NGC 4902
NGC 4902 is a barred spiral galaxy in the constellation Virgo. The galaxy lies about 110 million light years away from Earth, which means, given its apparent dimensions, that NGC 4902 is approximately 100,000 light years across. It was discovered by William Herschel on February 8, 1785.
Characteristics
NGC 4902 has a prominent bar. There is a brighter stellar feature visible on the southwest side of the bar, but it could also be superimposed. Two spiral arms emerge at the ends of the bar and overlap, forming an inner ring. There is a kink at the north side of the ring. Three spiral arms emanate from the ring, along with a fainter arm. The third arm appears semi-detacted from the inner ring. The arms are diffuse and feature many HII regions. The star formation rate of the galaxy is estimated to be 3.8 per year.Supernovae
Three supernovae have been observed in NGC 4902:- SN 1979E was discovered on a photographic plate exposed on 19 August 1979 by M. Wischnjewsky at an apparent magnitude of 16.
- SN 1991X was discovered by Robert Evans on 5 May 1991 at an estimated apparent magnitude of 13.5–14. It was located on the edge of the bar, near the inner ring. It was identified spectrographically as a type Ia supernova near maximum light.
- SN 2011A was discovered on 4 January 2011 by the CHASE project using the 0.41-m 'PROMPT 4' telescope at Cerro Tololo Inter-American Observatory at an apparent magnitude of 16.9. It was initially classified spectrographically as a type IIn supernova, however due to its low luminosity and low ejecta velocity has been suggested to be a supernova impostor.