U.S. astronomers using NASA’s Swift satellite have discovered a rare event: two supernovas side by side in one galaxy. The scientists say large galaxies typically play host to three supernovas per century, but Galaxy NGC 1316 has had two supernovas in fewer than five months – and a total of four supernovas in 26 years. That makes NGC 1316 – a massive elliptical galaxy about 80 million light-years from Earth – the most prodigious known producer of supernovas. Although NGC 1316 recently merged with a spiral galaxy, astronomers are quick to note all four supernovas in NGC 1316 appear to be of a variety previously not associated with galaxy mergers and massive star formation. Scientists are using the satellite to investigate whether the high supernova rate is a coincidence or a result of the merger.

http://science.psu.edu/news-and-events/2006-news/Swift11-2006.htm