As promised Jupiter and Saturn are now in the late evening sky and they are on the diagram below but with Jupiter shining so brightly in the southern skies it doesn’t need a signpost. The highlight of last month was the appearance of the comet Neowise visible to the unaided eye in the northern sky and Josh Dury gives a description of where to look for it in his recent e-mail, ‘Identify the constellation, Ursa Major, and use the two stars marking the edge of the saucepan to draw a line at about a similar distance until you come across a faint, smudge patch in the sky. This is Comet Neowise’. It is not usually wise to predict when a comet will appear because over the years there have been many disappointments because of unfulfilled promises of a spectacular sight. One comet which did live up to and even exceed expectations was comet Hale-Bopp back in 1997 and I remember it well. I mention it because it was discovered by amateurs.
We talked about the Summer Triangle of Vega, Deneb and Altair last month so we will start from there. From Altair in the Summer Triangle, looking southerly, drop down the Milky Way close to the horizon and to the right is the constellation Sagittarius (the Archer) which lies on the ecliptic to the left of Scorpius. Yet again it is hard to distinguish the archer of mythology but what is easily recognisable is the asterism ‘the Teapot’. The planets Jupiter and Saturn are on the diagram and in fact Jupiter is by far the brightest object in that part of the sky and you cannot miss it. Sagittarius lies in the direction of the centre of our Milky Way. There are dense clouds of gas and dust along the plane of the Milky Way which obscure our view to the centre. See the recent picture of the Milky Way sent back by my granddaughter from New Zealand.
To the right of Sagittarius and also close to the horizon you will see the star Antares which we mentioned last month.
Now let us go to the other end of the Summer Triangle with Vega and Deneb and look at two circumpolar constellations. Face south and look up to find Polaris- the pole star. Obviously it is above your zenith so you need your deckchair again! If you look to the east you should recognise the ‘W’ shape of the constellation Cassiopeia which we found previously from the Plough via Polaris. So do the reverse trip from Navi through Polaris and you come to the Plough. You will see it is almost upside down now. Just as we have watched the Plough change its orientation so we can enjoy watching Cassiopeia continue on its anticlockwise journey around the pole star gradually taking on the proper ‘W’ shape we are accustomed to during the rest of the autumn as it heads south. Just east of Cassiopeia is a group of not very bright stars forming a shape roughly similar to the gable end of a house. This is the constellation Cepheus (King Cepheus of Ethiopia in ancient mythology and husband of Cassiopeia). Perhaps its claim to fame is that it contains the prototype of an important group of variable stars called ‘cepheid variables’ which have been fundamental in establishing a ‘standard candle’ for the measurement of intergalactic distances and the rate of expansion of the universe- a key area of research in cosmology at present. The prototype was delta Cep in the bottom left hand corner of the house shape.
I guarantee you will enjoy seeing Cassiopeia in the southern skies for the rest of the year.
Something to look out for
At the beginning of the month on Saturday 1st there is a close approach of a near full moon and Jupiter with Saturn just to the east. There is another close approach on Friday 28th August. We cannot all be together for the Perseid meteor shower as usual but if you want to see some shooting stars look out on the nights of 11th and 12th August and be prepared to stay up a little longer than usual to give yourself the best chance in spite of a Last Quarter Moon.