The Catalina Sky Survey with the Mt. Bigelow 0.8m Catalina Schmidt Telescope has spotted a magnitude (V ~ 13, Optical Transient) object on the edge of a spiral arm on the Antennae Galaxies

Detection Date: 2007-12-18 12:49:10 UT
Date: 2007-12-18 UT 12:49:10
Position(2000): RA 12:01:52.80 Dec -18:58:21.72

Supernova 2007sr
At magnitude 13 this would be the brightest supernova this year.
As yet the type is unknown

The supernova in the Antennae (NGC 4038) has been confirmed as a type-Ia.
Swift Ultraviolet/Optical satellite telescope observations on 21st December show it to be magnitude V = 12.9 ±0.1