Galaxies & Deep Sky
Galaxies, galaxy clusters, quasars, and deep-sky objects
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 120 light years in diameter.
Read commentary →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 characteristics indicating that this luminosity is not produced by the stars. Such excess, non-stellar emissions have been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray, and gamma ray wa
Read commentary →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 NGC 224.
Read commentary →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 starburst phase, in which the collision of clouds of gas and dust, with entangled magnetic fields, causes rapid star formation.
Read commentary →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, and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well.
Read commentary →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 – directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away f
Read commentary →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 of 57.69 kiloparsecs (188,200 light-years), and a mass of about 2.9–4.8 billion solar masses; its outer ring has a circular velocity of 217 km/s.
Read commentary →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 Parramatta, in New South Wales, Australia.
Read commentary →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 of the M81 Group, with the D25 isophotal diameter of 12.52 kiloparsecs (40,800 light-years).
Read commentary →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 comprising the Coma Supercluster.
Read commentary →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 contains gravitationally bound matter.
Read commentary →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 by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the Nebulae, along with spiral and lenticular galaxies.
Read commentary →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 ranging from 1014 to 1015 solar masses. Clusters consist of galaxies, heated gas, and dark matter.
Read commentary →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 interactions, including major interactions, minor interactions, and galaxy harassment.
Read commentary →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 tens of thousands to many millions of member stars, all orbiting in a stable, compact formation.
Read commentary →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 the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.
Read commentary →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- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (c.
Read commentary →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 largest and most massive galaxies in the local universe, it has a large population of globular clusters—about 15,000 compared with the 150–200 orbiting the Milky Way—and a jet of energetic plasma that
Read commentary →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.
Read commentary →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. Located at a distance of 17,090 light-years (5,240 parsecs), it is the largest known globular cluster in the Milky Way at a diameter of roughly 150 light-years.
Read commentary →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 clusters have been discovered within the Milky Way galaxy, and many more are thought to exist.
Read commentary →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 in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one
Read commentary →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.
Read commentary →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 Singapore Agency for Science, Technology and Research AStar, the Eurocopter AS350 Écureuil helicopter Class A star, a star of spectral class A Sagittarius A*, a radio source at the center of the Milky
Read commentary →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 (18,900 light-years), and contains several hundred million stars.
Read commentary →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 9.55 megaparsecs (31.1 million light-years) from the Milky Way galaxy. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Sup
Read commentary →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 galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge.
Read commentary →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 satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other.
Read commentary →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 formed from stars in other arms of the galaxy, which are so far away that they cannot be individually distinguished by the naked eye. The Milky Way is a barred spiral galaxy with a D25 isophotal diamet
Read commentary →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 constellation Taurus. At a distance of about 444 light-years, it is among the nearest star clusters to Earth and the nearest Messier object to Earth, being the most obvious star cluster to the naked ey
Read commentary →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.
Read commentary →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) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group (containing the Milky Way galaxy) is a member.
Read commentary →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 constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy.
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