See the return of the Andromeda Galaxy


This picture of the Andromeda Galaxy, Messier 31, also shows its satellite galaxies, Messier 110 (top) and Messier 32 (lower right of M31’s nucleus). Dust lanes among the spiral arms of M31 can be seen in large unprofessional instruments, but the bright nucleus, M32 and M110 are easy objectives for little telescopes. A 65mm f/6.5 refractor and Canon 1100D DSLR were used to take this portrait of our biggest galactic neighbor from rural Norfolk on 29 November 2013. Magnitude +4.5 nu (ν) Andromeda is the blue star in the lower left. Image credit: Ade Ashford
Because the British Isles are no longer experiencing twilight all night, now keen observers are already looking forward to the ‘season of mists and mellow fruitfulness’ with its gloom skies at a friendly hour. Is it now too soon to be thinking of autumn? Probably, but the equinox is almost five weeks away.
Approximately 2.5 million light-years away, M31 is often estimated as being the most distant object that we can see with the unaided eye on moonless nights from positions free of light pollution. Approximately 220,000 light-years in diameter, M31 is a spiral galaxy about 1.5 times larger than our galaxy, making it the greatest member of the Local Group. M31 could contain a trillion stars.
Star-hopping to the Andromeda Galaxy
If you want to see M31 over the next few nights about 11 pm, you will need a clear eastern horizon away from the glare of streetlights. The Moon is presently a young waxing crescent and will not become obtrusive in UK skies until around Thursday, 20 August. A pair of 8×40, 10×50 or 7×50 binoculars will be a good help, if you own or only borrow a pair.


For the Andromeda Galaxy, Mid-August is open season, or M31 — maybe one of the best deep-sky objects for Northern Hemisphere observers. This is a quadrant of the sky centered on the E-NE horizon as seen from the UK on 15 August at 11 pm BST, or 9 pm by the middle of September. The panorama is 90 degrees wide, or 4 times the span of an outstretched hand at arm’s length. The 10×50 red circle represent the field of view of a typical 10×50 binocular for scale. (For a larger view click the graphic.) Image credit: Ade Ashford.
The starting point of our star hop to M31 is the star of the square — magnitude +2 star Alpheratz. In a 10×50 binocular, you need to move three fields of view to the left, passing magnitude +3.2 star delta (δ) Andromedae, until you reach magnitude +2 star Mirach.


Image credit: Ade Ashford

Once you are convinced that Mirach is in your sights, you need to move ‘up’ about one-and-a-half binocular fields to find the diffuse oval glow that is our destination. Fortunately, there is a convenient line of guide stars — magnitude +3.8 mu (μ) Andromedae and magnitude +4.5 nu (ν) Andromedae — to direct us to M31.

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