Globular cluster
HP 3 (Terzan 2)
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 20 % of the Sun’s. Distance, brightness and structure come from the Harris catalogue.
| Type | Globular cluster |
|---|---|
| Constellation | Scorpius |
| Distance | 7,500 pc (24.5 thousand ly) |
| Metallicity [Fe/H] | -0.69 |
| Half-light radius | 3.3 pc |
| Central concentration (c) | 2.50 · core-collapsed |
| Radial velocity | 109.0 km/s |
| Source | Harris 1996 (2010) |
| Right ascension (J2000) | 17h 27m 33.1s |
| Declination (J2000) | −30° 48′ 08″ |
In the sky
Visible from the whole Southern Hemisphere and north to latitude 59° N. South of latitude 59° 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 24 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 434 million years.