NGC 4618
Encyclopedia
NGC 4618 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 as a Magellanic spiral
because of its resemblance to the Magellanic clouds
.
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 with NGC 4625
. Such asymmetric structure is commonly seen among many interacting galaxies. However, observations of neutral hydrogen
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.
.
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Canes Venatici
Canes Venatici
Canes Venatici is one of the 88 official modern constellations. 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 constellation is often depicted in illustrations as representing the dogs of Boötes the...
. 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 as a Magellanic spiral
Magellanic spiral
Magellanic spiral galaxies are galaxies which are classified as the type Sm . They are galaxies with one spiral arm, and are named after their prototype, the Large Magellanic Cloud, an SBm galaxy....
because of its resemblance to the Magellanic clouds
Magellanic Clouds
The two Magellanic Clouds are irregular dwarf galaxies visible in the southern hemisphere, which are members of our Local Group and are orbiting our Milky Way galaxy...
.
Structure
Unlike most spiral galaxies, NGC 4618 has a single spiral arm, which gives the galaxy an asymmetric appearance. This galaxy was included in the Atlas of Peculiar GalaxiesAtlas of Peculiar Galaxies
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology....
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 with NGC 4625
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...
. Such asymmetric structure is commonly seen among many interacting galaxies. However, observations of neutral hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
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 with NGC 4625NGC 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...
.