Globular cluster
NGC 6397
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 1.0 % of the Sun’s. Distance, brightness and structure come from the Harris catalogue.
| Type | Globular cluster |
|---|---|
| Constellation | Ara |
| Distance | 2,300 pc (7.5 thousand ly) |
| Metallicity [Fe/H] | -2.02 |
| Half-light radius | 1.9 pc |
| Central concentration (c) | 2.50 · core-collapsed |
| Radial velocity | 18.8 km/s |
| Source | Harris 1996 (2010) |
| Right ascension (J2000) | 17h 40m 42.1s |
| Declination (J2000) | −53° 40′ 27″ |
In the sky
Visible from the whole Southern Hemisphere and north to latitude 36° N. South of latitude 36° 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 7,502 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 133 million years.