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Brightest exploding stars spotted

Science | Space

Cath Harris | 09 Jun 11

Supernova

Scientists have identified a new type of supernova or exploding star which is ten times brighter than any other type of stellar explosion.

Astrophysicist Dr Mark Sullivan of Oxford University’s Department of Physics is among researchers reporting the discovery in this week's Nature.

Until now scientists have been aware of two basic types of supernova – ‘Type Ia supernovae’, which are thermonuclear explosions of small and very dense stars called white dwarfs – and slightly fainter ‘core collapse supernovae’, brought about by the deaths of very massive stars (possibly with masses up to 50-100 times that of the sun). This second type of supernova was featured in the BBC’s Wonders of the Universe.

The new research is published by 27 academics from Oxford, Caltech, the universities of California and Toronto, the Weizmann Institute and other leading institutions. 

It demonstrates the existence of a new, exceptionally bright, kind of supernova, 10 times more luminous than most Type Ia supernovae and with unique characteristics.

These new supernovae show no trace of hydrogen or helium, and emit significant ultraviolet flux for long periods, which means the exploding star was probably low in metals and from a very faint galaxy with few stars. Its light output decays in a way that suggests something other than radioactivity - which powers the light from all other supernova explosions - is the cause of its deterioration.

‘The mechanism of the explosion is unknown, which is the most exciting part,’ Dr Sullivan says. ‘The high luminosity means that these supernovae can be used to probe the very distant universe.’

Because the new supernovae are rare, it took a new type of search to find them - the Palomar Transient Factory [PTF]. The PTF is a systematic search for cosmic explosions and uses the Palomar Observatory in San Diego.

Oxford University is helping fund the project via the John Fell OUP Research Fund and the research is providing material for Galaxy Zoo Supernova [more here] which featured on the BBC’s Bang Goes the Theory.

‘Practically every chemical element in the universe (other than hydrogen and helium) gets made in stars,’ Dr Sullivan says. ‘This research has implications for both the study of stellar evolution and the way in which elements in the Universe were formed.’

Image: before (top three images) and after (bottom three images) images showing where the new ultra-bright supernovas have been identified.