Triangulum

StarDate

Autumn’s evening skies offer some constellations with great names, intriguing back-stories, and beautiful star patterns. And then there’s Triangulum. As the name suggests, it consists of three main stars that form a triangle – an accurate if dull description of one of the smallest constellations.

The triangle looks like a thin wedge. And there’s an odd coincidence involving the stars at the base of the wedge: One of them is precisely third magnitude, while the other is precisely fourth magnitude. A lower number means a brighter star, so the third-magnitude star is the brighter of the two. Both stars are easily visible from dark skywatching sites, but more difficult targets from the city.

The brighter star is Beta Trianguli. It’s actually a binary – two stars bound together by gravity. The system is about 125 light-years from Earth. The other, Gamma Trianguli, is a little closer. The star at the tip of the wedge, Alpha Trianguli, is closer still. It’s in the process of swelling up to become a giant.

Perhaps the most impressive feature in Triangulum is M33, the Triangulum Galaxy. Through binoculars, it looks like a fuzzy star not far from Alpha. But that little smudge of light is a pinwheel of tens of billions of stars – three million light-years away.

Triangulum is in the east-northeast at nightfall. And this is a good time to look for it, because there’s no moonlight to overpower its faint stars.

Script by Damond Benningfield