NGC 6240, also known as the Starfish Galaxy, is a nearby ultraluminous infrared galaxy (ULIRG) in the constellation Ophiuchus. The galaxy is the remnant of a merger between three smaller galaxies. The collision between the three progenitor galaxies has resulted in a single, larger galaxy with three distinct nuclei and a highly disturbed structure, including faint extensions and loops.
A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. For example, the star formation rate of the Milky Way galaxy is approximately 3 M☉/yr, while starburst galaxies can experience star formation rates of 100 M☉/yr or more. In a starburst galaxy, the rate of star formation is so large that the galaxy consumes all of its gas reservoir, from which the stars are forming, on a timescale much shorter than the age of the galaxy. As such, the starburst nature of a galaxy is a phase, and one that typically occupies a brief period of a galaxy's evolution. The majority of starburst galaxies are in the midst of a merger or close encounter with another galaxy. Starburst galaxies include M82, NGC 4038/NGC 4039, and IC 10.
Halton Christian "Chip" Arp was an American astronomer. He was known for his 1966 book Atlas of Peculiar Galaxies, which documented peculiarities among galaxies.
A ring galaxy is a galaxy with a circle-like appearance. Hoag's Object, discovered by Arthur Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.
Interacting galaxies are galaxies whose gravitational fields result in a disturbance of one another. An example of a minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms. An example of a major interaction is a galactic collision, which may lead to a galaxy merger.
NGC 3226 is a dwarf elliptical galaxy that is interacting with the spiral galaxy NGC 3227. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo. It is a member of the NGC 3227 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.
NGC 520 is a pair of colliding spiral galaxies about 105 million light-years away in the constellation Pisces. They were discovered by astronomer William Herschel on 13 December 1784.
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp in 1966. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology. The primary goal of the catalog was to present photographs of examples of the different kinds of peculiar structures found among galaxies.
Arp 220 is the result of a collision between two galaxies which are now in the process of merging. It is the 220th object in Halton Arp's Atlas of Peculiar Galaxies.
A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. Conversely, the spectral line emission from strongly ionized atoms, such as O++, Ne++, and He+, is relatively weak. The class of galactic nuclei was first identified by Timothy Heckman in the third of a series of papers on the spectra of galactic nuclei that were published in 1980.
The NGC 5679 group, also known as Arp 274, is a triplet of galaxies, MCG+1-37-36, MCG+1-37-35 and MCG+1-37-34, spanning about 200000 light-years and at some 400 million light-years from Earth in the constellation Virgo. Arp 274 refers to the Atlas of Peculiar Galaxies, compiled by Halton Arp in 1966. Galaxies 269 through 274 in his catalogue are galaxies that appear to have connected arms.
Arp 273 is a pair of interacting galaxies, 300 million light years away in the constellation Andromeda. It was first described in the Atlas of Peculiar Galaxies, compiled by Halton Arp in 1966. The larger of the spiral galaxies, known as UGC 1810, is about five times more massive than the smaller galaxy. It has a disc that is tidally distorted into a rose-like shape by the gravitational pull of the companion galaxy below it, known as UGC 1813. The smaller galaxy shows distinct signs of active star formation at its nucleus, and "it is thought that the smaller galaxy has actually passed through the larger one."
The Multiwavelength Atlas of Galaxies is a textbook and atlas of 35 well studied galaxies authored by Glen Mackie of the Centre for Astrophysics & Supercomputing, Swinburne University of Technology. It was originally published in 2011 by Cambridge University Press.
NGC 7727 is a peculiar galaxy in the constellation Aquarius. It harbors two galactic nuclei, each containing a supermassive black hole, separated 1,600 light years apart.
NGC 4490, also known as the Cocoon Galaxy, is a barred spiral galaxy in the constellation Canes Venatici. William Herschel discovered it in 1788. It is known to be of the closest interacting/merging galactic system. The galaxy lies at a distance of 25 million light years from Earth making it located in the local universe. It interacts with its smaller companion NGC 4485 and as a result is a starburst galaxy. NGC 4490 and NGC 4485 are collectively known in the Atlas of Peculiar Galaxies as Arp 269. The two galaxies has already made their closest approach and are rushing away from each other. It's been discovered that NGC 4490 has a double nucleus.
NGC 1614 is the New General Catalogue identifier for a spiral galaxy in the equatorial constellation of Eridanus. It was discovered on December 29, 1885 by American astronomer Lewis Swift, who described it in a shorthand notation as: pretty faint, small, round, a little brighter middle. The nebula was then catalogued by Danish-Irish astronomer J. L. E. Drayer in 1888. When direct photography became available, it was noted that this galaxy displayed some conspicuous peculiarities. American astronomer Halton Arp included it in his 1966 Atlas of Peculiar Galaxies. In 1971, Swiss astronomer Fritz Zwicky described it as a "blue post-eruptive galaxy, compact patchy core, spiral plumes, long blue jet SSW".
NGC 7469 is an intermediate spiral galaxy in the constellation of Pegasus. NGC 7469 is located about 200 million light-years away from Earth, which means, given its apparent dimensions, that NGC 7469 is approximately 90,000 light-years across. It was discovered by William Herschel on November 12, 1784.
NGC 7130 is a spiral galaxy located in the constellation Piscis Austrinus. It is located at a distance of about 220 million light years from Earth, which, given its apparent dimensions, means that NGC 7130 is about 100,000 light years across. It was discovered by John Herschel on September 25, 1834, and discovered independently by Lewis Swift on September 17, 1897. The location of the galaxy given in the New General Catalogue was off by 30 arcminutes in declination from the location of the galaxy.
NGC 1142 is a distorted spiral galaxy in the constellation of Cetus. It is located about 370 million light years away from Earth, which means, given its apparent dimensions, that NGC 1142 is approximately 170,000 light years across. It is a type 2 Seyfert galaxy. It interacts with the elliptical galaxy NGC 1141.
NGC 7678 is an intermediate spiral galaxy located in the constellation Pegasus. It is located at a distance of about 130 million light years from Earth, which, given its apparent dimensions, means that NGC 7678 is about 95,000 light years across. It was discovered by William Herschel on September 15, 1784.
