Astronomers may be learning to predict when a star is about to explodes tagged: , , , , , , ,

Astronomers may be learning to predict when a star is about to explodes

Posted by in Space

Courtesy of Ohio State University and World Science staff

New research may be helping astronomers learn what signals will predict a star is about to explode.

Many stars die explosively in events called supernovas, but scientists can’t currently predict when a star is about to meet that fate. This means they usually have to learn everything they know about these stars after they have already burst – depriving researchers of before-and-after data that would help explain the whole process.

Astronomers have therefore been scanning 25 nearby galaxies for stars that brighten and dim in unusual ways, hoping to catch a few that were about to meet an explosive end. In the three years since the work began, a double star system in the Whirlpool Galaxy has been first among the stars they’ve catalogued to yield a supernova.

The findings from the Ohio State University survey, carried out using Arizona’s Large Binocular Telescope, are detailed in a paper submitted to The Astrophysical Journal.

The astronomers were trying to find out if there are patterns of brightening or dimming that herald the end of a star’s life. Instead, they saw one star in this binary system dim noticeably before the other exploded in a supernova last summer.

If it works, they’ll use it

Although it was a surprise to realise you might have to watch one star to predict its partner’s death, the astronomers say whatever works, they’ll take it. The point ‘is to look for any kind of signature behaviour that will enable us to identify stars before they explode,’ said Ohio State astronomer Christopher Kochanek.

‘Maybe stars give off a clear signal of impending doom, maybe they don’t,’ added study co-author Krzystof Stanek, also an astronomer at Ohio State. ‘But we’ll learn something new about dying stars no matter the outcome.’

Dorota Szczygiel, a postdoctoral researcher at the university who led the study of the supernova, said ‘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.’

With the new survey, ‘we’re making our own luck,’ she added. ‘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.’ The supernova, labelled 2011dh, was first detected on May 31 and is still in a brightened state due to the explosion. The event took place in the Whirlpool Galaxy, also known as M51.

Binary stars are common

A binary star system is a common arrangement in which two stars are orbiting each other. This binary system is thought to have contained one very bright blue star and one even brighter red star. From what the astronomers can tell, the red star is apparently the one that dimmed over the three years, before the blue star initiated the supernova. When the researchers reviewed the Large Binocular Telescope data and Hubble Space Telescope images of M51, they saw that the red star had dimmed by about 10% over three years, at a pace of 3% per year.

Szczygiel believes the red star likely survived its partner’s supernova. ‘After the light from the explosion fades away, we should be able to see the companion that did not explode,’ she said.

As astronomers gather data from more supernovas – 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 given star is near death.

The team won’t be watching our sun for any changes, though. Since it’s less than one-tenth the weight of the star in supernova 2011dh, our star is predicted to meet a fairly boring, non-explosive end. ‘It’ll just fizzle out,’ Kochanek said. ‘But that’s okay – you don’t want to live around an exciting star.’

Image: This Large Binocular Telescope image of the Whirlpool Galaxy is part of a survey in which astronomers are searching for signs that stars are about to go supernova. The insets show one binary star system before (left) and after (right) one of its stars went supernova. (Image:  Szczygiel, courtesy OSU)

Source: World Science, http://www.world-science.net