Globular cluster
M 71 (NGC 6838)
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 17 % of the Sun’s. Distance, brightness and structure come from the Harris catalogue.
| Type | Globular cluster |
|---|---|
| Constellation | Sagitta |
| Distance | 4,000 pc (13.0 thousand ly) |
| Metallicity [Fe/H] | -0.78 |
| Half-light radius | 1.9 pc |
| Central concentration (c) | 1.15 |
| Radial velocity | -22.8 km/s |
| Source | Harris 1996 (2010) |
| Right ascension (J2000) | 19h 53m 46.5s |
| Declination (J2000) | +18° 46′ 45″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 71° S. North of latitude 71° N it never sets. It stands highest at midnight in July, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 13 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 231 million years.