Nova explosion could give insight into where we come from

A red giant star and white dwarf orbit each other in this animation of a nova.

Star gazers are set for a treat any day now as a star system 3000 light years is on the verge of lighting up with a thermonuclear explosion.

A nova called T Coronae Borealis spectacularly erupts every 80 years, appearing as a new star in the sky.

It was first officially recorded in 1866 but could have been observed as far back as 1217.

University of Auckland head of physics professor Jan Eldridge told Nights in itself it was one little explosion, “but when you put it in the context of all the other stuff going on in the universe … we can always turn back and link into where do we come from, which is what we all really want to know, I guess”.

Eldridge’s research is focused on the lives and deaths of stars.

On a scale of one to 10, her excitement was at a 7.5 “because it is exciting, but it’s happened before”.

“But each time one of these novae explode, we can actually learn something quite new because they’re variable.

“So even though it’s so regular that it’s exploding every 80 years, why is there always a slightly different explosion? What’s happening in the system and evolving? So there’s always something to learn, and that’s pretty cool.”

She explained that novae were reoccurring, but with supernovae – which are a bit more explosive – there the entire star exploded.

The T Coronae Borealis was 1.37 times the mass of the sun, she said.

“And this is really close to something called the Chandrasekhar mass, where it might explode. And so actually if it keeps on getting bigger and bigger one day it would explode in a very bright supernova, which would be maybe as bright as the full moon rather than just as some of the faintest stars in the universe,” Eldridge said.

T Coronae Borealis

She said some novae increased or decreased in mass.

“The thing I love about this is when you’re modelling stars, you have to use every bit of physics there is because there’s so much you need to know about how atoms work, you have to know about gravity.

“You’re using modelling to create this entire picture. And of course, you can always understand and add extra things to your model because there are things we don’t understand. We have a huge amount of data now and there’s going to be even more in the future in trying to understand all of these objects.”

Why are people more excited about comets than novae?

“Comets are just much more spectacular,” Eldridge said.

“When you’re looking at a comet, you’re looking at a chunk of ice that’s going around our sun, and it’s really close, and it’s really extended.

“You see these different tails and they are spectacular and can be much bigger than the full moon. And they’re very easy to see with the naked eye.”

She said novae were difficult to see without a telescope.

Those who were savvy about the universe and stars would be excited about this nova explosion.

“This thing will be faint, it’ll be in the north, low to the horizon, depending on exactly which month it explodes into. We might not even be able to see it because of where we are,” she said.

When will it happen?

Eldridge said it could be somewhere within the next year.

“By looking at this system, we know how massive it is. We know how much hydrogen you need on the surface for it to ignite and you can work out how much is being transferred.”

If it exploded at some other time, it would mean a need to adjust the models, she said.

How to spot it?

While it would be faint at the start, it would be bright for those with telescopes.

Eldridge said there were phone apps that could direct where the nova might be.

“If you wanted to go and look at this star today, you would definitely need to use a telescope. And you have to really know where it is because you’d be searching amongst all these other very faint stars.

“But this is going to explode and it’s going to get something around about 10,000 times brighter and it will be naked eye visible, but you need to know where it is in the sky. Because if you look at the constellation, you’ll look at it and you’ll see the new star and that’s basically where the word novae comes from because it means new star.”

It would seen with the naked eye over a few days as it reached peak magnitude, she said.

“People will be studying it for weeks afterwards.”

It will be seen as a bright red giant star, with a hotter white dwarf.

“This thing ignites and you basically see a fireball coming off the surface of that white dwarf and that dominates the light that you then see from that system.”

As the fireball expands in size, it will eventually start to cool down and then fade away.

“And eventually that material, the ejector that’s been thrown off will cool down so much that then it’s the light from the stars which will be there underneath will still be seen.

“And that will be where it goes back to that brightness. Then you have to wait another 80 years for it to happen again.”

According to the news on Radio New Zealand

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