Original URL: http://www.theregister.co.uk/2012/03/21/nasa_swift_supernova_findings/

'Now we understand what's required to explode a supernova' - NASA

Fortunately it isn't anything we've got lying about

By Lewis Page

Posted in Science, 21st March 2012 09:22 GMT

Top space boffins say that the latest readings from an orbiting science instrument have unlocked the secrets of mighty "Type Ia" supernovae, events in which stars blow up with such violence that they destroy solar systems and outshine entire galaxies.

The new data come from NASA's Swift satellite, orbiting the Earth and sending back observations of short-wavelength radiation from Type Ia super-mega-explosions afar off in the deeps of space.

“Now, thanks to unprecedented X-ray and ultraviolet data from Swift, we have a clearer picture of what’s required to blow up these stars," says Stefan Immler, NASA astrophysicist involved in the research.

It's well known among astro-boffins that Type Ia supernovae originate with a remnant star called a white dwarf, which detonates when pushed to a critical mass. Just what's required to happen in the run up to the explosion, however, has been harder to pin down.

Two main scenarios had been considered possible: in one, the white dwarf sucks in and gobbles up matter from a companion normal star, so gaining mass until, overstuffed, it blows up with unimaginable violence. Alternatively, two white dwarfs might collide like vast hypermassive billiard balls leading to a cataclysmic blast.

In between sniffing gamma-ray bursts emitted from faraway black holes (its main task) Swift has been used to probe Ia supernovae. In two separate studies, featuring 60-odd of the superviolent blasts, boffins couldn't find any of the types of X-ray or ultraviolet emissions which would indicate that a giant star had been present at the explosion site - the immolation of such a vast star would cause a noticeable amount of these wavelengths to be produced.

Thus, the scientists conclude, if a companion star is present when Type Ia supernovae kick off, it is generally smaller than our own Sun - indeed, these results could suggest that the dwarf-conkers theory is actually the correct one.

Studies based on the data are set to be published in prestigious astroboffinry journals The Astrophysical Journal Letters and The Astrophysical Journal in April. They can be read in advance of press here and here. ®