomy, luminosity is the total amount of energy emitted per unit of time by a star, galaxy, or other astronomical object.
Luminosity distance DL is defined in terms of the relationship between the absolute magnitude M and apparent magnitude m of an astronomical object.
The lux (symbol: lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area.
In astronomy, magnitude is a logarithmic measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths.
Makemake (minor-planet designation 136472 Makemake) is a dwarf planet and perhaps the largest Kuiper belt object in the classical population, with a diameter approximately two thirds that of Pluto.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.
Mercury is the smallest and innermost planet in the Solar System.
Messier 41 (also known as M41 or NGC 2287) is an open cluster in the Canis Major constellation.
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away, in the constellation Ursa Major.
The Milky Way is the galaxy that contains our Solar System.
Monochrome describes paintings, drawings, design, or photographs in one color or values of one color.
Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
Norman Robert Pogson, CIE (23 March 1829 – 23 June 1891) was an English astronomer who worked in India at the Madras observatory.
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical instrument, such as a telescope or microscope.
The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.
Neptune is the eighth and farthest known planet from the Sun in the Solar System.
New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.
New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.
In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude.
The term night sky, usually associated with astronomy from Earth, refers to the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon.
Nix is a natural satellite of Pluto.
In mathematics, non-Euclidean geometry consists of two geometries based on axioms closely related to those specifying Euclidean geometry.
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.
In positional astronomy, two astronomical objects are said to be in opposition when they are on opposite sides of the celestial sphere, as observed from a given body (usually Earth).
The opposition surge (sometimes known as the opposition effect, opposition spike or Seeliger effect) is the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer.
The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.
A passband is the range of frequencies or wavelengths that can pass through a filter.
The perihelion of any orbit of a celestial body about the Sun is the point where the body comes nearest to the Sun.
In astronomy a phase curve describes the brightness of a reflecting body as a function of its phase angle.
Photosensors or photodetectors are sensors of light or other electromagnetic energy.
Photographic film is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals.
Before the advent of photometers which accurately measure the brightness of astronomical objects, the apparent magnitude of an object was obtained by taking a picture of it with a camera.
In astronomy, a photometric system is a set of well-defined passbands (or filters), with a known sensitivity to incident radiation.
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation.
Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The law is named after Max Planck, who proposed it in 1900.
Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune.
Polaris, designated Alpha Ursae Minoris (Ursae Minoris, abbreviated Alpha UMi, UMi), commonly the North Star or Pole Star, is the brightest star in the constellation of Ursa Minor.
In statistics, a power law is a functional relationship between two quantities, where a relative change in one quantity results in a proportional relative change in the other quantity, independent of the initial size of those quantities: one quantity varies as a power of another.
Claudius Ptolemy (Κλαύδιος Πτολεμαῖος, Klaúdios Ptolemaîos; Claudius Ptolemaeus) was a Greco-Roman mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.
A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).
Rayleigh scattering (pronounced), named after the British physicist Lord Rayleigh (John William Strutt), is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.
A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses) in a late phase of stellar evolution.
Rigel, also designated Beta Orionis (β Orionis, abbreviated Beta Ori, β Ori), is generally the seventh-brightest star in the night sky and the brightest star in the constellation of Orion—though periodically it is outshone within the constellation by the variable Betelgeuse.
A Ritchey–Chrétien telescope (RCT or simply RC) is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors (coma).
Satellite flare, also known as satellite glint, is the visible phenomenon caused by the reflective surfaces of passing satellites (such as antennas, SAR or solar panels), reflecting sunlight toward the Earth below and appearing as a brief, bright "flare".
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.
Sirius (a romanization of Greek Σείριος, Seirios,."glowing" or "scorching") is a star system and the brightest star in the Earth's night sky.
SN 1006 was a supernova that is likely the brightest observed stellar event in recorded history, reaching an estimated −7.5 visual magnitude, and exceeding roughly sixteen times the brightness of Venus.
SN 1054 is a supernova that was first observed on 4 July 1054, and remained visible for around two years.
SN 1987A was a peculiar type II supernova in the Large Magellanic Cloud, a dwarf galaxy satellite of the Milky Way.
A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength).
In spectroscopy, spectral flux density is the quantity that describes the rate at which energy is transferred by electromagnetic radiation through a real or virtual surface, per unit surface area and per unit wavelength.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
In astronomy, stellar classification is the classification of stars based on their spectral characteristics.
Stevens's power law is a proposed relationship between the magnitude of a physical stimulus and its perceived intensity or strength.
is the flagship telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii.
The Sun is the star at the center of the Solar System.
Supergiants are among the most massive and most luminous stars.
Supernova impostors are stellar explosions that appear at first to be a type of supernova but do not destroy their progenitor stars.
In astronomy, surface brightness quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background.
A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).
The Astrophysical Journal, often abbreviated ApJ (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler.
Titan is the largest moon of Saturn.
The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum.
Triton is the largest natural satellite of the planet Neptune, and the first Neptunian moon to be discovered.
The UBV photometric system (Ultraviolet, Blue, Visual), also called the Johnson system (or Johnson-Morgan system), is a wide band photometric system for classifying stars according to their colors.
Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.
Uranus is the seventh planet from the Sun.
Vega, also designated Alpha Lyrae (α Lyrae, abbreviated Alpha Lyr or α Lyr), is the brightest star in the constellation of Lyra, the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
Visual perception is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment.
The Weber–Fechner law refers to two related laws in the field of psychophysics, known as Weber's law and Fechner's law.
Zeta1 Scorpii (Zeta1 Sco, ζ1 Scorpii, ζ1 Sco) is a B-type hypergiant star in the constellation of Scorpius.
10 Hygiea is the fourth-largest asteroid in the Solar System by volume and mass, and it is located in the asteroid belt.
Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and is one of the largest asteroids in the Solar System.
2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.
2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.
2060 Chiron, provisional designation, and also known as 95P/Chiron, is a minor planet in the outer Solar System, orbiting the Sun between Saturn and Uranus.
3C 273 is a quasar located in the constellation Virgo.
Vesta, minor-planet designation 4 Vesta, is one of the largest objects in the asteroid belt, with a mean diameter of.
7 Iris is a large main-belt asteroid orbiting the Sun between Mars and Jupiter.
90377 Sedna is a large minor planet in the outer reaches of the Solar System that was,, at a distance of about 86 astronomical units (AU) from the Sun, about three times as far as Neptune.
Apparant magnitude, Apparent Magnitude, Apparent Visual Brightness, Apparent Visual Magnitude, Apparent bightness, Apparent bolometric magnitude, Apparent brightness, Apparent luminosity, Apparent visual magnitude, Apparent visual magnitudes, Fifth magnitude star, Optical magnitude, Pogson's Ratio, Pogson's ratio, Pogsons ratio, Second magnitude star, Sixth magnitude star, Stellar magnitude, V magnitude, Visible magnitude, Visual brightness, Visual magnitude.