Astronomer snaps ‘one in 100 million’ shot of massive exploding star

22 Feb 2018

Image: Igor Zh./Shutterstock

When you consider the scale of the universe, one astronomer’s lucky snapshot of a massive exploding star was achieved under ‘astronomical’ odds.

On 20 September 2016, amateur astronomer Víctor Buso had just bought a new camera for his telescope and wanted to test it, so he pointed it at a particular spot in the distant universe to see what the images looked like.

Little did the Argentinian man know at first that he had captured an image that so many full-time astronomers failed to: the first light of a massive exploding star.

The images were of the spiral galaxy NGC 613 located 80m light years from Earth, and showed the before and after of the supernova’s ‘shock breakout’.

This is when a supersonic pressure wave from the exploding core of the star hits and heats gas at the star’s surface to a very high temperature, causing it to emit light and rapidly brighten.

Buso immediately examined the images after he took them and realised what he had photographed, noticing a faint point of light quickly brightening near the end of a spiral arm that was not visible in his first set of images.

Passing on the images to an Argentinian observatory, astronomer Melina Bersten and her colleagues realised the huge scientific importance of this discovery, estimating the chances of Buso capturing these images being as high as 100 million to one.


Sequence of combined images (negatives, so black corresponds to bright) as SN 2016gkg appears and brightens in the outskirts of the spiral galaxy NGC 613. Image: Víctor Buso

‘Like winning the cosmic lottery’

Because of its importance, the data was shared among the global astronomical community, leading to a team from the University of California, Berkeley, analysing the data in great detail, with its findings published in Nature.

“Professional astronomers have long been searching for such an event,” said UC Berkeley astronomer Alex Filippenko. “Observations of stars in the first moments they begin exploding provide information that cannot be directly obtained in any other way. It’s like winning the cosmic lottery.”

Filippenko and his colleagues obtained a series of seven spectra, where the light is broken up into its component colours, like in a rainbow.

This allowed the international team to determine that the explosion was a Type IIb supernova, a massive exploding star that had previously lost most of its hydrogen envelope.

Estimates put this particular supernova as having the initial mass of 20 suns, slimming down to around five solar masses prior to exploding.

Colm Gorey was a senior journalist with Silicon Republic