NGC 3239

NGC 3239 is an irregular galaxy in the constellation of Leo.^[2] The galaxy was discovered in 1784 by William Herschel^[3] and is part of the New General Catalogue. It harbors a large and relatively bright H II region in its southeastern section that was first cataloged by Russian astronomer Boris Vorontsov-Velyaminov as VV95b.^[4] It's believed that NGC 3239 is the result of a galactic merger with a low-mass galaxy.^[5]

NGC 3239
Image of NGC 3239 (top center) as taken by the Mount Lemmon Sky Center, the bright spot inside the irregular galaxy is SN 2012A
Observation data (J2000 epoch)
Constellation	Leo
Right ascension	10h 25m 06.24s[1]
Declination	+17° 09′ 37.8″[1]
Distance	86 Mly (26.4 Mpc)h−1 0.73
Apparent magnitude (B)	13.5[1]
Characteristics
Type	IB(s)mpec[1]
Other designations
Arp 263, UGC 5637, MCG +03-27-025, PGC 30560[1]

Supernova

One supernova has been observed in NGC 3239. SN 2012A (type II-P, mag. 14.6) was discovered by Bob Moore, Jack Newton, and Tim Puckett on 7 January 2012.^[6][7] It reached a peak visual magnitude of +13.6.^[8][9] Later analysis concluded that the progenitor was a red supergiant with 10 to 15 times the mass of the sun.^[10]