Galaxy · Spiral
Andromeda (M31)
Andromeda (M31) is a galaxy in the direction of the constellation Andromeda, 2.54 million light-years away. The largest galaxy in the Local Group; it will merge with the Milky Way in ~4.5 billion years.
| Type | Spiral |
|---|---|
| Constellation | Andromeda |
| Distance | 2.54 million light-years (780.0 kpc) |
| Diameter | 150,000 light-years · 1.7 × the Milky Way |
| Absolute magnitude | magnitude −21.50 |
| Apparent magnitude | magnitude 2.96 |
| Luminosity | 1.7 × the Milky Way |
| Right ascension (J2000) | 0h 42m 44.4s |
| Declination (J2000) | +41° 16′ 08″ |
| Source | Compiled catalogue (NED, approximate values) |
In the sky
Visible to the naked eye under a dark sky (apparent magnitude 2.96). Visible from the whole Northern Hemisphere and south to latitude 49° S. North of latitude 49° 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 the dinosaurs were gone and mammals were diversifying; there was no human lineage yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 45.1 billion years.