Star cluster
Mayall II (G1)
The most massive globular cluster in the Local Group
In Andromeda's halo, 130,000 light-years from the centre; a globular cluster of 10 million solar masses, twice the mass of Omega Centauri. Like Omega Centauri it is probably the core of a swallowed dwarf galaxy; it may harbour a ~20,000 M☉ black hole.
| Type | Star cluster |
|---|---|
| Constellation | Andromeda |
| Host galaxy | Andromeda (M31) |
| Distance | 765 kpc (M31 halo) |
| Apparent magnitude | 13,7 |
| Mass | ~10⁷ M☉ |
| Age | ~12 billion years |
| Right ascension (J2000) | 0h 40m 22.6s |
| Declination (J2000) | +39° 34′ 27″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 50° S. North of latitude 50° 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 2.5 million years ago. At that time our ancestors were using stone tools; Homo sapiens did not exist yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 44.3 billion years.