Brian Jones: Pegasus
According to Greek legend, Pegasus was the son of Neptune and Medusa. When Perseus slew Medusa, Pegasus sprang from her decapitated body and flew away, eventually reaching Corinth where he was found by Bellerophon, the son of Glaucus. Bellerophon tamed Pegasus and used him in his fight against the fire-breathing monster Chimaera. After enjoying many other adventures with Pegasus, Bellerophon eventually decided to try and fly to Olympus, the home of the gods. On the way, Pegasus threw Bellerophon and completed the journey alone. Zeus, the ruler of Olympus and god of sky and thunder, eventually placed the winged horse in the heavens where we see him today.
The constellation contains no really bright stars, although the Square of Pegasus is fairly easy to locate, situated roughly two-thirds of the way up from the southern horizon to the overhead point during mid- to late-evenings in October. Once the Square of Pegasus has been identified, the rest of the group can be picked out towards the west.
The first interesting point to note is that Sirrah, the star marking the north-eastern corner, is actually a member of the adjacent constellation Andromeda (see next month’s blog), and is only ‘borrowed’ to complete the Square of Pegasus on star charts.
Below Sirrah, and denoting the south-eastern corner, can be found Algenib, the name of which is derived from the Arabic for ‘wing’ or ‘side’. Algenib is a blue-white star, similar to Markab which marks the south-western corner of the Square of Pegasus, Markab is found to the west of Algenib and situated in an area of sky devoid of bright stars. It’s name is derived from the Arabic for ‘shoulder’ whilst that of Scheat, located at the north-western corner of the Square, comes from the Arabic for ‘shin’.
Marking the horse’s head is Enif, a name translated from the Arabic for ‘nose’, although Arabic astronomers themselves sometimes referred to this star as the horse’s mouth. Enif is fairly remote, its light having taken something like eight centuries to reach us. Much nearer are Homam, meaning ‘lucky star of the hero’ and Matar, from the Arabic for ‘the fortunate rain’. Homam lies at a distance of a little over 200 light years while Matar is around 360 light years away.
A little to the north-west of Enif can be found the beautiful globular star cluster M15, discovered by the Italian astronomer Giovanni Domenico Maraldi in 1746 and located at a distance of almost 40,000 light years. The accompanying finder chart may prove useful in helping to locate the cluster, although it can be detected by carefully sweeping the area with a pair of binoculars, providing the sky is dark and clear. Once found, the cluster should appear as a small diffuse patch of light, telescopes being needed to resolve any individual stars.
Pegasus lies in a fairly barren area of sky, and it is an interesting exercise to try to count the number of naked-eye stars within the Square. Those with really keen eyesight may be able to spot around two dozen, although dark, moonless skies are essential for the best results.
Pegasus played a prominent role in Greek folklore, and the constellation depicting this wonderful winged horse certainly plays an important part in our autumn night sky. Happy stargazing!