dwarf galaxy
A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is so ...
Canes Venatici
Canes Venatici () is one of the 88 constellations designated by the International Astronomical Union (IAU). It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for 'hunting dogs', and ...
. The galaxy is formally classified as a Sm galaxy, which means that its structure vaguely resembles the structure of
spiral galaxies
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''Magellanic spiral
Magellanic spiral galaxies are (usually) dwarf galaxies which are classified as the type Sm (and SAm, SBm, SABm). They are galaxies with one single spiral arm, and are named after their prototype, the Large Magellanic Cloud, an SBm galaxy. They ca ...
because of its resemblance to the
Magellanic clouds
The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because bo ...
.
Structure
Unlike most
spiral galaxies
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''spiral arm
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae'' This galaxy was included in the ''
Atlas of Peculiar Galaxies
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 ...
'' as one of three examples of nearby galaxies with single spiral arms. Although NGC 4618 is labeled as peculiar, many similar galaxies have been identified.
It has been hypothesized that this galaxy's asymmetric structure may be the result of a
gravitational interaction
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
with
NGC 4625
NGC 4625 is a distorted dwarf galaxy in the constellation Canes Venatici. The galaxy is formally classified as a Sm galaxy, which means that its structure vaguely resembles the structure of spiral galaxies. The galaxy is sometimes referred to ...
. Such asymmetric structure is commonly seen among many interacting galaxies. However, observations of neutral
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
gas in NGC 4618 and NGC 4625 imply that only some of the gas outside the optical disks of NGC 4618 is affected by the gravitational interaction. This may indicate that NGC 4618's one-arm shape forms as the result of processes that are intrinsic to the galaxy itself.
Environment
As mentioned above, NGC 4618 is
interacting
Interaction is action that occurs between two or more objects, with broad use in philosophy and the sciences. It may refer to:
Science
* Interaction hypothesis, a theory of second language acquisition
* Interaction (statistics)
* Interactions o ...
with
NGC 4625
NGC 4625 is a distorted dwarf galaxy in the constellation Canes Venatici. The galaxy is formally classified as a Sm galaxy, which means that its structure vaguely resembles the structure of spiral galaxies. The galaxy is sometimes referred to ...
.
See also
*
Canes II Group
The Canes II Group or Canes Venatici II Group (CVn II Group) is a group of galaxies about 26.1 million light-years away from Earth. The group resides in the Local Supercluster. G. De Vaucouleurs, 1975. ''Nearby Groups of Galaxies'', ch. 5. the ne ...
*
NGC 5713
NGC 5713 is a peculiar, asymmetric galaxy in the constellation Virgo. Although classified as a spiral galaxy by most galaxy catalogs, NGC 5713 is very different from most normal spiral galaxies. While most spiral galaxies either have either two ...