You are here

Deep-Sky Object of the Week: M3

As spring in the Northern Hemisphere begins to blend into summer, the night sky changes as well: the huge galaxy-rich fields of early spring skies begin to drift down towards the west, and the objects closer to the Milky Way become more prominent. The late spring and early summer sky is full of an interesting type of object: globular clusters, huge balls of stars held together by their own gravity, orbiting the entire Milky Way galaxy.

One of the first globular clusters to appear in spring is M3, third in Charles Messier's famous catalog of deep-sky objects. M3 is in Canes Venatici,the Hunting Dogs that perpetually chase Ursa Major around the sky. Like many of the spring Messier objects, M3 is in a fairly empty part of the sky. It has a magnitude of +6.2, making it just visible without a telescope under a dark sky. Observing details follow...

Observing globular clusters is often quite easy. They're generally bright, so you can find them in your finder (or sometimes, under dark skies, without a telescope at all). Globular clusters are one type of object you can observe quite nicely from a city, or on nights where there's significant moonlight. Unlike nebulas and galaxies, stars become significantly more visible at high magnification, since the high power dims the background skyglow without affecting the star much. As a result, you can see faint stars surprisingly easily from moderately light-polluted areas -- certainly much more easily than galaxies, nebulas, and comets.

I recently observed M 3 from my back yard with a small (100mm, or 4 inch, diameter) telescope. Even with local light pollution and some light from the rising full Moon, at high power (about 130x), there were a few stars visible in the edges of the cluster, and much of the cluster had a grainy appearance. The "grain" appears when the cluster is just short of being actually resolved. Telescopes in the 6 to 8 inch range will resolve many more stars, and begin to show the cluster's true nature. A 12-inch telescope will resolve it so completely that it'll resemble a photographic image.

If you live in the city, and you have anything but the very smallest of scopes, give a few globular clusters a try. You may be pleasantly surprised.

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer