We’ve had some clear evenings so I hope you have been making the most of them.
The following chart represents the night sky at 11.00pm BST on the 8th of October and at 10.00pm BST on the 23rd October. To use the chart, face your southern horizon at the appropriate time and you will see the stars in the chart.
We discussed the Great Square of Pegasus last month and we shall be using that as our starting point this month. Probably easier to start by locating Cassiopeia near your zenith then scanning down to find the Great Square of Pegasus. The brightest star in the square is Alpheratz in the top left hand corner and as mentioned last week it actually belongs to the constellation Andromeda- Princess Andromeda, daughter of King Cepheus and Queen Cassiopeia in Greek mythology. The main features of Andromeda are two curved strings of stars, extending to the left of Alpheratz, the lower of which stands out more with the presence of two stars, Mirach and Almach, of around magnitude 2 while the upper curve of stars is fainter with stars of magnitude 3 to 4.5. Also, Cassiopeia is just above it and to the east. Fortunately some of the brighter stars form natural pairs with the fainter stars making the latter fairly easy to locate. The constellation Andromeda is home to one of the most famous objects in the night sky- the Andromeda galaxy also known as M31 and shown on the chart by a red X labelled M31. The Andromeda galaxy is visible to the naked eye (apparent magnitude m = 3.4) but good conditions are required and it helps if you know exactly where to look. From Alpheratz, jump to the second pair of stars along the curved strings and extend a line from Mirach through the fainter star and the Andromeda galaxy will be at a distance approximately equal to the distance between the stars. Don’t expect to see a beautiful coloured spiral galaxy like you see in images from the Hubble or the James Webb telescopes, more of a smudge or fuzzy star. Nevertheless the fact that you are looking at the most distant object that you can see with the unaided eye at a distance of two and a half million light years (that means that the light entering your eye set out from Andromeda two and a half million years ago) should give you a sense of achievement and some wonder.
Below and to the left of Andromeda is the constellation Triangulum- The Triangle. There is not much to say about it because its brightest star is only magnitude 3 but at least it looks like a triangle and because it is compact it is easily picked out.
We have two zodiacal constellations to finish with, Aries- The Ram and Pisces- The Fishes. Both are pretty inconspicuous but Aries represents the golden fleece in Greek mythology and its claim to fame is that over two thousand years ago the vernal equinox lay on the border of Aries and Pisces and it is still referred to as the First Point of Aries. Since then, because of the precession of the Earth in its journey round the Sun (it wobbles very slowly like a spinning top), the vernal equinox has moved through Pisces towards Aquarius. Aries contains only one reasonably bright star, Hamal, a yellow giant of magnitude 2.
Pisces has no stars brighter than magnitude 3.6 so doesn’t have much to offer other than a distinctive ring of seven stars known as the Circlet lying below the Great Square of Pegasus.
Something to look out for
On Monday the 2nd October there will be a close approach of the Moon and Jupiter, low in the east just after they rise about 8.00pm BST but the later you leave it the higher in the sky they will be. This will be repeated on Sunday 29th October but by this time Jupiter will be rising about two hours earlier so there will be easier viewing all evening.
On Saturday 14th October there is going to be an annular solar eclipse but visible only in the Americas and even then only to a few but watch out for it on the news.
For the early birds amongst you Venus will be at its highest altitude in the morning sky on Wednesday 18th October, rising four hours ahead of the Sun (sunrise about 7.30am BST) and shining brightly at magnitude -4.4 well above the horizon.
Finally there will be a close approach of the Moon and Saturn on Tuesday 24th October visible above the southern horizon and at its highest altitude about 9.00pm BST.
Don’t forget that British Summer Time finishes on Sunday 29th October, remember to put your clocks back 1 hour.