NGC 4639

NGC 4639 is a barred spiral galaxy located in the equatorial constellation of Virgo. It was discovered by German-born astronomer William Herschel on 12 April 1784. John L. E. Dreyer described it as "pretty bright, small, extended, mottled but not resolved, 12th magnitude star 1 arcmin to southeast". This is a relatively nearby galaxy, lying approximately 72 million light-years away from the Milky Way. It is a companion to NGC 4654, and the two appear to have interacted roughly 500 million years ago. NGC4639 is a member of the Virgo Cluster.
The morphological classification of this galaxy is SABbc, indicating a spiral galaxy with a weak bar, an incomplete ring around the bar, and moderate to loosely-wound spiral arms. NGC4639 has a mildly active galactic nucleus of the Seyfert type 1; one of the weakest known. The compact central source has been detected by its X-ray emission, and is variable on timescales of months to years. There is a supermassive black hole at the core with an estimated mass of.

Supernovae

Two supernovae have been observed in NGC 4639:

SN1990N was discovered by E. Thouvenot on 22 June 1990, two weeks before reaching peak brightness. It was positioned east and south of the galaxy core. The brightness and proximity of this supernova event has allowed it to be used as a standard candle.
SN2018imf was discovered by Kōichi Itagaki on 14 November 2018.