A couple of “nu” stars trot along with the Dog Star, Sirius, in Canis Major, the big dog. Both stars are actually old — they’ve entered one of the final stages of life. The “nu” comes from their names — Nu-2 and Nu-3 Canis Majoris. The word is n-u — the 13th letter of the Greek alphabet.

Nu-2 is a single star that’s the same age as the Sun — 4.6 billion years. But it’s about 30 percent heavier than the Sun. The extra mass revved up the nuclear reactions in its core, so the star has puffed up to become a giant.

The star has two known planets. Both are big and heavy, and not likely to harbor life. But if they have moons, it’s possible they could sustain life. As Nu-2 puffed up, though, it got a lot brighter. Since both of the planets are close to the star, the extra energy could be bad news for any life there.

Nu-3 consists of two stars. The main star is about three-and-a-half times the mass of the Sun. So even though it’s less than 400 million years old, it’s already moved into the giant phase of life. It’s so big that it’s 400 times brighter than the Sun, so it’s visible even though it’s more than 400 light-years away.

Sirius is in the southeast in early evening. It’s the brightest star in the night sky. Nu-2 and -3 are off to its right. They’re much fainter than Sirius, so you need fairly dark skies to see them. And in case you’re wondering, there’s also a Nu-1, but it’s so faint that you need really dark skies to see it.
 

Script by Damond Benningfield