Star cluster
Westerlund 1
The most massive young super star cluster in the Milky Way
A "super star cluster" only 3–5 million years old with ~60,000 solar masses: hundreds of giant stars, 24 Wolf-Rayet stars, yellow hypergiants and a magnetar (CXOU J1647). Heavily dimmed by dust in the optical, it shines in the infrared.
| Type | Star cluster |
|---|---|
| Constellation | Ara |
| Distance | 3,900 pc (12,700 light-years) |
| Mass | ~6 × 10⁴ M☉ |
| Age | 3–5 million years |
| Wolf-Rayet stars | 24 |
| Right ascension (J2000) | 16h 47m 04.1s |
| Declination (J2000) | −45° 51′ 04″ |
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 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 226 million years.