Nov 22, 2006
NGC 1316 has experienced a merger in the recent past
The galaxy, known as NGC 1316, has now hosted four supernovae in 26 years, making it one of the most prodigious known producers of these events.
The explosions were both initially detected from the ground by a South African amateur astronomer.
Berto Monard's discovery was followed by detailed professional study with Nasa's Swift space telescope.
The first supernova, still visible on the "right" in this image, was detected on 19 June and was named SN 2006dd.
The second supernova, on the immediate "left" in the image, was detected on 5 November and has been named SN 2006mr.
The other objects in the image include a central bright spot, which is the galaxy core, and a bright object like an earring to the far left which is a foreground star.
Large galaxies typically play host to three supernovae per century - which underlines the rarity of this double event.
Both were of the Type 1a variety, thought to form when a white dwarf - the remains of a low or medium mass star - pulls enough matter from a nearby companion star to produce a catastrophic explosion.
Their uniform brightness is used to measure distances in the Universe.
NGC 1316 is a massive elliptical galaxy about 80 million light-years from Earth, and has recently merged with a spiral galaxy.
Scientists are investigating whether the high supernova rate is a coincidence or a result of the merger.
The Swift study was led by Pennsylvania State University, US.
The observatory is a US space agency-managed mission with a big British and Italian contribution.
The UK's major input has been to provide an X-ray camera and elements of the UltraViolet/Optical Telescope.