Star cluster
Alessi 20
Open star cluster · 38 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 | 470 pc (1.5 thousand ly) |
| Age | 38 million years |
| Member stars (MWSC) | 101 |
| Reddening E(B−V) | 0.38 |
| Source | MWSC (Kharchenko et al. 2013) |
| Right ascension (J2000) | 0h 10m 40.1s |
| Declination (J2000) | +58° 44′ 53″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 31° S. North of latitude 31° N it never sets. It stands highest at midnight in September, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out around the year 493. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 27 million years.