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]
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 egde 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 × 106M☉ based on
reverberation mapping of the hydrogen lines,[7]1.6+1.4 −1.2×106M☉ based on time lag spectra,[8] and 1.26+1.00 −0.77×106M☉ 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]