Peculiar galaxy

A peculiar galaxy is a galaxy of unusual size, shape, or composition.[1] Between five and ten percent of known galaxies are categorized as peculiar.[2] Astronomers have identified two types of peculiar galaxies: interacting galaxies and active galactic nuclei (AGN).[3]

When two galaxies come close to each other, their mutual gravitational forces can cause them to acquire highly irregular shapes.[4] The terms 'peculiar galaxy' and 'interacting galaxy' have now become synonymous because the majority of peculiar galaxies attribute their forms to such gravitational forces.[2]

Extragalactic peculiarity
ESO 162-17 is an example of a peculiar galaxy 40 million light-years away in the constellation Carina.


Scientists hypothesize that many peculiar galaxies are formed by the collision of two or more galaxies.[4] As such, peculiar galaxies tend to host more active galactic nuclei than normal galaxies, indicating that they contain supermassive black holes.[2][4] Many peculiar galaxies experience starbursts, or episodes of rapid star formation, due to the galaxies merging.[2] The periods of elevated star formation and the luminosity resulting from active galactic nuclei cause peculiar galaxies to be slightly bluer in color than other galaxies.[2]

Studying peculiar galaxies can offer insights on other types of galaxies by providing useful information on galactic formation and evolution.[2] Arp mapped peculiar galaxies in his 1966 Atlas of Peculiar Galaxies. Arp states that "the peculiarities of the galaxies pictured in this Atlas represent perturbations, deformations, and interactions which should enable us to analyze the nature of the real galaxies which we observe and which are too remote to experiment on directly."


Peculiar galaxies are notated by an additional "p" or "pec" (depending on the exact convention) after the hubble type of the galaxy.[5]

See also

External links

  1. ^ "peculiar galaxy". 2007-02-01. Retrieved 2012-08-14.
  2. ^ a b c d e f Higdon, James L. Peculiar Galaxies. doi:10.1888/0333750888/2626.
  3. ^ "Peculiar Galaxies". Retrieved 2016-12-05.
  4. ^ a b c Millis, John P. "Peculiar Galaxies". Retrieved 17 December 2014.
  5. ^ Darling, David. "peculiar galaxy". Retrieved 2019-02-07.
34 (number)

34 (thirty-four) is the natural number following 33 and preceding 35.

Antennae Galaxies

The Antennae Galaxies, also known as NGC 4038/NGC 4039, 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. They were discovered by William Herschel in 1785.

Coma Filament

Coma Filament is a galaxy filament. The filament contains the Coma Supercluster of galaxies and forms a part of the CfA2 Great Wall.

Hoag's Object

Hoag's Object is a non-typical galaxy of the type known as a ring galaxy. The galaxy is named after Arthur Hoag who discovered it in 1950 and identified it as either a planetary nebula or a peculiar galaxy with eight billion stars.

Irregular galaxy

An 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.Collectively they are thought to make up about a quarter of all galaxies. Some irregular galaxies were once spiral or elliptical galaxies but were deformed by an uneven external gravitational force. Irregular galaxies may contain abundant amounts of gas and dust. This is not necessarily true for dwarf irregulars.Irregular galaxies are commonly small, about one tenth the mass of the Milky Way galaxy. Due to their small sizes, they are prone to environmental effects like crashing with large galaxies and intergalactic clouds.

List of galaxies named after people

A small number of galaxies or galaxy groups have been named after individual people. In most cases, the named individual was the person who discovered the object, who first brought attention to it, or who first studied it scientifically.

Many of the brighter galaxies visible from the Northern Hemisphere have Messier numbers, named after Charles Messier. For instance, the Andromeda Galaxy is Messier 31 and the Whirlpool Galaxy is Messier 51. There are a few other comprehensive catalogs that assign the cataloguer's name to galaxies. For instance, Markarian galaxies, named after Benjamin Markarian, are galaxies with excess blue and ultraviolet emission; galaxies in the Atlas of Peculiar Galaxies are assigned an Arp number after Halton Arp who produced the catalog; etc. Objects in these catalogs are excluded below, except in cases where they carry the name of an additional person.

Markarian 177

Markarian 177 is a blue compact dwarf galaxy located 90,000,000 ly (28 Mpc) away, at the constellation of Ursa Major, in the bowl of the Big Dipper asterism. It was discovered by the astronomer Benjamin Markarian.

Markarian 177 is a peculiar galaxy that is receding from us at a rate of 2425 km/s. It has a visual apparent size of 0.41×0.34 arcmin.

NGC 2685

NGC 2685 (also known as the Helix Galaxy) is a lenticular and polar ring Seyfert Type 2 galaxy in the constellation Ursa Major. It is about 50,000 light-years across and about 42 million light-years away from Earth. It is receding from Earth at 883 kilometers per second. It is an object of great scientific interest, because polar-ring galaxies are very rare galaxies. They are thought to form when two galaxies gravitationally interact with each other. "The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable."Allan Sandage referred to NGC 2685 as "perhaps the most peculiar galaxy in the Shapley-Ames Catalog".

NGC 2782

NGC 2782 is a peculiar spiral galaxy that formed after a galaxy merger in the constellation Lynx. The galaxy lies 75 million light years away from Earth, which means, given its apparent dimensions, that NGC 2782 is approximately 100,000 light years across. NGC 2782 has an active galactic nucleus and it is a starburst and a type 1 Seyfert galaxy. NGC 2782 is mentioned in the Atlas of Peculiar Galaxies in the category galaxies with adjacent loops.

NGC 3256

NGC 3256 is a peculiar galaxy formed from the collision of two separate galaxies in the constellation of Vela. NGC 3256 is located about 100 million light years away and belongs to the Hydra-Centaurus supercluster complex. NGC 3256 provides a nearby template for studying the properties of young star clusters in tidal tails. The system hides a double nucleus and a tangle of dust lanes in the central region. The telltale signs of the collision are two extended luminous tails swirling out from the galaxy. The tails are studded with a particularly high density of star clusters. NGC 3256 is the most luminous galaxy in the infrared spectrum located within z 0.01 from Earth.

NGC 4027

NGC 4027 (also known as Arp 22) is a barred spiral galaxy approximately 83 million light-years away in the constellation Corvus. It is also a peculiar galaxy because one of its spiral arms goes out more than the other. This is probably due to a galactic collision in NGC 4027's past.

NGC 4488

NGC 4488 is a lenticular galaxy located about 60 million light-years away in the constellation of Virgo. The galaxy was discovered by astronomer William Herschel on December 28, 1785. NGC 4488 is a member of the Virgo Cluster.

NGC 5474

NGC 5474 is a peculiar dwarf galaxy in the constellation Ursa Major. It is one of several companion galaxies of the Pinwheel Galaxy (M101), a grand-design spiral galaxy.

Among the Pinwheel Galaxy's companions, this galaxy is the closest to the Pinwheel Galaxy itself. The gravitational interaction between NGC 5474 and the Pinwheel Galaxy has strongly distorted the former. As a result, the disk is offset relative to the nucleus. The star formation in this galaxy (as traced by hydrogen spectral line emission) is also offset from the nucleus. NGC 5474 shows some signs of a spiral structure. As a result, this galaxy is often classified as a dwarf spiral galaxy, a relatively rare group of dwarf galaxies.

NGC 7252

NGC 7252 is a peculiar galaxy resulting from an interaction between two galaxies that started a billion years ago. It is located 220 million light years away in the constellation Aquarius. It is also called Atoms for Peace galaxy, a nickname which comes from its loop-like structure, made of stars, that resembles a diagram of an electron orbiting an atomic nucleus.

NGC 7257

NGC 7260 (NGC 7257) is a peculiar galaxy located in the constellation Aquarius.

NGC 7727

NGC 7727 is a peculiar galaxy in the constellation Aquarius.


Peculiar may refer to:

Peculiar (album), an album by The Slackers

Peculiar, a comic strip, later published as a book, by cartoonist Richard Sala

Peculiar, an ecclesiastical district, parish, chapel or church outside the jurisdiction of the bishop of the diocese in which it is situated

SN 2008ax

Supernova 2008ax was a type Ib supernova in Peculiar Galaxy NGC 4490. As the name indicates, it was discovered in 2008 on 3 March by LOSS and Koichi Itagaki. It was the third-brightest supernova of 2008.

Ursa Major Filament

Ursa Major Filament is a galaxy filament. The filament is connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.

Active nuclei
Energetic galaxies
Low activity
See also

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