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The brightest star of Orion stands due south at nightfall, marking one of the hunter’s feet. Rigel shines blue-white — a dramatic contrast to orange Betelgeuse, Orion’s second-brightest light.

Both stars are supergiants — stars that are among the biggest and heaviest in the galaxy. Rigel, for example, is up to a couple of dozen times the mass of the Sun, and perhaps 70 times the Sun’s diameter. But the different colors tell us that the surface temperatures of Rigel and Betelgeuse are quite different. Betelgeuse is much cooler than the Sun, while Rigel is thousands of degrees hotter.

That may be an indication that they’re in different phases. Both stars are destined to end their lives as supernovas — powerful explosions that leave only dense, crushed cores.

But it’s still not clear how that plays out. Astronomers aren’t sure if a supergiant first becomes red, then evolves to a blue phase, or does things in the opposite order, or oscillates between phases. It’s also possible that some supergiants explode while they’re red, while others go out while they’re blue. Either way, both stars are doomed.

Bright blue Rigel is more than 850 light-years away. That’s a long way for a star that’s visible to the eye alone — and especially for one that bright. It’s such a beacon because it’s hundreds of thousands of times brighter than the Sun — a big, hot, bright blue star with a brighter future.

Script by Damond Benningfield

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