PEGASUS & ANDROMEDA - CONSTELLATION OF THE MONTH
Pegasus is a large constellation in the northern sky that is easily distinguished by 4 bright stars that make a giant square, known by the asterism The Great Square of Pegasus. Pegasus represents a mythological white winged horse sired by Poseidon and the Gorgon, Medusa.
Pegasus was involved in many great Greek stories, including the slaying of the fearsome, fire-breathing monster, Chimera by the hero Bellerophon. In some accounts, it also played a part in the famous myth of Princess Andromeda’s rescue at the hands of a great sea monster, Cetus.
Andromeda’s parents, King Cepheus and Queen Cassiopeia were so proud of their daughter that Cassiopeia boasted she was the most beautiful woman alive, mortal or immortal. This angered Poseidon, who sent Cetus, a giant sea monster to attack their coastal city. The rulers consulted the oracle who told them they must sacrifice Andromeda to the monster or risk destruction.
Andromeda was chained to a rock and left to the mercy of the beast. Before Cetus could take her, the great hero Perseus, fresh from killing Medusa, arrived on the back of Pegasus and hearing her cries of distress, swooped down to assist. Perseus had with him the severed head of Medusa, whose gaze would turn anyone to stone that looked at it, and thrust it towards Cetus. Cetus was instantly turned to stone and Perseus whisked Andromeda away to be his wife.
All 6 characters in this story are immortalised in the heavens, with the constellations of Pegasus, Andromeda, Perseus and Cetus all visible from South Africa, whilst Cepheus and Cassiopeia are only visible from more northern latitudes.
Enif, The Muzzle
Enif comes from the Arabic word for ‘nose’ and marks the muzzle of the great winged horse. Situated around 700 light years away, Enif still burns brightly in the night sky thanks to its size. Enif is an orange/red supergiant with an estimated diameter of nearly 200x that of our Sun and burns around 5000 times brighter.
Alpheratz, The Navel
The blue/white subgiant star, Alpheratz used to be shared between the constellations of Pegasus and Andromeda, but in 1930 was officially designated to Andromeda and thus marks its brightest star. Alpheratz still makes up 1 of the of 4 corners of the famous asterism, the Great Square of Pegasus, along with Markab (saddle), Sheat (shin) and Algenib (flank). Its obviousness in the sky has also made it an important navigation star throughout history.
DEEP SKY OBJECTS
Messier 31, The Andromeda Galaxy
The Andromeda Galaxy is the closest major galaxy to our own Milky Way and can be spotted with the naked eye under dark skies. It is the furthest object visible from Earth without the use of optical equipment and resides around 2.5 million light years away. It has a spiral structure similar to our own galaxy but is much larger, estimated to contain close to a trillion stars! Andromeda and the Milky Way are being pulled together at around 500km/s thanks to their mutual gravities, and it is predicted that the 2 galaxies will merge in around 4 billion years’ time, combining to form a giant elliptical galaxy.
Messier 15, The Pegasus Cluster
The Pegasus Cluster is a huge group of ancient stars arranged in spheroidal shape known as a globular cluster. It is one of 200 such objects in the sky and is considered one of the largest and brightest.
Situated a massive 33,000 light years away, Messier 15 contains over 100,000 stars all orbiting a common centre, most likely an intermediate black hole. It has been dated around 12 billion years old, making it one of the oldest clusters recorded. Although faint, M15 can be spotted with a pair of binoculars and makes great viewing in even a small telescope.