NGC 4861
Irregular galaxy in constellation Canes Venatici
From Wikipedia, the free encyclopedia
NGC 4861, also known as Arp 266, is a galaxy in the constellation Canes Venatici. It was discovered by William Herschel on May 1, 1785.[4]
| NGC 4861 | |
|---|---|
 Hubble Space Telescope image of NGC 4861, taken using the Advanced Camera for Surveys | |
| Observation data (J2000 epoch) | |
| Constellation | Canes Venatici |
| Right ascension | 12h 59m 02.340s[1] |
| Declination | +34° 51′ 33.98″[1] |
| Redshift | 0.002785[2] |
| Heliocentric radial velocity | 835[2] |
| Distance | 34.77 ± 15.99 Mly (10.662 ± 4.903 Mpc)[2] |
| Group or cluster | Virgo Cluster |
| Apparent magnitude (V) | 12.32 |
| Apparent magnitude (B) | 12.90 |
| Characteristics | |
| Type | SB(s)m[2] Im/BCD |
| Apparent size (V) | 0.797′ × 0.692′[1] |
| Other designations | |
| Arp 266, UGC 8098, MCG+06-29-003, PGC 44536[3] | |
Morphological classification of NGC 4861 has proved relatively difficult. Its mass, size, and rotational velocity are consistent with it being a spiral galaxy. However, due to its highly irregular shape, it may also be classified as a dwarf irregular galaxy.[5] In fact, since dwarf galaxies are less massive and have lower gravitational potentials, gases and other material for star formation can move within them much faster, causing the galaxy to become a specific type of starburst galaxy, called a blue compact dwarf galaxy.[5][3] It has also been described as a "comet-like" galaxy due to its resemblance to a comet.[6]
Two ultraluminous X-ray sources (ULXs) have been found within NGC 4861. The first, NGC 4861 X1, is associated with a dense H II region. The second, NGC 4861 X2, seems to be within a small star cluster near the "comet head" of NGC 4861. Assuming it is a star cluster, it has a mass of 400±80 M☉ and an age of 5 million years. Compared to other star clusters with which ULXs are associated, its mass is quite low.[6]
