The Delaware Gazette

Do you really want to be a star?

Orion, the Hunter, dom­i­nates our win­ter nights. In Feb­ru­ary, you’ll find him almost due south around 8 p.m. His left shoul­der is marked by the red super­giant star called Betel­geuse, pro­nounced “beetle-juice,” a name that means “the armpit of the giant.” So if your loved ones ask you why you’re crazy enough to go out­side on these cold win­ter nights, just tell them you’re going to look at a giant’s armpit. That ought to give them pause.

Betel­geuse is more or less in our cos­mic neigh­bor­hood. At 540 light years (about 3.25 quadrillion miles) dis­tant, it’s close enough and large enough that the most pow­er­ful tele­scopes on Earth can actu­ally resolve it into a disk.

Betel­geuse shines about 12,000 times brighter than the sun. At per­haps 640 mil­lion miles in diam­e­ter, it makes our sun, which is only 865,000 miles wide, look like a speck. In fact, if we were to mag­i­cally replace the sun with Betel­geuse, it would extend well out beyond the orbit of Mars, and Earth would be deep inside the star.

Despite its enor­mous size, it prob­a­bly con­tains only 20 times more “starstuff,” mostly hydro­gen. As a result, the sun is mil­lions of times denser than Betel­geuse, which is only about 1/1,000 as dense as our Earth’s atmos­phere. In exper­i­men­tal sit­u­a­tions on Earth, it’s tough to cre­ate a vac­uum as insub­stan­tial as this dying star. If you hap­pened to be inside Betel­geuse you wouldn’t see any­thing at all.

Of course, you’d notice that you were inside. At 6,000 degrees Fahren­heit, Betel­geuse is lit­er­ally red hot, con­sid­er­ably cooler than our sun’s yellow-hot 10,000 degrees. In fact, stars like Betel­geuse are often described as “red-hot vac­u­ums.” To sum­ma­rize, Betel­geuse is prob­a­bly a lot like your aver­age pres­i­den­tial politi­cian — a hot, over­in­flated gas bag that’s short on substance.

How did poor Betel­geuse reach this sorry state? To answer that ques­tion, we must look at another star in Orion. The Hunter’s right foot is marked by the blue-giant star called Rigel, a very young star, per­haps only a few mil­lion years old. It has 30 times the starstuff of our sun, and is 62,000 times brighter.

Stars are enor­mous hydro­gen bombs, con­vert­ing their hydro­gen into helium and thus releas­ing light and heat. Most stars man­age to sus­tain this reac­tion for bil­lions of years.

By con­trast, Rigel is so hot and mas­sive that it burns its hydro­gen fuel at a much higher rate than the aver­age star. In a mere 100 mil­lion years or so (and maybe less), it will have used up most of its avail­able hydro­gen. It will then expand to enor­mous size and become a red super­giant like Betel­geuse, a bloated hulk of a star mil­lions of miles in diam­e­ter, old before its time.

But this is not the ulti­mate end for stars like Betel­geuse and Rigel. Even­tu­ally, the ther­monu­clear explo­sions in their cen­ters will cease, and the cores will rapidly col­lapse to tiny, mas­sive spheres. As the hot gasses at their outer edges col­lapse into even hot­ter cores, the stars will erupt in cat­a­clysmic explo­sions called supernovas.

Such is the force of these explo­sions that in their death throes Rigel and Betel­geuse will briefly shine with the bril­liance of 100 bil­lion stars. In their last, bright swan songs, they will out­shine the entire Milky Way galaxy of which they are but small parts.

Oh ye stargaz­ers, there is a life les­son in this. Such is the life of a prof­li­gate star — live fast, die young, and leave a beau­ti­ful super­nova. Per­son­ally, given the choice, I’d rather slog along like our very aver­age star, the sun, and shed my fee­ble light a good, long while.

Tom Burns is the direc­tor of Perkins Obser­va­tory. He can be reached at tlburns@owu.edu.

Tom Burns Posted by on Jan 27 2013. You can follow any responses to this entry through the RSS Feed. Comments can be made below.

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