You are here

Orion Rising

November 30, 2015

One of the icons of winter nights is climbing higher into the evening sky. Orion the hunter is in good view in the east by about 9 o’clock. Look for his “belt” of three moderately bright stars pointing straight up from the horizon. It’s flanked by orange Betelgeuse to the left and blue-white Rigel to the right.

All five of those stars — along with several of the constellation’s other bright gems — have something in common: They’re all supergiants. Such stars are much bigger and heavier than the Sun, and thousands of times brighter. And they share a common fate: They’ll end their lives with spectacular explosions.

The most impressive of Orion’s bright stars is Alnilam, the center star in Orion’s Belt. It’s about 40 times more massive than the Sun, and hundreds of thousands of times brighter. And it’s so big that if it took the Sun’s place in our own solar system, it would extend about half way out to the orbit of Mercury.

Such stars consume the nuclear fuel in their cores in a hurry, so they burn out quickly — millions of years, compared to billions of years for stars like the Sun. When the star’s time is up, its core collapses. Alnilam, for example, is likely to form a black hole. Its outer layers will then blast into space, creating a supernova. For a few weeks, it will shine as brightly as billions of normal stars — making Orion an even greater spectacle in Earth’s night skies.

Script by Damond Benningfield, Copyright 2015

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.