Monday, July 22

‘Once-in-a-lifetime event’: rare chance to see explosion on dwarf star 3,000 light years away | Astronomy

In what is being called a “once-in-a-lifetime event”, light from a thermonuclear explosion on a star has been travelling towards Earth for thousands of years and it will be here any day.

T Coronae Borealis (also known as T Cor Bor, T CrB, and the Blaze star) will be as bright as the north star (for those in the northern hemisphere).

Dr Laura Driessen, from the University of Sydney’s school of physics, said the Blaze star would be as bright as Orion’s right foot for those in the southern hemisphere.

A recurrent nova, T CrB becomes visible about every 80 years after a thermonuclear explosion on the surface of a white dwarf about 3,000 light years away.

The dwarf sucks up hydrogen from a neighbouring red giant, and that causes a buildup of pressure and heat that eventually triggers the explosion.

Known as a nova (for “new”), it is expected to become visible anytime from now until September.

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In the Corona Borealis, there is a dark spot. Astronomers and non-astronomers everywhere are monitoring that spot, which is where the “new” star will appear. It will stay visible to the naked eye for about a week.

Nasa has called it a “once-in-a-lifetime event”.

Driessen said the two stars are close enough that a gravitational pull results in the white dwarf sucking in material. “It’s a binary system and every now and then it has an outburst, so it’s a nova,” she said.

“When we think nova we often think supernova, which is when they explode at the end of their life … there’s no coming back from that. But a nova has smaller surface explosion, based on this accretion, this gathering of material.”

The first recorded sighting of the Blaze star was in 1217, when the abbot of Ursberg, in Germany, saw “a faint star that for a time shone with great light”, Nasa says.

It was last seen in 1946.

Driessen said the star is always variable, getting brighter and fainter. But about 10 years before an explosion it starts to get a bit brighter, before fading again in the months before the explosion.

“It’s not really going to be like clockwork, it’s to do with the buildup of material. So it’s not an exact number but we’ve got this early warning.”

While the spectacular phenomenon has been observed before, Driessen said this was the first time it could be studied with modern technology.

“That’s why it’s so exciting. It’ll be the first one where we get the information we can access now, we have all these telescopes we didn’t have 80 years ago.”

Nasa’s Fermi Gamma-ray Space Telescope, the James Webb Space Telescope, and the National Radio Astronomy Observatory’s Very Large Array in New Mexico are just some of the instruments that will track the Blaze.

The Fermi project scientist Dr Elizabeth Hays, who is also chief of Nasa’s Astroparticle Physics Laboratory, said typical nova events were far away.

“This one will be really close, with a lot of eyes on it, studying the various wavelengths and hopefully giving us data to start unlocking the structure and specific processes involved,” she said. “We can’t wait to get the full picture of what’s going on.”

Nasa has a map of the Corona Borealis to help people pinpoint where to look, and Driessen said software such as Stellarium was also useful. There are several free apps to view maps of the night sky.

Driessen said people should find the darkest area they can, as far away from a city or town as possible, and take binoculars for an better view.

“Let your eyes adjust for the dark,” she said. “And it’s good to have a red torch. Put a bit of cellophane over it, so it doesn’t ruin your night vision. And don’t look at your phone.”

source: www.theguardian.com