Do we need to worry about Betelgeuse exploding?

Far far away, the star Betelgeuse has done something strange. Could it be a sign that it's about to explode?...
11 November 2021

SUPERNOVA

A star becoming a supernova

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Question

Should we be worried about Betelgeuse exploding?

Answer

Thanks to astrophysicist and cosmologist Sarafina Nance, our fears about this cosmic issue were answered in this interview lead by Sally Le Page.

Sally - So Sarafina I first have to clear up, is it 'beetle-juice' or 'beetle-gurs?'

Sarafina - 'Beetle-juice'. You were right on the money the first time.

Sally - Good, and as far as I know, it's in Orion. That's pretty much all I know about it. Tell us more about it.

Sarafina - Yeah. It's the left shoulder of Orion and shines bright red. If you ever look up at the night sky and see the Orion constellation, you'll be able to spot Betelgeuse pretty easily because it's so red compared to the other white stars. It's red because it's a red super giant, meaning it's very, very, very big and it's later on in its stellar evolution lifecycle than our Sun, for example. So it has ballooned out and taken up this red colour and everybody, astronomers and non-astronomers alike, has been really interested in Betelgeuse, especially recently because it has been fading and dimming and people have wondered whether that dimming means that it might be close to exploding.

It's interesting because there's no real astronomical, physical reason why it should dim before it explodes. In reality, we would think that it would actually get brighter before it explodes, and that's what we've seen when we sort of look to other stars that have exploded. But that said, Betelgeuse is extremely close to us, it's about 600 light years away so we get a different perspective of the precursors or the progenitors of supernova, by watching and monitoring Betelgeuse than we see from other stars. That has tested our theories of stellar evolution to make us wonder if we understand exactly what goes on in a star before it explodes.

Sally - You say 600 light years isn't very far away. Does that mean I should be worrying, packing an emergency bag, something like that in case it goes off?

Sarafina - So the good news is... well there's two pieces of good news. The first is that it's probably not going to explode for another hundred thousand years. So even though it's going through this sort of dimming and rebrightening lifecycle, it turns out that that's actually because the surface of Betelgeuse is sort of expelling bits of dust. That dust is obfuscating the star from our line of sight and Betelgeuse simply appears dimmer than it actually is. I like to say that Betelgeuse has been 'burping' a lot and we are sort of not seeing it because we're seeing the 'burp' and not the star itself, so that's the first piece of good news. The second piece of good news is that it's far enough away that we will not really be impacted by the explosion. If we're still around in a hundred thousand years, we will simply see a very bright star that'll be as bright as the moon during the day and the night for about a month, and then it will sort of dim away. That's about as much of an impact as that explosion will have on earth.

John - How close is bad?

Sarafina - For example if our Sun were massive enough to explode as a supernova, it's not, that's not how it's going to die, but if it were we would be screwed.

Sally - So we're safe from the Sun? The Sun won't go supernova?

Sarafina - We're safe from the Sun. However, it will expand into being a red giant and similar to how Betelgeuse is red super giant, the sun will continue to expand in a similar fashion, and it will actually sort of envelop the Earth throughout its expansion. So that's not good news for us.

Sally - At least we might have wiped out all infectious diseases by that point, John though.

Sarafina - That's the bright side.
 

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