Globular cluster
M 22 (NGC 6656)
Globular cluster
A globular cluster of hundreds of thousands of old stars orbiting in the Galaxy’s halo: among the oldest objects of the Milky Way, about 12 billion years old. Its metal abundance is 2.0 % of the Sun’s. Distance, brightness and structure come from the Harris catalogue.
| Type | Globular cluster |
|---|---|
| Constellation | Sagittarius |
| Distance | 3,200 pc (10.4 thousand ly) |
| Metallicity [Fe/H] | -1.70 |
| Half-light radius | 3.1 pc |
| Central concentration (c) | 1.38 |
| Radial velocity | -146.3 km/s |
| Source | Harris 1996 (2010) |
| Right ascension (J2000) | 18h 36m 23.9s |
| Declination (J2000) | −23° 54′ 17″ |
In the sky
Visible from the whole Southern Hemisphere and north to latitude 66° N. South of latitude 66° S it never sets. It stands highest at midnight in June, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 10 thousand years ago. At that time the first farming villages were being founded; there was no writing yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 185 million years.