SN 2002bj was the explosion of a star in the galaxy NGC 1821, located in the constellation Lepus.[1] The explosion was discovered by Jack Newton in scans of images produced by Tim Puckett. (It was independently discovered by the Lick/Tenagra Observatory as part of their combined supernova search program.) Initially it had an apparent magnitude of about 14.7[2] and was categorized as a Type IIn supernova.[3] However, in 2008 Dovi Poznanski discovered that the spectrum more closely resembled a Type Ia supernova. Further, the energy output was much lower than a typical supernova and the luminosity dropped at a dramatic pace.[4] A team consisting of Poznanski, Joshua Bloom, Alex Filippenko and others concluded that it was a new category of exploding star. This system is believed to consist of a binary pair of white dwarf stars, with helium being transferred from one dwarf to the other. The accreted helium exploded in a thermonuclear reaction on the surface of the more massive white dwarf, resulting in the observed outburst.[4] In this sense, it was akin to a nova explosion, although the magnitude of the explosion was a thousand times greater.[1] In 2007, Lars Bildsten et al.. had predicted this category of explosion would occur in AM Canum Venaticorum-type binary systems.[5] NGC 1821 is an irregular galaxy categorized as type IB(s)m. It is apparent magnitude 14.5 and has a redshift of 0.012029. This galaxy is located about 48 megaparsecs from the Earth.[6] References ^ a b Sanders, Robert. "Rapid supernova could be new class of exploding star". UC Newsroom (University of California, Berkeley). Retrieved 2009-11-06.
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