SN2007on is a type Ia supernova that is useful in measuring the acceleration in the expansion of the Universe. These supernova types have been found to be the product of an explosion of a white dwarf in a binary star system and are responsible for most of the iron ever created in the universe. Discovered in November 2007 by the 10-inch TAROT robot telescope at La Silla in Chile, SN2007 is in a position in the sky where four years before no such supernova was found. SN2007 is in the elliptical galaxy NGC 1404.

La Silla Observatory

This, with the aid of images taken in November and of archived images from four years ago, leads to the belief that before SN2007on appeared, a binary star system existed that was eventually destroyed in a supernova explosion. The explosion is theorized to either have occured due to a collision of the two binaries into each other or due to instability in the white dwarf caused by accretion of material off the sister star. If the latter, a strong emission of X-rays develops, caused by fusion and heat brought on by the accretion process, before the supernova explosion. This is referred to as the Chandrasekhar limit. The x-rays have been measured in the vicinity of SN2007 four years ago. After the explosion, the white dwarf vaporizes and the X-ray emissions cease. Observations by the Chandra X-ray observatory imply that the X-ray source has disappeared lending credibility to the ancestor hypothesis. Further research is required to confirm the X-rays were not from another source in the same area as the binary system.

Nature is publishing a technical article on this development here. However, to access the article one needs to be a subscriber. I’ve seen this journal at Barnes & Noble. It is $10 and published weekly. You can subscribe for the bargain price of $199 per year. Oh boy!

The archived images and more recent images of SN2007on can be found at the Chandra website at Harvard. They are quite interesting.