Glowing clouds of gas and dust surround the three stars of Orion's Belt in this long-exposure photograph of the region. From left, the stars of the belt are Alnitak, Alnilam, and Mintaka. All three are supergiant stars that will explode as supernovae. The nebulosity around the stars includes the Horsehead Nebula, a dark notch in the red cloud close to the lower left of Alnitak. [Rogelio Bernal Andreo/Wikimedia]
You are here
Being a member of a popular group can make you famous — just not as yourself. Consider three stars at the center of Orion the hunter. They’re some of the biggest, brightest stars in the galaxy. Yet almost no one pays attention to them as individuals. Instead, we think of them as a group: Orion’s Belt.
Orion is in the eastern sky at nightfall. The belt points straight up from the horizon, with Orion’s other bright stars arrayed to its left and right.
From top to bottom, the stars of the belt are Mintaka, Alnilam, and Alnitak. The names are from ancient Arabic. Mintaka and Alnitak refer to the “Belt of the Great One” — a giant figure whose origin is unknown. Alnilam refers to an alternate name for the belt — the “string of pearls.”
There’s no doubt that these stars are among the most impressive jewels in the entire Milky Way.
Alnitak is a binary. It consists of two supergiant stars, which are much bigger and heavier than the Sun, and tens of thousands of times brighter. And Mintaka appears to consist of at least four stars, all of which are among the biggest and brightest in the galaxy.
The stars in the Belt are all much younger than the Sun — only a few million years old, compared to a few billion years for the Sun. Even so, they’re closer to the ends of their lives. They’re burning through their nuclear fuel in a hurry, and will expire soon — perhaps by blasting themselves to bits.
We’ll talk about an Orion’s Belt here on Earth tomorrow.
Script by Damond Benningfield