Star cluster
Berkeley 91
Open star cluster · 251 million years
An open cluster of stars born together from the same gas cloud in the Milky Way’s disc; the Galaxy’s tidal forces will disperse it within a few hundred million years. Position, distance, age and member count come from the MWSC catalogue; the total brightness is roughly estimated from the member count.
| Type | Star cluster |
|---|---|
| Constellation | Cygnus |
| Distance | 9,471 pc (30.9 thousand ly) |
| Age | 251 million years |
| Member stars (MWSC) | 121 |
| Reddening E(B−V) | 1.30 |
| Source | MWSC (Kharchenko et al. 2013) |
| Right ascension (J2000) | 21h 10m 51.6s |
| Declination (J2000) | +48° 32′ 06″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 41° S. North of latitude 41° N it never sets. It stands highest at midnight in August, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 31 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 548 million years.