| NGC 4861 | |
|---|---|
 Hubble Space Telescope image of NGC 4861, taken using theAdvanced Camera for Surveys | |
| Observation data (J2000epoch) | |
| 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 orcluster | 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] | |
NGC 4861, also known asArp 266, is agalaxy in theconstellationCanes Venatici. It was discovered byWilliam Herschel on May 1, 1785.[4]
Morphological classification of NGC 4861 has proved relatively difficult. Its mass, size, and rotational velocity are consistent with it being aspiral galaxy. However, due to its highly irregular shape, it may also be classified as adwarf irregular galaxy.[5] In fact, since dwarf galaxies are less massive and have lowergravitational potentials, gases and other material forstar formation can move within them much faster, causing the galaxy to become a specific type ofstarburst galaxy, called ablue compact dwarf galaxy.[5][3] It has also been described as a "comet-like" galaxy due to its resemblance to acomet.[6]
Twoultraluminous X-ray sources (ULXs) have been found within NGC 4861. The first, NGC 4861 X1, is associated with a denseH II region. The second, NGC 4861 X2, seems to be within a smallstar cluster near the "comet head" of NGC 4861. Assuming it is a star cluster, it has a mass of400±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]
Media related toNGC 4861 at Wikimedia Commons
