Orion's Belt

What it is

Orion’s Belt is the most famous asterism in the sky. An asterism is just a memorable pattern of stars, not one of the official constellations. Three stars of almost equal brightness sit here in a short, straight, evenly spaced line, a shape almost nothing else in the sky repeats. People have picked it out for as long as they have looked up.

A line only from here

Here is the honest part. The three belt stars are not neighbours. They sit at quite different distances from Earth and only appear to fall into a line from the one spot in space we happen to be standing on. The pattern is real, but it is a trick of perspective, a picture that exists only from our window. Connect the dots from anywhere else in the galaxy and the belt falls apart.

The three stars

From one end to the other they are Alnitak, Alnilam and Mintaka, all names from Arabic. Alnitak and Mintaka both mean roughly the belt or the girdle, and Alnilam comes from a word for a string of pearls. Plenty of cultures made their own picture from these three, from the Three Kings to the Three Sisters.

Your signpost to everything

The Belt is the key that unlocks the winter sky. Follow its line down and to the left and you reach Sirius, the brightest star. Follow it up and to the right and you reach the orange eye of Taurus the bull, Aldebaran. Just below the Belt hangs Orion’s sword, a short smudge of stars that holds the Orion Nebula, a glowing cloud where new stars are being born right now.