NGC 4639
Template:Short description Template:Sky Template:Infobox Galaxy
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".[1] This is a relatively nearby galaxy,[2] lying approximately 72 million light-years away from the Milky Way.[3] It is a companion to NGC 4654, and the two appear to have interacted roughly 500 million years ago.[4] NGCScript error: No such module "String".4639 is a member of the Virgo Cluster.[5]
The morphological classification of this galaxy is SAB(rs)bc,[6] indicating a spiral galaxy with a weak bar (SAB), an incomplete ring around the bar (rs), and moderate to loosely-wound spiral arms (bc). NGCScript error: No such module "String".4639 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.[2] There is a supermassive black hole at the core[7] with an estimated mass of Script error: No such module "val"..[8]
Supernovae
Two supernovae have been observed in NGC 4639:
- SNScript error: No such module "String".1990N (typeScript error: No such module "String".Ia, mag. 15.5) was discovered by E. Thouvenot on 22 June 1990, two weeks before reaching peak brightness.[9][10][11] It was positioned Script error: No such module "val". east and Script error: No such module "val". south of the galaxy core.[9] The brightness and proximity of this supernova event has allowed it to be used as a standard candle.[11]
- SNScript error: No such module "String".2018imf (type IIP, mag. 15.8) was discovered by Kōichi Itagaki on 14 November 2018.[12] [Note: while officially associated with NGC 4639, this supernova is actually much closer to the neighboring galaxy VCCScript error: No such module "String".1931.]
References
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