Autumn Sky Guide: Pegasus and the Andromeda Galaxy

## Autumn Sky: The Royal Court

The autumn sky (September-November, Northern Hemisphere) features the mythological royal family — Cassiopeia, Cepheus, Andromeda, Perseus, and Pegasus — along with the most distant object visible to the naked eye.

### The Great Square of Pegasus

The Great Square is the anchor of the autumn sky, a large roughly square asterism spanning about 15 degrees on each side:

| Star | Name | Constellation | Magnitude |
|------|------|---------------|-----------|
| Alpha And | Alpheratz | Andromeda | +2.06 |
| Beta Peg | Scheat | Pegasus | +2.42 |
| Alpha Peg | Markab | Pegasus | +2.49 |
| Gamma Peg | Algenib | Pegasus | +2.84 |

Note: Alpheratz is technically in Andromeda, shared with the Square's corner. Under moderately dark skies, the interior of the Square appears remarkably empty — a useful gauge of sky transparency. If you can see 4+ stars inside, conditions are good.

### Finding the Andromeda Galaxy

From the Great Square, follow the chains of Andromeda northeast:

1. Start at Alpheratz (NE corner of the Square)
2. Follow the line of stars northeast through Mirach to Mu Andromedae
3. Turn 90 degrees north from Mirach — M31 lies about 4 degrees away
4. Under dark skies, M31 appears as a faint elongated glow — at magnitude +3.44, it is the most distant object visible without a telescope at 2.537 million light-years

### Autumn Highlights

| Object | Type | Magnitude | Distance |
|--------|------|-----------|----------|
| M31 (Andromeda Galaxy) | Spiral galaxy | +3.44 | 2.537 Mly |
| Double Cluster (NGC 869/884) | Open clusters | +4.3 | 7,500 ly |
| M33 (Triangulum Galaxy) | Spiral galaxy | +5.72 | 2.73 Mly |
| NGC 7789 (Caroline's Rose) | Open cluster | +6.7 | 7,600 ly |
| Algol (Beta Per) | Eclipsing binary | +2.1-3.4 | 93 ly |

### Fomalhaut: The Lonely Star

**Fomalhaut** (Alpha Piscis Austrini, magnitude +1.16, 25 ly) is the only first-magnitude star in the autumn sky, earning it the nickname "The Autumn Star" or "The Loneliest Star." It sits low in the south, isolated from other bright stars. In 2008, it became one of the first stars with a directly imaged exoplanet candidate (Fomalhaut b), though the object may be a dust cloud.

### Meteor Showers

The **Orionids** (October 21-22, ~20/hour) are debris from Halley's Comet, while the **Leonids** (November 17-18) occasionally produce spectacular storms — in 1966, observers counted over 100,000 meteors per hour.