On clear nights I make a point of looking for Betelgeuse – Alpha Orionis, an M2Iab class red supergiant. It’s the bright red star in Orion, below the belt from the New Zealand perspective.
It’s naked-eye bright – magnitude 0.42, which is duller than it was in the 1930s but still one of the top eight brightest stars in the sky besides the Sun. And it’s gonna blow – as in, explode as a Type II Supernova. Not today. Maybe tomorrow. Maybe not for a million years.
But blow it will. Vlabadaboom! Actually, given that Betelgeuse’s distance was recently revised to 425 light years (about 4,020,724,570,000,000 kilometres) it could have blown any time after 1588 and we wouldn’t know yet. Not until the light hits us. It’s too far off to be any threat – but it’ll be bright, it’ll be spectacular, and we’ll have a second sun for a while. Here’s a simulation on YouTube.
Why will it go bang? Stars shine by fusing hydrogen into helium. When hydrogen near the core runs out, the star fuses helium into lithium, and so on up the Periodic Table. Each element fuses at higher temperatures, causing the star’s outer layers to puff up, turning the star into a red supergiant.
That’s what Betelgeuse is, and if you were to look at its surface you’d see it roiling and boiling under the ferment at its core. The star also waxes and wanes, vigorously – it’s a Type SRc variable.
For Betelgeuse, life as a red supergiant is a one-way journey. Once the core starts turning silicon into nickel, which decays into iron, that’s the end. At that point, the core cools and is buoyed from gravitationally collapsing on itself by a curious outcome of quantum physics – electrons cannot be forced into the same energy states. But once the core exceeds a mass of 2.864 × 10<exp>30 kg, known as Chandrashekar’s Limit, it collapses in milliseconds. Lots of interesting extreme physics things happen, leading to one thing – vlabadaboom!
We don’t know exactly when this will happen, but I calculated that the odds of my seeing Betelgeuse explode during a five second glance are, statistically, about the same as anybody winning New Zealand’s lottery prize.
What’s more, Betelgeuse is pretty neat to look at. It’s got a diameter 1500 times that of the Sun – so if its centre was where our Sun’s centre is, the edge of its photosphere would be most of the way to Uranus. (Don’t laugh.) Sure, that makes most of the star a good simulation of high temperature vacuum – it’s 20 times the mass of the Sun, making the average density about 1/10,000th that of sea-level air pressure on Earth. But it’s still mind-boggling. At 0.05 arc-seconds, you can’t see the disk with the naked eye, but you can see the colour, and that’s unusual.
So I figure Betelgeuse is pretty cool and interesting all round – and, maybe, it might explode while I’m looking at it. Maybe.
Copyright © Matthew Wright 2013
Next week…secrets of Eta Carinae and how it might blitz Earth. Seriously – this is genuine science. And yes, you need to know.
I’m also a huge fan of Betelgeuse – it even features heavily in my own novel: ‘The Foretelling: A Journey to Truth’. It’s fascinating to consider the immensity of some of the objects in the night sky – here’s a 2 min video that puts things in perspective: http://www.youtube.com/watch?v=58fs5yI8K9I
And it does, indeed! I suspect we cannot really comprehend the actual scales of the universe – they are massively far beyond our human world. We only think we can.
I am so hoping this happens in our lifetime, though it would be sad not to see it anymore when I look into the sky during summer. But to witness a supernova? There are very few moments in recorded history where people have had that opportunity.
It would be fantastic to see in our lifetimes indeed. We’d join the ranks of Tycho Brahe and those Chinese astronomers who watched the one that made the Crab Nebula (now a pulsar, I think). Certainly it’d be sad not to have Betelgeuse any more, but imagine the cool science that would follow as we watched the nebula expand.
I expect you’ve seen that comparison of Earth to the Sun compared to Antares compared to Betelgeuse, etc. It’s positively mind boggling. I wish the leaders of all the nations on Earth would have a look at that. I mean really think about that, and realize how insignificant our petty little turf wars are. Okay, I see the poster above me has something like I was thinking of.
Recently, I saw something on the Science channel and scientists were saying if you want to kill a star, just plug Iron at it’s center. Once iron forms in a star’s core, it will go nova. Fascinating stuff.
Yes I have – it’s pretty humbling to think about the scales and the perspective it puts our mere human activities into. I think the Pistol Star was top-ranked on that particular list – spews out as much energy in 20 seconds as the Sun in a year, and that’s without blowing up… 🙂
THis takes the term “Going out with a BANG” to a whole new level! I wouldn’t want to miss this for the World!
Sure does! And me neither…
You always have cool info. Thanks.
Thanks…weirdly, in Betelgeuse’s case, it IS cool, literally, for a star…that’s Betelgeuse’s problem… 🙂
Wow! I had no idea it would look like that when it exploded. That’s fascinating. Thanks for sharing.
It’s a scientific best guess anyway – and I think we can be sure it’ll be visible in daylight even if it’s a bit dimmer than estimated.