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zeeblecroid t1_j25oyry wrote

Zero - it's not burning the right elements to be near that point yet.

Stars on the road to supernovas go through a sequence of burning increasingly heavy elements for increasingly short periods of time, and Betelgeuse is still in the helium-burning phase. The following phases burn carbon, neon, oxygen and silicon in order, and once a star starts gnawing on its helium that gives observers about one thousand years' warning. Betelgeuse is 600-ish lightyears out; if it was most of the way through that process we'd be able to tell.

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tempejkl OP t1_j25uga4 wrote

I know about this, but can we see what elements a star that far away is burning? How does that work?

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Pleasant_Carpenter37 t1_j25w2gb wrote

You know how fireworks flash different colors? We put different things in the fireworks to make different colors. Aluminum burns white, barium burns green, etc.

The same thing is true in stars. We basically look at the light coming from a star, count up the mixture of colors we see, do some complicated math, and that gives us an estimate of what it's doing.

If you want more detail than my crude eli5 can give you, read up on spectroscopy.

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AncientMarinerCVN65 t1_j25sp5j wrote

That's how I understand it, as well. And when it does go Supernova, it's too far away to do serious damage to Earth. It will give off enough light to be as bright as a half moon for about a month. It will even be visible during daylight, but the blast wave will dissipate to almost nothing by the time it reaches us. We'll just have really nice aurorae for a few years as the stellar remains wash over our Solar System (centuries after we see the Supernova itself, since what's left of the star will be traveling below the speed of light).

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