Pegasus the Flying Horse, and the best sky story ever

Pegasus the Flying Horse

Pegasus the Flying Horse rises in the east on autumn evenings in the Northern Hemisphere (spring evenings in the Southern Hemisphere). It dominates the sky with its giant square asterism, fittingly called the Great Square. In mythology, Pegasus figured into the greatest – surely the most elaborate – of all sky myths. This one is from ancient Greece some 3,000 years ago. According to the myth, Pegasus was the flying horse ridden by Perseus the Hero, as he swooped in to save Princess Andromeda from a sea monster. There’s more to the story, which you’ll find in the video at the top of this page.

Today, we see Pegasus as the 7th-largest of the 88 official constellations. And Pegasus is easy to find. On fall evenings in the Northern Hemisphere, this constellation climbs above the eastern horizon, reaching a spot nearly overhead by late fall.

Its asterism – the Great Square of Pegasus – is huge. The square alone is 20 degrees wide from top to bottom. That’s the span of two fist-widths held at arm’s length.

On autumn evenings in the Northern Hemisphere – spring evenings in the Southern Hemisphere – Pegasus the Flying Horse is ascending in the east in the evening hours. You’ll most easily notice the giant, square-shaped asterism within Pegasus, called the Great Square.

The 2025 EarthSky Lunar Calendar presale is here! The first 100 purchases are signed by the legendary Deborah Byrd as a thank you. Get yours today!

Stars of Pegasus

As it rises in the evening, the star in the Great Square closest to the horizon is Algenib, with a magnitude of 2.8. It lies 390 light-years away. The star on the opposite corner of the square from Algenib is Scheat, a magnitude 2.4 star lying 199 light-years away. The star to the south in the square is Markab, a magnitude 2.5 star at a distance of 140 light-years. And the final star in the square is Alpheratz. Technically, Alpheratz lies just across the border of Pegasus and is actually a member of the constellation Andromeda. Alpheratz is the brightest of the four stars at magnitude 2.1 and lies 97 light-years away.

The Great Square marks the body of the flying horse. Trails leading off the west side of the square mark the front legs and head of Pegasus. Extending out from Markab, two stars at magnitude 3.4 and 3.5, Homam and Biham, lead the way to the head star, magnitude 2.4 star Enif. This star is helpful in finding the globular cluster M15.

Find the forelegs of Pegasus off of Scheat. Five degrees west of Scheat is 3rd magnitude star Matar. As the brightest leg star in Pegasus, it’s helpful in finding a couple of notable galaxies.

Pegasus the Flying Horse is a giant constellation that rises in the east on October evenings. Image via Stellarium. Used with permission.

The asterism of the Great Square

The Great Square of Pegasus can look like a huge diamond. Think of it as a giant baseball diamond rising during playoffs month in the east after dark. Asterisms, such as the Great Square, are groups of stars that aren’t labeled as constellations but are easy to recognize.

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, India, captured this photo of Pegasus. He wrote: “Pegasus is named after the winged horse in Greek mythology. Curiously, the constellation Pegasus only represents the top half of the horse. In some depictions, the horse is shown rising out of the water. Viewed best in autumn, turn your eyes to the east as the night falls, and see the winged horse rising high up in the sky.” Thank you, Prateek!

Using Pegasus to find the Andromeda Galaxy

Pegasus is close to the constellation Andromeda, so it’s useful for star-hopping to the Andromeda galaxy. You’ll need a dark-sky site to track down Andromeda without optical aid. It’s much easier to spot with binoculars or a telescope. Follow this link for more information on how to use Pegasus to find Andromeda.

Find the Andromeda Galaxy (M31) by star-hopping from the Great Square of Pegasus. Chart via EarthSky.

View at EarthSky Community Photos. | Jan Curtis in Cheyenne, Wyoming, caught Messier 31, the Andromeda Galaxy, on September 25, 2024. Jan wrote: “M31 is well-placed this time of year for all-night viewing.” Thank you, Jan!

Stephan’s Quintet

Pegasus is home to many galaxy clusters. The most famous is probably Stephan’s Quintet, a favorite target among astrophotographers. This tight gathering of five galaxies has a faint magnitude of 13.6. The largest and brightest, NGC 7320, has a small redshift compared to the other four, revealing that it is probably not a physical member of the group and just a line-of-sight coincidence.

Fun fact: In the 1946 movie It’s a Wonderful Life, angels in heaven discussing George Bailey are depicted as the galaxies in Stephan’s Quintet.

View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured two galaxy groups, namely Stephan’s Quintet and the Deer Lick Group, both in the constellation Pegasus, on October 27, 2024. Andy wrote: “Over the years I have run into pictures and discussions of these two objects. Both are rather small and close together. Their data and histories are fun too. Both of these would be seen better with a 2,000 mm telescope and my 600 mm telescope with a small format camera takes a pretty good pic. What fun exploring the universe is. I seem to be on a roll lately, lots of clear skies and a motivated photographer.” Thank you, Andy!

This image of Stephan’s Quintet is from 2009, courtesy of the Hubble Space Telescope. Image via Wikimedia Commons (public domain)/ NASA/ ESA/ and the Hubble SM4 ERO Team.

Other galaxies in Pegasus the Flying Horse

Three other notable galaxy clusters lie in Pegasus. The brightest is magnitude 9.5 and is just half a degree from Stephan’s Quintet. The cluster has the curious name Deer Lick Group. Follow Scheat to Matar and then about 4.5 degrees farther and slightly north of the direction you were heading. This will bring you to the Deer Lick Group, NGC 7331. Here you’ll find one large spiral galaxy and a spattering of smaller ones.

The Deer Lick Group contains one large spiral galaxy and other smaller galaxies. It lies in the constellation Pegasus. Image via W4sm astro/ Wikimedia Commons (CC BY-SA 4.0).

The Pegasus I Cluster lies on the southern edge of the constellation not far from the circlet of Pisces. At a distance of 8 degrees from Markab on the sky’s dome, the Pegasus I Cluster is a grouping with a magnitude of 11.1. The galaxy cluster requires a large telescope to see or a long-exposure photograph, but it reveals a beautiful and striking number of galaxies.

The Pegasus II Cluster lies back within the square of Pegasus. Halfway between Alpheratz and Scheat, it lies just inside the border of a line that would be drawn connecting these two stars. A bit dimmer at magnitude 12.6, the Pegasus II Cluster (NGC 7720) is a powerful radio source, the target of much scientific study.

Globular Cluster M15 in Pegasus the Flying Horse

One other deep-sky object of note in Pegasus is the globular cluster M15. You can find M15 easily using the head and neck stars of Pegasus. Start with the star Markab and go to the two dimmer stars that mark the neck. From the last star of the neck (Biham) to the brighter head star Enif, continue a line straight out for a little more than 4 degrees. Here you will find the magnitude 6.4 globular cluster M15. It lies about 33,600 light-years away and will show up nicely in a pair of binoculars.

You can find the globular cluster M15 in the constellation Pegasus. It shines at magnitude 6.4. Image via Mount Lemmon SkyCenter Schulman Telescope/ Adam Block/ Wikimedia Commons (CC BY-SA 4.0).

First exoplanet around a sun-like star

Astronomers discovered the first exoplanet orbiting a sun-like star in the constellation Pegasus. They named the planet 51 Pegasi b after the star it orbits. Didier Queloz and Michel Mayor discovered the planet in 1995 and received the Nobel Prize in Physics for their discovery in 2019.

Artist’s concept of the hot Jupiter exoplanet 51 Pegasi b. The first planet discovered around a sun-like star, 51 Pegasi b lies about 50 light-years from Earth in the constellation Pegasus the Flying Horse. Image via ESO/ M. Kornmesser/ Nick Risinger/ Wikimedia Commons (CC BY 4.0).

Bottom line: Pegasus the Flying Horse is a giant constellation that dominates autumn skies in the Northern Hemisphere (spring skies in the Southern Hemisphere). The constellation contains a famous asterism called the Great Square.

The post Pegasus the Flying Horse, and the best sky story ever first appeared on EarthSky.

from EarthSky https://ift.tt/rFLQO0l

Pegasus the Flying Horse

Pegasus the Flying Horse rises in the east on autumn evenings in the Northern Hemisphere (spring evenings in the Southern Hemisphere). It dominates the sky with its giant square asterism, fittingly called the Great Square. In mythology, Pegasus figured into the greatest – surely the most elaborate – of all sky myths. This one is from ancient Greece some 3,000 years ago. According to the myth, Pegasus was the flying horse ridden by Perseus the Hero, as he swooped in to save Princess Andromeda from a sea monster. There’s more to the story, which you’ll find in the video at the top of this page.

Today, we see Pegasus as the 7th-largest of the 88 official constellations. And Pegasus is easy to find. On fall evenings in the Northern Hemisphere, this constellation climbs above the eastern horizon, reaching a spot nearly overhead by late fall.

Its asterism – the Great Square of Pegasus – is huge. The square alone is 20 degrees wide from top to bottom. That’s the span of two fist-widths held at arm’s length.

On autumn evenings in the Northern Hemisphere – spring evenings in the Southern Hemisphere – Pegasus the Flying Horse is ascending in the east in the evening hours. You’ll most easily notice the giant, square-shaped asterism within Pegasus, called the Great Square.

The 2025 EarthSky Lunar Calendar presale is here! The first 100 purchases are signed by the legendary Deborah Byrd as a thank you. Get yours today!

Stars of Pegasus

As it rises in the evening, the star in the Great Square closest to the horizon is Algenib, with a magnitude of 2.8. It lies 390 light-years away. The star on the opposite corner of the square from Algenib is Scheat, a magnitude 2.4 star lying 199 light-years away. The star to the south in the square is Markab, a magnitude 2.5 star at a distance of 140 light-years. And the final star in the square is Alpheratz. Technically, Alpheratz lies just across the border of Pegasus and is actually a member of the constellation Andromeda. Alpheratz is the brightest of the four stars at magnitude 2.1 and lies 97 light-years away.

The Great Square marks the body of the flying horse. Trails leading off the west side of the square mark the front legs and head of Pegasus. Extending out from Markab, two stars at magnitude 3.4 and 3.5, Homam and Biham, lead the way to the head star, magnitude 2.4 star Enif. This star is helpful in finding the globular cluster M15.

Find the forelegs of Pegasus off of Scheat. Five degrees west of Scheat is 3rd magnitude star Matar. As the brightest leg star in Pegasus, it’s helpful in finding a couple of notable galaxies.

Pegasus the Flying Horse is a giant constellation that rises in the east on October evenings. Image via Stellarium. Used with permission.

The asterism of the Great Square

The Great Square of Pegasus can look like a huge diamond. Think of it as a giant baseball diamond rising during playoffs month in the east after dark. Asterisms, such as the Great Square, are groups of stars that aren’t labeled as constellations but are easy to recognize.

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, India, captured this photo of Pegasus. He wrote: “Pegasus is named after the winged horse in Greek mythology. Curiously, the constellation Pegasus only represents the top half of the horse. In some depictions, the horse is shown rising out of the water. Viewed best in autumn, turn your eyes to the east as the night falls, and see the winged horse rising high up in the sky.” Thank you, Prateek!

Using Pegasus to find the Andromeda Galaxy

Pegasus is close to the constellation Andromeda, so it’s useful for star-hopping to the Andromeda galaxy. You’ll need a dark-sky site to track down Andromeda without optical aid. It’s much easier to spot with binoculars or a telescope. Follow this link for more information on how to use Pegasus to find Andromeda.

Find the Andromeda Galaxy (M31) by star-hopping from the Great Square of Pegasus. Chart via EarthSky.

View at EarthSky Community Photos. | Jan Curtis in Cheyenne, Wyoming, caught Messier 31, the Andromeda Galaxy, on September 25, 2024. Jan wrote: “M31 is well-placed this time of year for all-night viewing.” Thank you, Jan!

Stephan’s Quintet

Pegasus is home to many galaxy clusters. The most famous is probably Stephan’s Quintet, a favorite target among astrophotographers. This tight gathering of five galaxies has a faint magnitude of 13.6. The largest and brightest, NGC 7320, has a small redshift compared to the other four, revealing that it is probably not a physical member of the group and just a line-of-sight coincidence.

Fun fact: In the 1946 movie It’s a Wonderful Life, angels in heaven discussing George Bailey are depicted as the galaxies in Stephan’s Quintet.

View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured two galaxy groups, namely Stephan’s Quintet and the Deer Lick Group, both in the constellation Pegasus, on October 27, 2024. Andy wrote: “Over the years I have run into pictures and discussions of these two objects. Both are rather small and close together. Their data and histories are fun too. Both of these would be seen better with a 2,000 mm telescope and my 600 mm telescope with a small format camera takes a pretty good pic. What fun exploring the universe is. I seem to be on a roll lately, lots of clear skies and a motivated photographer.” Thank you, Andy!

This image of Stephan’s Quintet is from 2009, courtesy of the Hubble Space Telescope. Image via Wikimedia Commons (public domain)/ NASA/ ESA/ and the Hubble SM4 ERO Team.

Other galaxies in Pegasus the Flying Horse

Three other notable galaxy clusters lie in Pegasus. The brightest is magnitude 9.5 and is just half a degree from Stephan’s Quintet. The cluster has the curious name Deer Lick Group. Follow Scheat to Matar and then about 4.5 degrees farther and slightly north of the direction you were heading. This will bring you to the Deer Lick Group, NGC 7331. Here you’ll find one large spiral galaxy and a spattering of smaller ones.

The Deer Lick Group contains one large spiral galaxy and other smaller galaxies. It lies in the constellation Pegasus. Image via W4sm astro/ Wikimedia Commons (CC BY-SA 4.0).

The Pegasus I Cluster lies on the southern edge of the constellation not far from the circlet of Pisces. At a distance of 8 degrees from Markab on the sky’s dome, the Pegasus I Cluster is a grouping with a magnitude of 11.1. The galaxy cluster requires a large telescope to see or a long-exposure photograph, but it reveals a beautiful and striking number of galaxies.

The Pegasus II Cluster lies back within the square of Pegasus. Halfway between Alpheratz and Scheat, it lies just inside the border of a line that would be drawn connecting these two stars. A bit dimmer at magnitude 12.6, the Pegasus II Cluster (NGC 7720) is a powerful radio source, the target of much scientific study.

Globular Cluster M15 in Pegasus the Flying Horse

One other deep-sky object of note in Pegasus is the globular cluster M15. You can find M15 easily using the head and neck stars of Pegasus. Start with the star Markab and go to the two dimmer stars that mark the neck. From the last star of the neck (Biham) to the brighter head star Enif, continue a line straight out for a little more than 4 degrees. Here you will find the magnitude 6.4 globular cluster M15. It lies about 33,600 light-years away and will show up nicely in a pair of binoculars.

You can find the globular cluster M15 in the constellation Pegasus. It shines at magnitude 6.4. Image via Mount Lemmon SkyCenter Schulman Telescope/ Adam Block/ Wikimedia Commons (CC BY-SA 4.0).

First exoplanet around a sun-like star

Astronomers discovered the first exoplanet orbiting a sun-like star in the constellation Pegasus. They named the planet 51 Pegasi b after the star it orbits. Didier Queloz and Michel Mayor discovered the planet in 1995 and received the Nobel Prize in Physics for their discovery in 2019.

Artist’s concept of the hot Jupiter exoplanet 51 Pegasi b. The first planet discovered around a sun-like star, 51 Pegasi b lies about 50 light-years from Earth in the constellation Pegasus the Flying Horse. Image via ESO/ M. Kornmesser/ Nick Risinger/ Wikimedia Commons (CC BY 4.0).

Bottom line: Pegasus the Flying Horse is a giant constellation that dominates autumn skies in the Northern Hemisphere (spring skies in the Southern Hemisphere). The constellation contains a famous asterism called the Great Square.

The post Pegasus the Flying Horse, and the best sky story ever first appeared on EarthSky.

from EarthSky https://ift.tt/rFLQO0l