Astronomers look into heart of exploding star

An international team of astronomers has been able to see into the heart of an exploding star, revealing how gamma-ray emissions are produced -  something which mystified astronomers when they were first observed in 2012.

Because this type of ejection is also seen in binary star (two stars orbiting each other) systems, the new insights may help astronomers understand how those systems develop.

"We not only found where the gamma-rays came from but also got a look at a previously unseen scenario that may be common in other nova explosions," said Laura Chomiuk from the Michigan State University in the US.

They combined data from telescopes that are hundreds or even thousands of kilometres apart.

Highly-detailed images produced using radio telescopes from across Europe and America have pinpointed the locations where a stellar explosion (called a nova), emitted gamma-rays (extremely high-energy radiation).

A nova occurs when gas from a companion star falls onto the surface of a white dwarf star in a binary system.

This triggers a thermonuclear explosion on the surface of the star which blasts the gas into space at speeds of millions of miles per hour.

When it explodes it brightens hugely, leading in some cases to the appearance of a new star in the sky, hence the term nova. Astronomers did not expect this nova scenario to produce high-energy gamma rays.

However, in 2012, NASA's Fermi spacecraft detected gamma-rays coming from a nova called V959 Mon, some 6500 light-years away from Earth.

Later observations revealed two distinct knots of radio emission. These knots then were seen to move away from each other.

This observation allowed scientists to put together a picture of how the radio knots and the gamma rays were produced.

"Now, we may be able to use novae as a 'testbed' for improving our understanding of this critical stage of binary evolution," researchers concluded.The results were published in the journal Nature.