NGC 2787 is a barred lenticular galaxy approximately 24[3] million light-years away in the northern constellation of Ursa Major. It was discovered on December 3, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer described it as, "bright, pretty large, a little extended 90°, much brighter middle, mottled but not resolved, very small (faint) star involved to the southeast".[9] The visible galaxy has an angular size of 2.5 × 1.5 arcminutes[7] or 3.24 × 1.81 arcminutes[10] and an apparent visual magnitude of 11.8.[4]
| NGC 2787 | |
|---|---|
 NGC 2787 as observed by the Hubble Space Telescope (HST). | |
| Observation data (J2000 epoch) | |
| Constellation | Ursa Major |
| Right ascension | 09h 19m 18.60430s[1] |
| Declination | +69° 12′ 11.6429″[1] |
| Heliocentric radial velocity | 627.3±13.2 km/s[2] |
| Distance | 24.17 ± 0.46 Mly (7.41 ± 0.14 Mpc)[3] |
| Apparent magnitude (V) | 11.79[4] |
| Apparent magnitude (B) | 12.92[4] |
| Absolute magnitude (B) | −18.84[5] |
| Characteristics | |
| Type | SB(r)0+[6] |
| Mass/Light ratio | 50[5] M☉/L☉ |
| Size | 5.5 kpc[5] |
| Apparent size (V) | 2′.530 × 1′.518[7] (NIR) |
| Notable features | Barred lenticular; LINER |
| Other designations | |
| PGC 26341, UGC 4914[8] | |
This galaxy is small and isolated[5] with a morphological classification of SB(r)0+,[6] which indicates a barred spiral (SB) with a ring around the bar (r). Being a lenticular galaxy, it has the large halo of an elliptical galaxy. The disk is inclined at an angle of 58°±3° to the line of sight from the Earth, with the major axis aligned along a position angle of 110°±3°.[5] The galaxy has an unusually high mass-to-light ratio, much greater than for a typical spiral galaxy.[5] The distribution of the galaxy's neutral hydrogen forms a clumpy ring with a radius of 10.3 kpc, double that of the visible galaxy, with a mass of 5.5×108 M☉.[5] This ring appears misaligned with the central disk.[11]
NGC 2787 contains a low-ionization nuclear emission-line region (LINER) at its core, which is a type of region that is characterized by its spectral line emission from weakly ionized atoms.[12] LINERs are very common within lenticular galaxies, with approximately one-fifth of nearby lenticular galaxies containing LINERs.[13] The supermassive black hole at the center has a mass of 4.1+0.4
−0.5×107 M☉.[14] The central region of the galaxy contains dust rings that are tilted with respect to the disk, which may be the result of an encounter with another galaxy.[11]
References
External links
Media related to NGC 2787 at Wikimedia Commons- A Galaxy That's All Wound Up
- NGC 2787 at ESA/Hubble
