| NGC 3642 | |
|---|---|
 NGC 3642 as taken byMount Lemmon SkyCenter | |
| Observation data (J2000epoch) | |
| Constellation | Ursa Major |
| Right ascension | 11h 22m 17.9s[1] |
| Declination | 59° 04′ 28″[1] |
| Redshift | 1571 ± 3km/s[1] |
| Distance | 27 ± 35Mly (8.4 ± 10.7Mpc)[1] |
| Apparent magnitude (V) | 10.8 |
| Characteristics | |
| Type | SA(r)bc[1] |
| Apparent size (V) | 1.8′ × 1.5′[1] |
| Other designations | |
| UGC 6385,MCG +10-16-128,PGC 34889[1] | |
NGC 3642 is aspiral galaxy in the constellationUrsa Major. The galaxy has alow-ionization nuclear emission-line region. It is located at a distance of circa 30 millionlight years from Earth, which, given its apparent dimensions, means that NGC 3642 is about 50,000 light years across. The galaxy is characterised by an outer pseudoring, which was probably formed after the accretion of a gas richdwarf galaxy.[2]
NGC 3642 is a spiral galaxy without a bar.[2] In the nucleus there is asupermassive black hole with an estimated mass of 26-31 millionM⊙, based on the intrinsic velocity dispersion as measured by theHubble Space Telescope,[3] or 15 million M⊙, based on thebulge luminosities innear-infraredKs-band.[4]
Around the nucleus, a one-armed spiral forms a ring, and it is possible that it leads material towards the nucleus. The nucleus is surrounded by an inner flocculent spiral. The outer part of the spiral forms a pseudoring that extends for about half a circle. The outer part of the spiral is warped, while its main part features an ordinary differentially rotating disk. The HI gas is also warped and extends further on the western side.[2]
The galaxy belongs to the NGC 3642 group[5] (also known as the NGC 3610 group), agalaxy group that also includesNGC 3610,NGC 3619,NGC 3669,NGC 3674 andNGC 3683. Other nearby galaxies includeNGC 3440,NGC 3445,NGC 3458,NGC 3543 andNGC 3613.[6]
