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December 4, 2022

Rigel — the brightest star of Orion the hunter — is complicated. It’s going through some changes in its core that will make it much bigger and brighter. Its surface jiggles like a Jell-O mold. And it’s blowing a “wind” of hot gas into space — enough material every million years to make one or two stars as big as the Sun.

All of this activity is a result of Rigel’s great heft — more than 20 times the mass of the Sun. Such heavy stars burn through the nuclear fuel in their cores in a hurry, so their lives are short. Rigel is only a fraction of one percent of the age of the Sun, yet it’s already nearing the end of its life.

The star has consumed the hydrogen in its core to make helium. The core is now shrinking and getting hotter — perhaps hot enough to start burning the helium.

Nuclear reactions are taking place in a shell of hydrogen around the core. Some models say that makes the surface jiggle, with each jiggle lasting anywhere from a day to more than two months. But other models say the jiggles are created at the surface of the star.

That surface is extremely hot, so Rigel glows blue white. When the helium in the core ignites, though, the star’s outer layers will expand and cool, so Rigel probably will glow reddish orange.

All of that is a prelude to its final act: In the next few million years, Rigel will explode as a supernova.

Look for Rigel low in the east-southeast by about eight o’clock, to the right of Orion’s Belt.

Script by Damond Benningfield

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