A little ramble through the winter sky - Perseus

 Perseus was the hero of Greek mythology who rescued Andromeda who was chained to a rock waiting to be eaten by the Kraken sea monster.  Previously he had killed the medusa.  The Gorgons eye is marked by Algol. Perseus lies in a rich part of the milky way and is worth sweeping with binoculars.

The pattern of stars that forms Perseus looks rather like an upside letter Y and is seen under another group of stars that form a letter. This is Cassiopeia which forms the letter W.

Every August we can see one of the most spectacular meteor showers of the year. This is the Perseid meteor shower. It is so named because all the meteors appear to come from a point in Perseus that is referred to by astronomers as the Radiant point of this meteor shower. All meteor showers are named after the constellation that they appear to come from.

Alpha or Algenib which means side or is sometimes known as Mirfak the elbow. It has a magnitude of 1.8 and is a F class supergiant with a surface temperature of 6,300 degrees making it hotter than our Sun, Algenib is 510 light years away.

The most famous star in Perseus however is Beta or Algol which means the winking demon. This is an eclipsing binary star that John Goodricke studied from York between 1781 and 1786.

 In 1782 he realised that Algol was made up not of one star but of two stars. He also realised that these stars were eclipsing each other causing Algol to change in brightness. The eclipse occurs every 2.8 days and the magnitude varies between 2.2 – 3.5. Goodricke did not discover the variability that was done by the Italian astronomer Montanari in 1669. Algol lies at a distance of 90 light years and has a surface temperature of 13,000’C and is a B class star. The star which is eclipsing Algol cannot be seen with the eye.

NGC 869 and NGC 884 Mag 3.7 the famous double cluster in Perseus can be seen with the naked eye. These are open clusters with 350 and 300 stars respectively, lying about 7,600 light years away and about 300 light years apart.   NGC 869 and 884 are of magnitude 3.7 and 3.8 respectively, which in binoculars resolves into a grand pair of bright stellar star fields. Each cluster contains over 300 blue white super giant stars. They are about 7,500 light years away. The letters NGC Stand for the New General Catalogue that was introduced in 1895 to catalogue star clusters and galaxies.

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