M22 · Messier 22
| Chinese name | 人马座球状星团 |
|---|---|
| Type | Globular cluster |
| Constellation | Sgr |
| RA | 18h36m |
| Dec | −23° |
| Apparent magnitude | 5.1ᵐ |
| Hemisphere | Southern |
| Best season | Summer |
| Difficulty | Easy |
| Focal length | 长焦 1000mm+ |
About
M22 lies about 10,000 light-years away in Sagittarius and is one of the nearest and brightest globular clusters, as well as one of the first discovered (1665). Large in apparent size at magnitude 5.1, it is visible to the naked eye as a fuzzy patch under dark skies and its bright, loosely packed stars are easy to resolve. It is one of the few globulars known to contain a planetary nebula and may also host two stellar-mass black holes. It is embedded in the rich Sagittarius Milky Way, surrounded by dense star fields, and lying near the ecliptic it is occasionally passed by planets. It is a popular summer long-focus target, best shot when high above the southern horizon.