The light from an exploding star in the Messier 82 (aka "Cigar") galaxy was first photographed from Earth on January 22nd, 2013. The galaxy is ~12 million light years away so the explosion occurred about 12 million years ago.
A new supernova has not been observed so close to our solar system in over 20 years. This one was discovered by students and staff at the University of London Observatory. According to a press release, the discovery was a fluke.
"The weather was closing in, with increasing cloud," explains Dr Steve Fossey, "so instead of the planned practical astronomy class, I gave the students an introductory demonstration of how to use the CCD camera on one of the observatory’s automated 0.35–metre telescopes."
The students happened to choose M 82, since it was in one of the shrinking patches of clear sky. "While adjusting the telescope’s position," the press release reads, "Fossey noticed a ‘star’ overlaid on the galaxy which he did not recognize."
According to the astronomer Ray Jayawardhana, the supernova was "too far *and* of the wrong type" for neutrino detection.
Watch Jayawardhana explain how a supernova might be identified via neutrino detection in the video here: