JULY sees the logical progression from spring groups such as Leo and Virgo, which are now setting in the west, to summer constellations. The first stars of Pegasus are beginning to appear in the east after midnight. It is rather unfortunate that the southern part of the sky will be composed of large faint groups. At least Antares in Scorpius is visible, shining low down in the south, and overhead we have the ‘Summer Triangle’ of stars; Vega, Deneb and Altair. The Plough is still very high up but is now to the west of the overhead point which means that Cassiopeia is now higher in the north east. Arcturus in Bootes is still very much in evidence, but Spica in Virgo is now very low in the west. The summer triangle will dominate the summer months of stargazing. If you look overhead you will see a bright bluish looking star which is Vega, the brightest star in the constellation of Lyra (the Lyre). The rest of Lyra is made up of a quadrilateral of fairly bright stars. A line drawn to the left will reach a bright star at the top of a very large cross shape of stars. This star is Deneb, the brightest star in the constellation of Cygnus (the Swan). Cygnus is often referred to as ‘The Northern Cross’ because of its shape. If two lines are drawn from Vega and Deneb downwards they will reach a bright star lower down in the south. This is Altair, in the constellation of Aquila (the Eagle). The summer triangle gives an opportunity to show that sometimes appearances can be deceptive when it comes to brightness of the stars. If we compare Altair, Deneb and Vega, we see that Vega is clearly the brightest, followed by Altair then Deneb. This, however, does not take into account how far away the stars are from the Earth. When we discover that Altair is 17 light years away, Vega is 25 light years away and Deneb is 2,600 light years away, we see that although Deneb appears the faintest of the summer triangle stars it really is the brightest, only appearing faint because it is very much further away. The southern part of the sky is now dominated by three large faint groups; Hercules, Ophiuchus (the Serpent Bearer) and Serpens (the Serpent). Very low down in the south is the bright red star Antares, the brightest star in Scorpius (the Scorpion). Antares is often referred to as ‘The Rival of Mars’ due to its bright red colour. In Greek mythology Orion boasted that he could kill any living creature and one day while bragging to a large crowd of people about all the animals he had killed, he did not see a little scorpion creep up behind him. The scorpion stung him on the ankle and killed him. The gods were impressed by Orion’s boasting so they placed him in the sky. The also put the clever scorpion in the sky. To make sure that they could never meet again they placed Orion in the winter sky and the scorpion in the summer sky.

What’s up in the Solar System?

The planets in July

Mars and Saturn are both visible low in the south. Mars looks very red but through the month we will see it get a little bit fainter as the planet moves further away from us. Saturn, also low in the south, is to the left of Mars and appears as a bright yellowish looking ‘star’. Beneath both Mars and Saturn and forming a triangle is a real red star, Antares.

Jupiter might just be glimpsed very low in the west after sunset, while Mercury and Venus are still too close to the Sun to be seen.

Meteor Showers

Around July 28 or July 29 the annual peak of the Delta Aquarid meteor shower will occur. It might be possible to see up to 20 meteors per hour. The best time to see this shower will be between midnight and dawn. Delta Aquarid meteors may come from Comet Machholz which was discovered by Donald Machholz in 1986. Comets are like dirty snowballs travelling around the solar system; they leave a trail of dust behind them and if the earth happens to pass through this trail then we see a meteor shower. Meteors, or as they are often called, ‘shooting stars’ have nothing at all to do with stars, but are tiny grains of dust burning up as they enter the earth’s atmosphere. Next month of course we will see the Perseid meteor shower, which is one of the most splendid of the year.

Highlights for the Moon in July

July 12: first quarter moon near Spica

July 14, 15 and 16: near full moon close to Mars, Saturn and Antares

Phases of the Moon for July

New Moon July 4, First Quarter July, 12, Full Moon July, 19, Last Quarter July, 26

This month’s full moon is called the ‘Thunder Moon’. This is the month when warmer weather brings the potential for violent thunderstorms.

Earth at Aphelion

The Earth will be at Aphelion, or furthest point from the Sun, on July 4 at 5pm, when it will be 95 million miles from the Sun. The Earth orbits the Sun not quite in a circle but in an egg shaped path or an ellipse, which means that it gets closest to the Sun in January and furthest away from the Sun in July. It may seem strange that we are further away from the Sun in summer, but the seasons are determined not by how near or far the Earth is from the Sun, but by which hemisphere is tilted towards or away from the Sun.

The next meeting of the Earby Astronomical society will be on Friday, July 22 at All Saints’ Church, Earby from 7.30pm to 9pm. The talk will be entitled ‘Mars and Saturn’ and will be presented by Martin Lunn MBE FRAS, Earby Astronomical Society.