Star cluster
Ruprecht 121
Open star cluster · 269 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 | Ara |
| Distance | 1,239 pc (4.0 thousand ly) |
| Age | 269 million years |
| Member stars (MWSC) | 234 |
| Reddening E(B−V) | 1.04 |
| Source | MWSC (Kharchenko et al. 2013) |
| Right ascension (J2000) | 16h 41m 47.4s |
| Declination (J2000) | −46° 08′ 59″ |
In the sky
Visible from the whole Southern Hemisphere and north to latitude 44° N. South of latitude 44° S it never sets. It stands highest at midnight in May, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 4,041 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 72 million years.