Andromeda
What is Andromeda?
Constellations· Autumn evenings (N) · a chain from the Great Square, home of M31. The chained princess. Two chains of stars stream from a corner of the Great Square, and above Mirach lies the Andromeda Galaxy (M31), the farthest thing visible to the naked eye. Almach is a striking gold-and-blue double star.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Andromeda is in your sky right now: https://nowsky.org/solar/sky?sel=con:Andromeda — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Alpheratz | 2.1 |
| Mirach | 2.1 |
| Almach | 2.3 |
The 3 brightest of the 4 stars used in the figure (3 lines). Lower magnitude means brighter.
Deep-sky objects near this constellation
Constellation basics
| Season | autumn evenings, October–December |
|---|---|
| Brightest star | Alpheratz (2.1) |
| How to find | two lines of stars streaming from the northeast corner of the Great Square |
| Area rank | 19th of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Andromeda?
- autumn evenings, October–December.
- How do I find Andromeda?
- two lines of stars streaming from the northeast corner of the Great Square.
- What is the brightest star in Andromeda?
- Alpheratz, magnitude 2.1.
- Where is Andromeda in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Upsilon Andromedae — the first system with several planets
Upsilon Andromedae, a 4th-magnitude star in Andromeda, was in 1999 the first star other than the Sun confirmed to have several planets. Until then each known exoplanet had been alone at its star; here three were confirmed at once, proving that stars with multiple planets, like the solar system, really exist. At 44 light-years it is visible to the naked eye.
All three planets are heavier than Jupiter, and the orbits of the outer two are tilted nearly 30° to each other. Unlike the solar system, whose planets lie almost in one plane, this was the first case showing that a planetary system can be scattered by its own planets after forming. In Andromeda most people look only for the galaxy M31, but this ordinary star between Alpheratz and Mirach also holds a milestone of planetary research.
The constellation in depth
Andromeda was the daughter of King Cepheus and Queen Cassiopeia of Ethiopia. When her mother's boasting angered Poseidon, he sent the sea monster Cetus, and the king chained his daughter to a seaside rock as a sacrifice. Perseus, arriving on Pegasus, slew the monster and rescued her — and every character in the tale stands together in the autumn sky.
The Andromeda Galaxy, M31, is a spiral 2.5 million light-years away and, with the Milky Way, one of the two great members of the Local Group. To the naked eye it is an elongated smudge above Mirach; in about 4.5 billion years it will collide and merge with our galaxy. Almach, at the chain's end, is a celebrated double of contrasting gold and blue.
On autumn evenings the northeast corner of the Great Square is Alpheratz, and from it Mirach and Almach run northeast in turn. Hop two faint stars upward from Mirach and you reach the pale glow of M31. Set the Sky view to an early November evening with deep-sky objects on to see the galaxy marked, then compare with the real sky.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.