THE AUTUMN NIGHT SKY
VIEW OF THE SKY LOOKING SOUTH AT 9:00 pm ON 1st OCTOBER
Andromeda and Pegasus are two constellations joined at the star Sirrah which although actually part of Andromeda appears to be more a part of the great square of Pegasus. Pegasus is the easiest to find of the two but once found it easily leads to Andromeda. However Andromeda can be found directly by using the two ‘Vs’ of the ‘W’ shape of Cassiopeia as pointers to it.
Andromeda is not impressive to look at but it does contain some very important and beautiful objects. The most important is Messier 31 (M31) or (NGC224) The Great Spiral Galaxy. This is actually almost a twin sister of our own Milky Way galaxy (which can be seen as a hazy patch crossing the chart above), forming what is called our ‘local group’ of about 20 nearby galaxies. It is a gigantic swirling cloud of about 2 thousand million stars. Because we are viewing M31 almost side on it looks like a hazy elliptical patch with a brighter circular patch at the centre. If we could see M31 from the top or bottom it would be like a whirlpool with spiralling arms curving out from the central ball of stars. Each speck of light making up the hazy cloud is a star like our sun. Light from M31 takes 2.3million years to reach us and is the most distant object that can be seen with the unaided human eye.
Close to M31 is a satellite galaxy called M32 or (NGC225). This is a smaller elliptical galaxy associated with M31. Our own galaxy also has its own satellite galaxies. Two of them, known as the Magellanic Clouds appear like islands separated from the Milky Way when seen from the southern hemisphere of earth.
To find M31 first locate the line of three stars forming what appears to be a handle attached to the top left star of the square of Pegasus this is Andromeda. From the centre star (Mirach) of this line of three stars there two fainter stars forming another line above the first but at a right angle. Follow this second line up and just above and to the right of the furthermost star is a hazy patch, this is M31. On a clear moonless night you may be able to see M31 with your unaided eye but binoculars should show it quite clearly.
Pegasus is larger in the sky than most people expect it to be but once found it is easy to find again. It really has only four bright stars of which the top left one forming the square is actually part of Andromeda. The centre of the square has about five stars that can be seen with the naked eye but these are quite dim and moonlight will blot them out.