M 35

M35 (NGC 2168)


M35 is an open star cluster of over a hundred stars, easily seen in small telescopes or binoculars. Even the naked eye can pick it out on a clear night.

In binoculars mu, eta, and M35 are in the same field of view. At the right edge of your glasses is the bright 1 Geminorum, combined 4.2 visual magnitude (the star is a very close binary). The cluster is just to the northeast.

This is a fine binocular object (even better in small telescopes) that spreads out to cover an area slightly larger than the full moon. There are perhaps two dozen bright stars that can be resolved in 10x50s. The cluster is 2500 light years away and is from sixty to seventy million years old.

A half-degree to the southwest of M35 is the much older open cluster NGC 2158. Since it was formed at least a billion years age it has no bright blue giants, which are typical of younger clusters. Instead there are red giants here. But don't be disappointed if you can't see the cluster; it's completely invisible in 7x50s and one needs very sharp eyes and perfect conditions even with 10x50s just to distinguish a very small point of light. Not surprising, for the cluster is 15,000 light years away! If you have access to a large telescope, you might note this object for future study.

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1999-2014 by Richard Dibon-Smith.