M35, This Month’s Most Beautiful Star Cluster

A superb object for small telescopes, the open star cluster Messier 35 in Gemini ranks as one of the most beautiful objects in the heavens. Even a modest scope reveals curved strands of stars twisting about a sparse central region, like bursting fireworks on a dark summer night.

The Basics

• Messier 35 should top your list of things to see this month. No matter how often you observe this fine cluster, you will see new patterns and shapes in the interwined strands woven among this young cluster’s 300 stellar members.

• In binoculars, M35 looks like a tiny patch of frosted silver, with a few stars visible at most. In a 3-4-inch telescope you’ll see 40-50 stars, with more revealing themselves upon careful examination. In a 8-10-inch scope, the view of this cluster is awesome, with bright blue and white stars blazing in the field of view, along with a few red giants evolving off the main sequence.

• Unlike many star clusters, M35 has no central condensation. In fact, many observers see an absence of stars or a “hole” near the center of the cluster, which, with a little imagination, gives it the appearance of a sparkling sugar donut.

Deeper Look

• M35 is barely visible to the naked eye in clear dark sky. And at magnitude 5.1, it appears quite faint because it’s spread out over an area of sky as large as the full Moon, just like the faint galaxy M33.

• To find M35, look just a couple degrees northwest of the star eta Geminorum, one of the feet of the constellation Gemini, the Twins. It’s coordinates are RA 6h09m, Dec +24d21m. The cluster is visible in the north and most of the southern hemisphere.

Messier 35 (right side of map) in Gemini

• The particulars: M35 is some 2,800 light years away, and spans a diameter of 30 light years. Like most open clusters, M35 is younger than most of the rocks in your back yard: it formed only 50 million years ago.

Bonus Object

Within the same field of view as M35, about 0.5 degrees to the southwest, you may see a much smaller open cluster. NGC 2158 is about the same size as M35 in real terms, but it appears smaller because it’s 6x farther away. In a 4-6 inch scope, you will need dark sky and averted vision to spot this tiny cluster. Even with a larger telescope, dark sky is essential: I’ve always had trouble seeing this one from the city.

Personal View

For the past couple of years, on the rare winter night when it’s not cloudy or freezing cold here, I’ve been hopping the open clusters of Cassiopeia. So I’d almost forgotten the splendor of M35. I examined it again before writing this article. This is an achingly beautiful star cluster… I urge you to see it for yourself.