Star cluster
PTB 9
Open star cluster · 1.2 billion 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 | Cepheus |
| Distance | 850 pc (2.8 thousand ly) |
| Age | 1.2 billion years |
| Member stars (MWSC) | 343 |
| Reddening E(B−V) | 0.70 |
| Source | MWSC (Kharchenko et al. 2013) |
| Right ascension (J2000) | 23h 50m 00.6s |
| Declination (J2000) | +68° 01′ 59″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 22° S. North of latitude 22° 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 747 BC. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 49 million years.