Messier 37

A 500 million-year-old star cluster climbs high overhead during late fall and winter. It’s not quite visible to the unaided eye, but it’s a fairly easy target for binoculars.

Messier 37 probably is about 5,000 light-years away, and it contains about 500 known stars. And it could have even more stars, but they’ve been too faint, or too far from the cluster’s packed center, for astronomers to pick them out.

We know the cluster’s age because of its population of stars. When a cluster like M37 forms, it has a mixture of stars of all sizes and masses.

M37 is basically bereft of the two heaviest classes of stars, which burn out quickly. But it has quite a few of the next class, which last longer.

Since we know how long it takes all of those stars to expire, we have a pretty good idea of the cluster’s age: Longer than the lifespans of the heaviest stars, but shorter than the spans of medium-mass stars. When you plug in all the numbers, it works out to about half a billion years — barely more than one-tenth/the age of the Sun.

Auriga is in the east-northeast as darkness falls. It consists of a pentagon of stars, with brilliant Capella at its top left point. M37 is a little below the figure. In modest binoculars, it looks like a fuzzy star. Higher-power binoculars, though, reveal many of the cluster’s individual stars — a family of stars that’s still quite young.

Tomorrow: looking for signs of life.

Script by Damond Benningfield