The death star: Astronomers catch final moments before supernova strikes

By Rob Waugh

In summer this year, a fairly nondescript star system in the Whirpool galaxy suddenly caught astronomers' attention - it went supernova.

But scientists had already been watching - the researchers have been scanning 25 nearby galaxies for stars that brighten and dim in unusual ways, in order to catch a few that are about to meet their end.

They saw one star in this binary system dim noticeably before the other one exploded in a supernova - which might provide a 'litmus test' for predicting future explosions.

'There’ll be no supernova for our sun – it’ll just fizzle out,' Kochanek said. 'But that’s okay – you don’t want to live around an exciting star.'

The study, submitted in a paper to the Astrophysical Journal, provides the latest result from an Ohio State University galaxy survey underway with the Large Binocular Telescope, located in Arizona.

In the first survey of its kind, the researchers have been scanning 25 nearby galaxies for stars that brighten and dim in unusual ways, in order to catch a few that are about to meet their end.

In the three years since the study began, this particular unnamed binary system in the Whirlpool Galaxy was the first among the stars they’ve cataloged to produce a supernova.

Though they’re still sorting through the data, it’s likely that they didn’t get any direct observations of the star that exploded – only its much brighter partner.

Yet, principal investigator Christopher Kochanek, professor of astronomy at Ohio State and the Ohio Eminent Scholar in Observational Cosmology, does not regard this first result as a disappointment. Rather, it’s a proof of concept.

'Our underlying goal is to look for any kind of signature behavior that will enable us to identify stars before they explode,' he said. 'It’s a speculative goal at this point, but at least now we know that it’s possible.'

A handout artist illustration of a supernova: The new research hopes to identify 'warning signs' - and eventually a 'litmus test' for stars that are about to explode

'Maybe stars give off a clear signal of impending doom, maybe they don’t,' said study co-author Krzystof Stanek, professor of astronomy at Ohio State, “But we’ll learn something new about dying stars no matter the outcome.'

Postdoctoral researcher Dorota Szczygiel, who led the study of this supernova, explained why the galaxy survey is important.

“The odds are extremely low that we would just happen to be observing a star for several years before it went supernova. We would have to be extremely lucky,” she said.

'With this galaxy survey, we’re making our own luck. We’re studying all the variable stars in 25 galaxies, so that when one of them happens go supernova, we’ve already compiled data on it.'

As astronomers gather data from more supernovae – Kochanek speculates that as many as one per year could emerge from their data set – they could assemble a kind of litmus test to predict whether a particular star is near death.
The team won’t be watching our sun for any changes, however. At less than 10 percent of the mass of the star in supernova 2011dh, our star will most likely meet a very boring end.

'There’ll be no supernova for our sun – it’ll just fizzle out,' Kochanek said. 'But that’s okay – you don’t want to live around an exciting star.'

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