A very dense ball of hundreds of thousands of stars, among the oldest in the Galaxy, orbiting its centre. M13 in Hercules, about 22,000 light-years away, is the finest in the northern sky. A 150 to 200 mm telescope starts to resolve it into stars.
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Related terms
- Open cluster
A group of a few dozen to a few thousand young stars, born together from the same gas cloud. The Pleiades (M45), about 440 light-years away, are the best-known example. Many look superb in binoculars or at low power.
- Messier catalogue
The list of 110 deep-sky objects, M1 to M110, that the comet hunter Charles Messier published from 1774 so as not to mistake them for comets (the last entries were added later). It gathers the finest clusters, nebulae and galaxies visible from mid-northern latitudes. It is the ideal observing programme for beginners.
- Milky Way
Our galaxy, a disc about 100,000 light-years across holding more than 100 billion stars; the Sun lies about halfway out. Seen from inside, the disc forms the milky band across dark night skies. It is brightest in summer towards Sagittarius, where the galactic centre lies.
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