ⓘ Astronomical objects


Astronomical object

Astronomical object refers to something that astronomers study. It may be any body or structure in the observable universe. This includes objects like nebulas, star clusters, galaxy clusters, galaxies, stars, protostars, planets, satellites, comets, asteroids. Objects on the Earth are not usually included, except sometimes recently landed meteorites.


Lists of astronomical objects

This is a partial list of the various lists of astronomical objects which either exist, or should exist, in Wikipedia. List of exoplanets List of planetary moons List of planets List of nearest stars List of stars List of brightest stars List of asteroids List of trans-Neptunian objects List of comets Minor planets List of semiregular variable stars List of gamma-ray bursters List of quasars List of black holes List of traditional star names List of blazars List of globular clusters List of galaxies List of nearest galaxies List of stars with confirmed extrasolar planets List of pulsars Li ...


Near-Earth object

A near-Earth object is a Solar System object whose orbit brings it close to the Earth. Their least distance from the Sun, their perihelion, is less than 1.3 AU. NEOs include near-Earth asteroids NEAs and near-Earth comets. They include more than ten thousand near-Earth asteroids NEAs, near-Earth comets, some solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth. Collisions in the past have had a significant role in shaping the geological and biological history of the planet. In some cases NEOs hit the Earth. Most of these meteors explode ha ...


Dark nebula

Dark nebulae are astronomical objects. They do not emit or reflect light. They are seen when they hide stars and galaxies behind them. The astronomer Edward Emerson Barnard compiled a list of dark nebulae known as the Barnard Catalogue of Dark Markings in the Sky, or the Barnard Catalogue for short. The nebulae listed by Barnard have become known as Barnard objects. These are the best-known dark nebulae: Horsehead nebula Barnard 33 Snake nebula (also see Dark Horse nebula Pipe nebula also see Dark Horse nebula; includes Barnard 59, 77 and 78 Dark Doodad nebula Cone nebula Coalsack nebula D ...


Extinction (astronomy)

Interstellar extinction is when the electromagnetic radiation of an astronomical object is blocked and/or scattered by other astronomical objects and cosmic dust. Also known as galactic extinction when the object is in the Milky Way.


International Astronomical Union

The International Astronomical Union is an international group that brings together the national astronomical groups from around the world. It was created in 1919. It was created to promote and protect the science of astronomy by getting different nations to work together. Its members are professional astronomers from all over the world, and they all work on research and education in astronomy. The IAU has good relationships with groups that include amateur astronomers. "National Members" are usually people with a high level of professional astronomy. There are more than 10.000 active "Ind ...


Astronomical spectroscopy

Astronomical spectroscopy is the science of using spectroscopy to figure out what elements astronomical bodies, such as stars, planets and nebulae, are made of. It can also be used to work out how those objects are moving, using doppler shift. The study of spectroscopy and spectra is used in astronomy to help scientists study the whole spectrum of electromagnetic radiation, including visible light, which radiates from stars and other hot celestial objects. Spectroscopy can be used to find properties of distant stars and galaxies. It can find out their chemical composition, temperature, den ...


Unidentified flying object

A UFO is any object flying in the sky which cannot be identified by the person who sees it. Sometimes the object is investigated. If people can still not figure out what the object is after an investigation, it is called a UFO. If they figure out what the object is, it can no longer be called a UFO because it has been identified. Even though UFOs can be anything, people often use the word UFO when they are talking about alien spacecraft. Flying saucer is another word that is often used to describe an unidentified flying object.


Messier catalogue

The Messier Catalogue is a list of astronomical objects made by French astronomer Charles Messier in 1771. Messier was a comet hunter, and was annoyed by fuzzy objects which were not comets. He put together a list of these objects, with his assistant Pierre Mechain. The list uses numbers with an M in front. Messier was limited by the objects he could see from France, so the list is incomplete by todays standards. It remains popular because people have used it for centuries and they are familiar with it. The first edition covered 45 objects numbered M1 to M45. The total list published by Me ...



An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. A planet, for example, can pass in front of a star. Some occultations are eclipses. The word is often used in astronomy. It can also be used in a non-astronomical sense to describe when an object in the foreground occults objects in the background.


Kuiper belt

The Kuiper belt is an area of the Solar System beyond the orbit of Neptune to 50 AU from the Sun. The objects within the Kuiper Belt together with the members of the scattered disk beyond, are together called trans-Neptunian. Many objects such as dwarf planets in the Kuiper belt are much bigger than the ones in the asteroid belt and are round. At least some Kuiper belt objects are icebound. The first objects in the Kuiper belt to be found were Pluto and Charon moon but the belt was only identified and named in 1992 when more Kuiper belt objects KBOs were found. A few thousand have since be ...


Opposition (astronomy and astrology)

Opposition is a word used in observational astronomy. It is used when two objects in the sky are on the opposite side of the sky when viewed from the Earth. In particular, two planets are in opposition to each other when their ecliptic longitudes differ by 180°. When talking about a single object being in opposition, it is assumed to be opposite from the sun. The Moon is in opposition to the Sun when it is a full moon. The symbol of opposition is ☍. A planet or asteroid or comet is said to be "in opposition" when it is in opposition to the Sun as seen from the Earth. This is the best time ...


(524522) 2002 VE68

2002 VE 68 is an asteroid and a temporary quasi-satellite of Venus. It was the first quasi-satellite to be found around a planet in the Solar System. It looks like it travels around venus during one Venerean year but it actually orbits the Sun, not Venus.


120347 Salacia

120347 Salacia is a trans-Neptunian object in the Kuiper belt. It is approximately 850 kilometers in diameter. As of 2018, it is found about 44.8 astronomical units from the Sun.



A blazar is a very compact quasar. They have a presumed supermassive black hole at the center of an active, giant elliptical galaxy. Blazars are among the most energetic phenomena in the universe and are an important topic in astronomy. Blazars are one of a group of active galaxies that host active galactic nuclei AGN. An AGN is a region at the centre of a galaxy which has a much higher than normal luminosity over some or all of the electromagnetic spectrum. The name "blazar" was originally coined in 1978 by astronomer Edward Spiegel. Blazars are AGN with a relativistic jet which is pointi ...


Canis Major dwarf

The Canis Major dwarf galaxy or Canis Major overdensity is a disputed dwarf irregular galaxy in the Local Group. It is in the same part of the sky as the constellation Canis Major. The supposed small galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all. The Canis Major dwarf is classified as an irregular galaxy. It is now thought to be the closest neighbouring galaxy to our position in the Milky Way. It is about 25.000 light-years away from the Solar System, and 52.000 light-years from the Galactic centre. It has a ...



Earth is the planet we live on. It is the third planet from the Sun. It is the only planet known to have life on it. The Earth formed around 4.5 billion years ago. It is one of four rocky planets on the inside of the Solar System. The other three are Mercury, Venus, and Mars. The large mass of the Sun makes Earth move around it, just as the mass of Earth makes the moon move around it. Earth also turns around in space, so that different parts face the Sun at different times. Earth goes around the Sun once one year for every 365​ 1 ⁄ 4 times it turns around one day. Earth is the only planet ...


Einsteins Cross

Einsteins Cross is an image of a quasar which is light years or 2.500.000.000 parsecs away. The quasar sits directly behind ZW 2237+030, Huchras lens, the lensing galaxy. Four images of the same distant quasar appear around this foreground galaxy due to strong gravitational lensing. According to its redshift, the quasar is about 8 billion light years from Earth, while the lensing galaxy is only 400 million light years away. Amateur astronomers are able to see some of the cross using telescopes but it requires extremely dark skies and telescope mirrors with diameters of 18 inc ...


Ice giant

An ice giant is a huge planet made mostly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two known ice giants in the Solar System, Uranus and Neptune. In astrophysics and planetary science the term "ice" refers to volatile chemical compounds with freezing points above about 100 K −280 °F; −173 °C, such as water, ammonia, or methane, with freezing points of 273, 195, and 91 K, respectively. In the 1990s, it was realized that Uranus and Neptune are a distinct class of giant planet, separate from the other giant planets, Jupiter and Satur ...


Orion complex

The Orion complex is a huge star-forming area in the constellation of Orion. It is a large group of bright nebulae, dark clouds, and young star clusters. The cloud is between 1.500 and 1.600 light-years away and is hundreds of light-years across. Several parts of the nebula can be seen through binoculars and small telescopes. Some parts such as the Orion nebula are visible to the naked eye. The nebula is important because of its sheer size. It is also one of the most active regions of stellar formation that can be seen in the night sky. In it are protoplanetary discs and many very young st ...


Orion OB1 Association

The Orion OB1 stellar association is the group of hot giant stars in a large cluster. They are spectral types O and B. There are thousands of lower-mass stars also in this group, and some protostars. The association is part of the larger Orion Molecular Cloud Complex. It is the most closely studied OB association. The Orion OB1 association has these subgroups: Orion OB1c - the stars in Orions Sword: 42 Orionis, θ Orionis, and ι Orionis. These stars are about 3-6 million years old. Orion OB1d - the stars of the Orion Nebula and M43 the youngest stars Orion OB1a - the group of stars northwes ...


Planetary system

Planetary system is the general term for a star with planets and other objects in orbit around it. The solar system is one of these. It is now clear that many other stars have planetary systems. The 21st century has become a golden era of planetary system discovery. 1795 such planets in 1116 planetary systems, including 461 multiplanet systems. Hundreds more systems are unconfirmed. 2014 data The closest confirmed system is Gliese 832 at 14.8 light years ly with one confirmed planet, whereas the closest unconfirmed system is Alpha Centauri at 4.37 ly with a planet of Earth mass. The closes ...


Protoplanetary disk

A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young star that has just formed. Protoplanetary disks have radii up to 1000 AU. Protoplanetary disks have been seen around several young stars in our galaxy. Protoplanetary disks are thought to be thin structures. They have mass that is much smaller than the young star in the center.


Provisional designation in astronomy

A provisional designation in astronomy is the naming convention of astronomical objects as soon as they are found. The provisional designation is usually replaced by a permanent name once a good orbit has been calculated. With asteroids, so many have been found that many will never be named by the people who found them.



A quasi-satellite is an astronomical object that crosses a planets orbit during its own orbit. A quasi-satellites orbit around the Sun takes exactly the same time as the planets orbit. Its eccentricity is different from the eccentricity of the planet. The orbits of quasi-satellites are unstable and over time they will break free from the planets gravity.


Sagittarius A

Sagittarius A is a complex radio source at the galactic centre of the Milky Way. It is in the Sagittarius constellation, but hidden from view by large clouds of cosmic dust in the spiral arms of the Milky Way. It consists of three components: the remains of a supernova Sagittarius A East, the spiral structure Sagittarius A West, and a very bright compact radio source at the center of the spiral, Sagittarius A*. These three overlap: Sagittarius A East is the largest, West appears off-center within East, and A* is at the centre of West.


Sagittarius A*

Sagittarius A* is a bright astronomical radio source at the center of the Milky Way. It is in the direction of the constellations Sagittarius and Scorpius. The radio source is part of a larger astronomical feature known as Sagittarius A. Sagittarius A* is thought to be a supermassive black hole, like those that are at the centers of most spiral and elliptical galaxies. Observations of the star S2 in orbit around Sagittarius A* were used to show the presence of the Milky Ways central supermassive black hole. This led to the conclusion that Sagittarius A* is the site of that black hole.


Sloan Digital Sky Survey

The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P. Sloan Foundation, which made much of the funding.


Tychos Supernova

Tychos Supernova – also called SN 1572 or B Cassiopeiae – was a supernova of Type Ia in the constellation Cassiopeia. It is one of eight supernovae visible to the naked eye in historical records. It appeared in early November 1572 and was independently discovered by many people. It is called Tychos because Tycho Brahe published a book the next year about what he and other astronomers saw. The remains of the supernova was first detected by radio telescopes. It was often known as 3C 10, which is a radio-source designation, but now people call it Tychos supernova remnant. It can be seen by li ...


Void (astronomy)

In astronomy, voids are the empty spaces between filaments. Both filaments and Voids are one of the largest-scale structures in the Universe. There are no or few galaxies in voids. Most voids have a diameter of 11 to 150 Mpc. Especially large voids are the empty spaces without many superclusters. These voids are sometimes called supervoids. A 1994 official counting The structure of the Universe traced by rich clusters of galaxies. ", see References lists a total of 27 supervoids with a distance of up to 740 Mpc. Some of supervoids chosen from the list are given below.



Oumuamua is an object from another star system that visited our solar system. Its official name is 1I/2017 U1. Oumuamua is the first interstellar object that we know has passed through our solar system. Oumuamua was first discovered on 19 October 2017 using the Pan-STARRS1 telescope at the Haleakala Observatory in Hawaii. Its appearance is long and narrow, and it had a dark red color, similar to objects in the outer Solar System.