NGC 4253
Galaxy in the constellation of Coma Berenices
From Wikipedia, the free encyclopedia
NGC 4253 is a barred spiral galaxy located in the constellation Coma Berenices. It is located at a distance of about 185 million light years from Earth, which, given its apparent dimensions, means that NGC 4253 is about 65,000 light years across.[1] It was discovered by William Herschel on February 3, 1788.[2] It is a Seyfert galaxy.[1]
| NGC 4253 | |
|---|---|
NGC 4253 by the Hubble Space Telescope | |
| Observation data (J2000 epoch) | |
| Constellation | Coma Berenices |
| Right ascension | 12h 18m 26.5s[1] |
| Declination | +29° 48′ 46″[1] |
| Redshift | 0.012882 ± 0.000050 [1] |
| Heliocentric radial velocity | 3,862 ± 15 km/s[1] |
| Distance | 185 Mly (56.6 Mpc)[1] |
| Apparent magnitude (V) | 13.5 |
| Characteristics | |
| Type | (R')SB(s)a [1] |
| Apparent size (V) | 1.0′ × 0.8′[1] |
| Notable features | Seyfert galaxy |
| Other designations | |
| UGC 7344, MRK 766, MCG +05-29-051, PGC 39525[1] | |
Characteristics
The NGC 4253 is a barred galaxy with thick bar, while the arms form a ring. Marquez et al. suggested that the galaxy has a secondary bar perpendicular to the main bar,[3] although that could be an artifact due to the presence of strong dust lanes and no inner bar is visible in images by WFPC2 F606W of the Hubble Space Telescope.[4] There is evidence of star formation along the dust lanes in the leading edge of the bar, especially at the east half.[5]
The nucleus of NGC 4253 has been found to be active and it has been categorised as a narrow line type I Seyfert galaxy.[6] The most accepted theory for the energy source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole. The mass of the black hole in the centre of NGC 5506 is estimated to be 1–13 × 106 M☉ based on reverberation mapping of the hydrogen lines,[7] 1.6+1.4
−1.2×106 M☉ based on time lag spectra,[8] and 1.26+1.00
−0.77×106 M☉ based on X-ray variations.[9]
The nucleus emits X-rays. The X-rays have been found to vary in intensity, exhibiting quasi-periodic oscillation, although this phenomenon appears to be transient.[10] The variability was found by ROSAT X-ray satellite.[11] The intensity varied by a factor of 3 every 6,450 seconds (about 1.8 hours) based on observations by XMM-Newton in 2005,[10] while in 2000 that period was estimated to be 4,200 seconds.[12] It has been suggested that the source of the oscillation lies at the inner part of the accretion disk.[10]
The galaxy has been found to host a maser and is a compact source in radiowaves.[13]
