NGC 4639 is a barred spiral galaxy located in the

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Virgo. It was discovered by German-born astronomer William Herschel on April 12, 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 The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

. It is a companion to NGC 4654, and the two appear to have interacted roughly 500 million years ago. NGC 4639 is a member of the Virgo Cluster. The morphological classification of this galaxy is SAB(rs)bc, indicating a spiral galaxy with a weak bar (SAB), an incomplete ring around the bar (rs), and moderate to loosely-wound spiral arms (bc). NGC 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 Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays. Several types of astrophysical objects emit X-rays. They include galaxy clusters, black holes in active galactic nuclei (AGN), ...

, and is variable on timescales of months to years. There is a supermassive black hole at the core with an estimated mass of . Two

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

e have been observed in NGC 4639. The classical

Type Ia Supernova A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white ...

SN 1990N was discovered in this galaxy on June 22, 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. SN 2018imf ( type IIP, mag. 15.7) was discovered on 14 November, 2018.Transient Name Server entry for SN 2018imf.
Retrieved 23 March 2023.

References

External links

* {{DEFAULTSORT:NGC 4639 Barred spiral galaxies Virgo Cluster Virgo (constellation) 4639 07884 42741 Seyfert galaxies