Brightest supernova discovery hints at stellar collision - space - 03 January 2007 - New Scientist Space

A supernova intrinsically two to three times brighter than any
previously recorded has been observed, and its characteristics suggest
it did not form like others of its class.

It appears to have been forged in a collision between two stars, adding
fuel to a long-running debate about what causes the type Ia explosions
that are a crucial tool in cosmology.

The prevailing view of type Ia supernovae is that they result from a
dense stellar corpse called a white dwarf that slowly collects matter
from an ordinary companion star. Eventually the white dwarf reaches a
mass threshold called the Chandrasekhar limit, triggering an explosion
that completely destroys it.

Much more at http://space.newscientist.com/article.ns?id=dn10883