Star cluster
SAI 21
Open star cluster · 891 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 | Cassiopeia |
| Distance | 1,900 pc (6.2 thousand ly) |
| Age | 891 million years |
| Member stars (MWSC) | 44 |
| Reddening E(B−V) | 0.65 |
| Source | MWSC (Kharchenko et al. 2013) |
| Right ascension (J2000) | 2h 34m 49.8s |
| Declination (J2000) | +62° 35′ 17″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 27° S. North of latitude 27° N it never sets. It stands highest at midnight in October, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 6,197 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 110 million years.