| NGC 1142 | |
|---|---|
 NGC 1142 (left) by theHubble Space Telescope | |
| Observation data (J2000epoch) | |
| Constellation | Cetus |
| Right ascension | 02h 55m 12.1s[1] |
| Declination | −00° 11′ 01″[1] |
| Redshift | 0.028847 ± 0.000047[1] |
| Heliocentric radial velocity | 8,648 ± 14km/s[1] |
| Distance | 375Mly (115Mpc)[1] |
| Apparent magnitude (V) | 12.8[2] |
| Characteristics | |
| Type | S pec (Ring B)[1] |
| Size | 424,000 ly (130 kpc) |
| Apparent size (V) | 1.4 x 1.2arcmin (secondary)[3] and 1.56 x 0.83arcmin (primary)[4] |
| Notable features | Seyfert galaxy |
| Other designations | |
| NGC 1144,UGC 2389,Arp 118, VV 331a,Mrk 1504, CGCG 389-046,MCG +00-08-048,PGC 11012[1] | |
NGC 1142 (also known asNGC 1144) is a distortedspiral galaxy in the constellation ofCetus. It is located about 370 millionlight years away fromEarth, NGC 1142 is approximately 420,000 light years across. It is a type 2Seyfert galaxy. Itinteracts with the elliptical galaxyNGC 1141.
It was discovered byAlbert Marth on October 5, 1864, who noted a location 40 arcminutes north of the real location, and it was discovered independently on November 17, 1876, byÉdouard Stephan.[5]
NGC 1142 is aspiral galaxy which interacts with theelliptical galaxy NGC 1141. The linear separation of the two galaxies is 40 arcseconds, which corresponds to about 20 kiloparsecs at the distance of NGC 1142.[6] The closest encounter took place 22 million years before the observed moment and created adensity wave across NGC 1142, which resulted in the formation of knots of gas and stars,[7] and led to the distortion of the spiral galaxy, creating a knotty loop or ring that extends towards NGC 1141[6] and an off-centre nucleus.[8] A stellar bridge connects the two galaxies.[9]
The totalinfrared luminosity of the galaxy is2.2×1011 L☉, and thus it is categorised as aluminous infrared galaxy.[10] Much of the mid-infrared emission originates from a massive extra-nuclearstar formation region.[9] Very large star clusters, categorised assuper star clusters, have been formed in the loops, as a result of the increased gas density created by the density waves of the impact.[7]
The gas dynamics in the galaxy are characterised by the very large velocity range, which is up to 1,100 m/s for theCO emission. NGC 1142 is one of the most luminous galaxies in the local universe as far as CO emission is concerned, twice as bright as the merger remnantArp 220. Most of the emission originates from the ring, and especially its southern part, and a giantHII region west of the nucleus.[8]
The nucleus of NGC 1142 has been found to beactive and it has been categorised as a type IISeyfert galaxy. The most accepted theory for the energy source of active galactic nuclei is the presence of anaccretion disk around asupermassive black hole. The mass of the black hole in the centre of NGC 1142 is estimated to be 10(8.40 ± 0.21) (155–410 million)M☉.[11]
