Right ascension 12 15 05.0 Redshift 0.003620 Galactocentric velocity 1,093 km/s Constellation Coma Berenices | Declination +33° 11′ 50″ Helio radial velocity 1,083 km/s Magnitude 11.99 Apparent magnitude (V) 11.99 | |
Distance 49.84 ± 0.46 Mly (15.28 ± 0.14 Mpc) Similar NGC 4293, NGC 4448, NGC 4450, NGC 4262, NGC 4308 | ||
NGC 4203 is the New General Catalogue identifier for a lenticular galaxy in the northern constellation of Coma Berenices. It was discovered on March 20, 1787 by English astronomer William Herschel, and is situated 5.5° to the northwest of the 4th magnitude star Gamma Comae Berenices and can be viewed with a small telescope. The morphological classification of NGC 4203 is SAB0−, indicating that it has a lenticular form with tightly wound spiral arms and a weak bar structure at the nucleus.
This galaxy has a fairly large reservoir of neutral hydrogen containing on the order of a billion solar masses (M☉), but it is only undergoing a low rate of new star formation. Hence, the inner star formation of the galaxy is fairly old; roughly ten billion years on average. The neutral hydrogen is arranged in two ring-like structures, with the outer ring having nine times the mass of the inner. In the central region there is around 7007250000000000000♠2.5×107 M☉ of molecular hydrogen, plus dust structures within 980 ly (300 pc) of the nucleus. The gas in the outer disk may have been accreted from the inter-galactic medium, or captured during a close encounter with a dwarf galaxy.
The nucleus of the galaxy contains a low-ionization nuclear emission-line region of type 1.9. This is being generated by a supermassive black hole of an estimated 7007600000000000000♠(6±1)×107 M☉. An influx of gas of around 6998200000000000000♠2×10−2 M☉/yr is sufficient to explain the measured X-ray luminosity. The time-varying emissions from the region are perhaps best explained by an infalling asymptotic giant branch star that is losing mass to the black hole along a contrail.