Globular cluster
AL 3 (BH 261)
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 5.0 % of the Sun’s. Distance, brightness and structure come from the Harris catalogue.
| Type | Globular cluster |
|---|---|
| Constellation | Sagittarius |
| Distance | 6,500 pc (21.2 thousand ly) |
| Metallicity [Fe/H] | -1.30 |
| Half-light radius | 1.0 pc |
| Central concentration (c) | 1.00 |
| Source | Harris 1996 (2010) |
| Right ascension (J2000) | 18h 14m 06.6s |
| Declination (J2000) | −28° 38′ 06″ |
In the sky
Visible from the whole Southern Hemisphere and north to latitude 61° N. South of latitude 61° 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 21 thousand years ago. At that time Homo sapiens was spreading out of Africa; there was no farming yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 376 million years.