Pegasus Constellation Guide – Midnight’s Winged Horse

In this article, we’ll be sharing with you everything you need to know about the constellation of Pegasus, including how to find it, deep space objects contained within it, and how to use it to find other night sky objects more easily.

Table Of Contents

The Constellation of Pegasus

This constellation was cataloged by Ptolemy more than 2000 years ago. In Greek mythology, Pegasus was the winged horse that flew out of Medusa’s neck when Perseus beheaded her. In other versions of the myth, Pegasus was the offspring of Medusa and Poseidon, God of The Sea.

A third famous myth about Pegasus is that of Bellerophon. Bellerophon was the hero who was sent to kill the Chimaera. Athena helped Bellerophon tame Pegasus and the hero rode the flying horse while shooting arrows at the Chimaera. The Chimaera was killed and Bellerophon went on to complete several other heroic deeds for his king.

Bellerophon decided to join the Gods in Olympus and persuaded Pegasus to take him there. Zeus sent a gadfly to sting Pegasus causing Bellerophon to fall back to Earth. Pegasus reached Olympus alone and Zeus used the winged horse to carry his thunder and lightning and later placed him among the stars.

To help you spot Pegasus, here’s how SkySafari 6 shows the winged horse.

The flying horse sitting behind the constellation of Pegasus
Pegasus constellation shown as a flying horse. Click for full-screen

Pegasus has an area of 1,121 square degrees making it the 7th largest of the 88 recognized constellations. The constellation represents the front half of the winged horse and is known for the ‘Great Square of Pegasus’ asterism. Its corners are marked by the four bright stars Alpheratz, Scheat, Markab, and Algenib.

The Great Square of Pegasus asterism
The Great Square of Pegasus asterism. Click for full-screen

In the next section discover how to find Pegasus.

How To Find Pegasus In The Night Sky

Pegasus is part of the Perseus family of constellations and is visible to observers at latitudes between +90° and -60°. Northern Hemisphere observers can see Pegasus in the evening from July to January, while Southern Hemisphere observers can see it from December to May.

Finding Pegasus in the night sky
Pegasus high in the west at 8 pm in early January. Click for full-screen.

The constellation of Pegasus is larger than just its Great Square, extending out west several degrees. See the whole area inside the International Astronomical Union’s boundaries in the image below. You can see that Pegasus is bordered by the constellations (from the top, clockwise) Lacerta, Cygnus, Vulpecula, Delphinus, Equuleus, Aquarius, Pisces, and Andromeda.

Pegasus and its surrounding constellations. Click for full-screen.

To find Pegasus, do a naked-eye search for the Great Square of Pegasus. The four stars in this asterism are Scheat, Alpheratz, Markab, and Algenib are of nearly equal brightness.

Alternatively, do a naked-eye search for the Little Dipper and Polaris. Draw an imaginary line from Polaris to Caph in Cassiopeia (~30°) then extend this line ~30° to the Great Square of Pegasus.

Finding Pegasus from Polaris
Finding Pegasus from Polaris via Cassiopeia. Click for full-screen.

To find Pegasus’s exact position for your location on any night, use software such as Stellarium (free) or SkySafari 6, which has produced the star maps on this page.

The Brightest Stars of Pegasus

Pegasus contains several notable stars brighter than magnitude 5.0. See them on the image below, which can be clicked for a full-screen version. There’s more detail about each star underneath the image.

Named bright stars in the constellation of Pegasus
Bright stars of Pegasus. Click for full-screen.

Alpha Pegasi (Markab) – This magnitude 2.49 blue-white main-sequence star, is the third-brightest star in Pegasus and marks the southwest corner of the Great Square. Markab is 140 light-years away, and its name comes from the Arabic word for ‘saddle’.

Beta Pegasi (Scheat) – This variable double star is the second-brightest star in the constellation of Pegasus and marks the northwest corner of the Great Square.

The 2.47 magnitude orange-red giant and its magnitude 12.00 secondary component are 129.6 arcseconds apart. The primary is a pulsating variable whose magnitude ranges from 2.31 to 2.74. Scheat is 200 light-years away and means ‘the shin’ or ‘the foreleg’ in Arabic.

Gamma Pegasi (Algenib) – This double star is the fourth-brightest star in Pegasus and marks the southeast corner of the Great Square. The double is composed of a magnitude 2.82 blue subgiant primary and a magnitude 12.66 secondary which are 164 arcseconds apart.

The primary is a pulsating variable whose magnitude fluctuates between 2.78 to 2.89 over 0.15 days (about 22 minutes). Algenib is 335 light-years away and its name means ‘the side’ in Arabic. This traditional name originally belonged to Alpha Perseus.

Delta Pegasi (Alpheratz, Alpha Andromedae) – This would be the brightest star in Pegasus and it is also a double. Alpheratz marks the northeast corner of the Great Square of Pegasus.

The name Delta Pegasi is no longer in use because the star is formally part of the constellation of Andromeda, it is included here because it is one corner of the Great Square. The star is properly cataloged as Alpha Andromedae. See the SkySafari 6 image below showing the IAU boundary between Pegasus and Andromeda weaving around Alpheratz.

The star Alpheratz inside the constellation of Andromeda's boundary, just outside of Pegasus
Showing Alpheratz inside Andromeda’s boundary. Click for full-screen.

The 2.05 magnitude blue-white subgiant primary and 11.11 magnitude secondary components are 91.2 arcseconds apart. The Alpheratz system is 97 light-years away and its name commonly means ‘the horse’s shoulder’.

Epsilon Pegasi (Enif) – This variable double star is the brightest in Pegasus at magnitude 2.39 and is 670 light-years away. It’s a double star, the primary is an orange-red giant and the secondary is a magnitude 12.80 star 83 arcseconds away. The primary is a long-period pulsating variable whose magnitude ranges from 0.70 to 3.50.

Enif means ‘the nose’ in Arabic and this star marks Pegasus’s muzzle.

Zeta Pegasi (Homam) – This double star is the sixth-brightest star in Pegasus and is 209 light-years away. The 3.42 magnitude blue-white main-sequence primary and 11.60 magnitude secondary components are 57.9 arcseconds apart.

Homam is derived from the Arabic phrase ‘lucky stars of the hero’, a name that originally belonged to both Zeta Pegasi and Xi Pegasi.

Eta Pegasi (Matar) – This double star is the fifth-brightest star in Pegasus and is 215 light-years away. The 2.94 magnitude yellow-orange giant primary and 9.87 magnitude secondary components are 94.4 arcseconds apart. Matar is Arabic for ‘lucky star of rain’.

Theta Pegasi (Baham) – This magnitude 3.52 white main-sequence star is 92 light-years away from us.

Iota Pegasi – This double star system is 38 light-years away. The 3.76 magnitude yellow-white main sequence primary and its magnitude 11.26 secondary component are too close to each other to be separated in a telescope for astronomy.

Kappa Pegasi – This double star is 112 light-years away. The magnitude 4.15 magnitude yellow-white subgiant primary is just 0.3 arcseconds from the magnitude 5.04 secondary component.

Lambda Pegasi – This 3.96 magnitude orange giant is 365 light-years away. It has a mass of 1.1 Solar masses, a diameter of 28.2 Solar diameters, and is 17% cooler than the Sun.

Mu Pegasi – This 3.50 magnitude yellow-orange star is 106 light-years away. Its luminosity is 36 times that of the Sun.

Nu Pegasi – This 4.84 magnitude orange giant is 272 light-years away.

Xi Pegasi – This double star is 53 light-years away. The 4.21 magnitude yellow-white giant primary star and its magnitude 12.40 secondary are 11.1 arcseconds apart.

Omicron Pegasi – This 4.80 magnitude blue-white subgiant star is 299 light-years away. Its mass is 2.7 Solar masses, its diameter is 3.8 Solar diameters, and it’s 1.6 times hotter than the Sun.

Pi2 Pegasi – This 4.28 magnitude yellow-white giant is 263 light-years away. It has a mass of 1.3 Solar masses, a diameter of 7.0 Solar diameters and, is 1.3 times hotter than the Sun.

Rho Pegasi – This 4.90 magnitude white main-sequence star is 312 light-years away. It has a mass of 2.7 Solar masses, a diameter of 3.8 Solar diameters, and is 1.6 times hotter than the Sun.

Tau Pegasi (Kerb) – This 4.59 magnitude white main-sequence variable star is 162 light-years away.

Upsilon Pegasi – This magnitude 4.42 yellow giant is 170 light-years away from Earth. It has a mass of 1.1 Solar masses, a diameter of 5.4 Solar diameters, and is 1.1 times hotter than the Sun.

Chi Pegasi – This 4.80 magnitude orange-red star is 368 light-years away.

Psi Pegasi – This double star is 476 light-years away. The magnitude 4.65 orange-red giant primary and its secondary component are 0.1 arcseconds apart and can’t be resolved in a backyard telescope.

Star Hopping From Pegasus

Pegasus is the starting point for several well-known star hops due to the easily recognized Great Square. Use our guide to measuring distances in the night sky to help with these hopping routes.

Gamma Andromedae (Almach) – Almach is one of the most famous double stars in the night sky. To get there from Pegasus, identify Alpheratz in the Great Square of Pegasus, then hop ~6° east from there to Delta Andromedae (on the southern ‘leg’ of Andromeda). Continue northeastwards along the leg ~8° to Mirach, and finally ~12° northeast to Almach.

Triangulum Constellation – In the Great Square of Pegasus, draw an imaginary line from Apheratz to Scheat (~15°) then, double this line to the constellation Triangulum.

Cetus Constellation – Identify Algenib in the Great Square of Pegasus. Draw an imaginary line ~40° east to the circle of stars that represent the head of the sea monster.

M15 (Globular Cluster) – To find this cluster inside the boundary of Pegasus, identify Markab in the Great Square of Pegasus. From there, hop ~7° southwest to Homam, and then on another ~9° in the same direction to Baham. At Baham, swing northwest and travel ~7° to Enif. A final hop along the same direction of ~4° brings you to M15.

M31 (Andromeda Galaxy) – Identify Alpheratz in the Great Square of Pegasus. Hop ~6° east to Delta Andromedae, ~8° northeast to Mirach, ~4° northwest to Mu Andromedae, and then ~4° northwest to M31.

Read our detailed guide to finding Andromeda Galaxy (M31)

M74 (Spiral Galaxy)  – Identify Algenib in the Great Square of Pegasus. Draw an imaginary line ~20° east to Eta Piscium (Kullat Nunu) then ~1° east-northeast to M74.

M76 (Little Dumbbell Nebula)– Identify Alpheratz in the Great Square of Pegasus. Hop ~6° east to Delta Andromedae, then ~8° northeast to Mirach, and continue the same line for ~12° to Almach. From Almach, travel ~9° northwest to Phi Persei, and finally ~1° north to M76.

NGC 404 (Mirach’s Ghost) – Identify Alpheratz in the Great Square of Pegasus. Hop ~6° east to Delta Andromedae and then ~8° northeast to Mirach. NGC 404 is in the same 1° field of view as Mirach, just seven arcminutes northwest of the star.

NGC 7331 (Spiral Galaxy) – To find this magnitude 9 galaxy in Perseus, identify the star Scheat in the Great Square. Hop ~5° northwest to Matar, then 4.5° north to the galaxy itself.

Objects To See Within Pegasus

Pegasus contains one Messier object and few other deep sky objects for small telescopes to hunt out and enjoy.

M15 (NGC 7078) – This globular cluster has a magnitude of 6.19 and an apparent size of 18.0 arcminutes. It’s 33,600 light-years away and found at right ascension 21h 29m 58s and declination +12° 10’ 01” (J2000.0).

NGC 7217  – This spiral galaxy has a magnitude of 10.04 and an apparent size of 4.5 x 3.8 arcminutes. It’s 50 million light-years away and is at right ascension 22h 07m 52s and declination +31° 21’ 33”.

NGC 7331  – This spiral galaxy has a magnitude of 9.25 and an apparent size of 9.3 x 3.8 arcminutes. It’s 46 million light-years away and is at right ascension 22h 37m 04s and declination +34° 24’ 56”.

NGC 7479 – This spiral galaxy has a magnitude of 10.86 and an apparent size of 3.6 x 2.7 arcminutes. It’s 98 million light-years away and is at right ascension 23h 04m 56s and declination +12° 19’ 22”.

NGC 7814 – This spiral galaxy has a magnitude of 10.51 and an apparent size of 4.4 x 1.9 arcminutes. It’s 47 million light-years away and is at right ascension 00h 03m 15s and declination +16° 08’ 44”.

Summary

Pegasus is a large constellation with many notable stars and some deep sky objects. The Great Square of Pegasus is the famous starting point for several star hops.

Enjoy this constellation’s wonders in later summer and early autumn.


Written by Tanya C. Forde