Mysteries surrounding the brightest supernova explained
02 Jan 2008
Astronomers at the University of Amsterdam have found an explanation for the peculiarities which characterise the bright supernova which has been visible since 18 September 2006.
Supernova SN2006gy was not only the brightest ever observed, but also generated an exceptionally high concentration of hydrogen in the shockwave which followed the gigantic explosion, despite this never having happened before with this type of supernova. Prof. Ed van den Heuvel and Dr Simon Portegies Zwart attribute this to the unique development of the star which exploded at the end of its life, forming the supernova. They published their findings in Nature on 15 November.
The astronomers calculated that the heavy precursor star must be the result of a stellar collision in a dense, young cluster of stars with a large number of heavy stars. The result of a collision like this is not an explosion but the merging of the two stars to form a new one. This ‘fusion result’ has a number of special properties, including a profusion of hydrogen on the surface of van the merged star. “Star collisions are a very efficient way of ensuring that large quantities of fresh hydrogen fall onto the burning internal ‘motor’ of a heavy star,” explains Spinoza prize winner Ed Van den Heuvel. As soon as the heavy star explodes, the hydrogen is released into the supernova.
According to Simon Portegies Zwart, the supernova must have created a heavy black hole, with possibly around 1,000 times more mass than the sun. This category of medium-heavy black holes is very rare and their existence has, to date, only been demonstrated indirectly. Portegies Zwart and Van den Heuvel predict that, in about a year, when the supernova has faded, it will be possible to see the cluster of stars in which the collisions occurred which eventually led to SN2006gy.
The research was supported by the Netherlands Organisation for Scientific Research (NWO) and the Netherlands Research School for Astronomy (NOVA).