The southern evening sky is pretty bare at this time of year – lots of dark, empty spaces, but few bright stars. The one notable exception is Fomalhaut. It’s the brightest star of Piscis Austrinus, the southern fish. It’s low in the southeast at nightfall, and arcs across the south later on.

The star we see as Fomalhaut is 25 light-years away. It’s about twice as big and heavy as the Sun, and more than 15 times brighter. It’s young – about 10 percent the age of the Sun. And it’s encircled by wide bands of dust, which may contain planets; more about that tomorrow.

Fomalhaut has two companion stars – bound to it by their mutual gravitational pull. Both stars are smaller, cooler, and fainter than the Sun. One of them is barely visible to the eye alone, but you need a telescope to see the other.

Both stars are a long way from Fomalhaut itself. One is almost a light-year away, while the other is two and a half light-years. Astronomers know they’re bound to Fomalhaut because they’re moving in the same direction and at the same speed. Their composition is similar to Fomalhaut’s as well, and so is their age.

Fomalhaut itself will shine for another few hundred million years. But the companions will last much longer – billions of years for the larger one, and hundreds of billions of years for the other. So they’ll still be shining across the galaxy long after the demise of their showy companion.

Script by Damond Benningfield