Sunday, 18 October 2015

Astrognome Astronomy Andromeda


Linked with Pegasus is Andromeda, the princess of the legend in which Perseus, Cassiopeia, Cepheus and Cetus all have important roles. Andromeda’s main stars are arranged in a rough line of stars from the square of Pegasus towards Perseus. 

Alpha or Alpheratz is the ‘stolen’ star from the square of Pegasus is of magnitude 2.1 then moving towards Perseus from Alpha there is Delta magnitude 3.2, Beta magnitude 2.0 and Gamma magnitude 2.1.

The most famous object in Andromeda is Messier 31 (M31) the Andromeda Galaxy.  This is the most distant object that can be seen with your eye without using an optical aid!! M31 is around 2.2 million light years away.

To find M31 locate Beta or Mirach then look upwards towards two fainter stars Mu magnitude 3.9 and Nu magnitude 4.4.  The Andromeda Galaxy lies close to Nu. If you struggle with very dark observing sites M31 can easily be seen in binoculars.

It was only after World War 1 that astronomers realised that the Andromeda Nebula as it was known as was not in our galaxy. It was a galaxy in its own right.  It was Edwin Hubble in 1923 that realised that the Andromeda Galaxy might be about 750,000 light years away. This figure was re defined in 1952 by Walter Baade to be about 2.2 million light years.

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