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Fuzzies in Your Future:An Introduction to Deep-Sky Objects
First of all, the Milky Way features not just countless stars but hundreds of eye-catching open clusters. Each open cluster is a gravitationally bound clan of anywhere from several dozen to several hundred stars. These clusters span a wide range of ages, but typically they are no more than a few hundred million years old — mere toddlers compared to our 4.6-billion-year-old adult Sun. Many open clusters are comparatively large and bright. Binoculars are excellent for spotting them against the celestial background.
A splendid example is Messier 35 (M35). Located 2,800 light-years away in the constellation Gemini, M35 contains about 200 suns. In 7×50 binoculars, you might count half a dozen stars sprinkled against a coarsely textured haze spanning nearly a half degree (nearly the apparent size of the full Moon). Viewed through a telescope at low magnification, M35 fills the eyepiece field with curving chains of stars.
Globular clusters are quite different. Our galaxy's halo is dotted with about 150 globulars, each a dense ball of several hundred thousand stars. And get this: their stars are 12 to 13 billion years old, making the globular clusters the senior citizens of the Milky Way.
One of the finest globulars in the northern heavens — and certainly the easiest to track down — is Messier 13 (M13), the Great Cluster in Hercules. Some 21,000 light-years distant, M13 shows up in binoculars as a faint, out-of-focus "star." However, a 6- or 8-inch (150- to 200-mm) telescope used at moderately high magnification (100× or 150×) can resolve the blur into a hive of glowing dots.
