The summer solstice has passed now so we will gradually get improved lighting conditions for observing. The notes here apply at 11.00pm BST at the end of the first week of the month and at 10.00pm BST at the beginning of the last week in the month. However I find that at present the sky doesn’t really get dark until after midnight and this month you will need a clear view to the southern horizon with no obstructions and free from local light pollution. I did have a look out on the morning of June 19th to see the close approach of Venus and the Moon but I’m afraid the cloudy skies were against me.
Back at the beginning of April if you looked directly above you while facing south, the Plough was directly overhead (at your zenith) and looked like a plough. Now you will notice that it has moved anti-clockwise about the North Pole and is now upright on its handle. Keep checking the orientation of the Plough as the year progresses.
So while facing south, look directly above you and just before your zenith you will see a very bright star. Perhaps this is the time to get your deckchair out and lie flat on your back! This star is easily recognisable due to its brilliance and a grouping of four stars to its bottom left hand side. These stars make up the compact constellation Lyra (the Lyre or Harp) and the bright star is Vega, alpha Lyr, the 3rd brightest star visible from the northern hemisphere. The lighter region of the diagram to the left of Vega represents the Milky Way, the star filled disc of our galaxy, and there you find a giant cross in the sky and this is the constellation Cygnus (the Swan) with the bright star Deneb, alpha Cyg, representing the tail of the swan which is flying down the Milky Way. Deneb is the 14th brightest star visible from the northern hemisphere. At the head of the long neck is the star Alberio, beta Cyg, about which I have heard our chairman, Hugh, wax lyrical on more than one occasion so do look at it through a telescope if you get the chance.
Now face Vega and Deneb and drop down about halfway to the horizon till you find the star Altair in the constellation Aquila (the Eagle). Altair, alpha Aql, is identified by two fainter stars either side of it and together they point to Vega.
I hope you have been keeping count of these bright stars because Altair is the 8th brightest star visible from the northern hemisphere and you have now become acquainted with eight of the eighteen brightest stars. These three stars Vega, Deneb and Altair form what is called the Summer Triangle depicted in yellow in the diagram. The Summer Triangle is something you will be able to enjoy looking at for the rest of the summer into autumn. Like the Plough it is a big help in finding your bearings.
Now let us be a little more subtle because biggest and brightest isn’t always the best. Last month we found Arcturus by following round the arc of the handle of the Plough. Between Vega and Arcturus you find the constellations Hercules (the strong man from Greek mythology) and Corona Borealis (the Northern Crown). Hercules is a fairly faint constellation and looks more like flailing windmill blades than a strong man but the most distinctive feature is the four central stars in the shape of a quadrilateral forming an asterism known as the Keystone. Corona Borealis is small but distinctive, consisting of seven faint stars in a horseshoe shape if you cannot envisage a crown.
We are quite unashamedly going back to bright star ‘bagging’. We are doing this because the object in question is best observed in summertime. Imagine a line from Vega to Arcturus and from its midpoint follow a line to the horizon between Hercules and Corona Borealis until you see a reddish star. Remember you will need a good unobstructed view to your southern horizon. This star is Antares, the brightest star in the constellation Scorpius (the scorpion) and is the sole attraction because most of Scorpius and specifically its fish-hook shaped tail is not visible from our latitude. Antares is the 10th brightest star visible from the northern hemisphere and that is because it is a red supergiant and if it were to replace our sun, its surface would lie between the orbits of Mars and Jupiter. That is big! It is said to represent the heart of the scorpion.
Something to look out for
The major planets, Jupiter and Saturn, return to the late evening sky this month quite close together and visible all night. On July 14th Jupiter will be at opposition, on the opposite side of the Earth from the Sun, so will be at its closest and brightest. A week later on the 20th July, Saturn reaches opposition but unfortunately both planets will be quite low in the southern sky and although bright are not ideally located for good viewing.