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 email@example.com.