Night sky with Martin Lunn: July's spectacular Super Moon

When the Moon rises on July 3 it will be closer to the Earth than normal, and consequently will appear to be seven per cent larger than usual. This will make it a spectacular sight. If the weather is cloudy on the day don’t worry because there will be two in August and another in September.

The July supermoon will be 224,895 miles (361,934km) from the Earth. One of the supermoons in August will actually be the closest one to us.

This is the month when the Earth is farthest from the Sun. July marks the second half of the noctilucent cloud season, and the first of the major summer meteor showers can be seen this month. The skies from mid-month will start to become darker, allowing us to see the summer stars more easily.

On July 4, the Earth is at aphelion, or farthest point from the Sun, on its yearly orbit. At aphelion Earth will be 94.5 million miles (152 million km) from the Sun. In the northern hemisphere we are now experiencing summer.

In January however, the Earth was at Perihelion, or closest to the Sun, being only 91.3 million miles (147 million km) away. The seasons are caused not by how close the Earth is to the Sun, but by which hemisphere is tilted towards it. In July the northern hemisphere is tilted towards the Sun, while in January when the Earth is closest to the Sun, the northern hemisphere is tilted away from it.

I talked about noctilucent clouds last month. There have already been some good sightings of the noctilucent clouds in other parts of the world, and with the upper part of the atmosphere, the Mesosphere, being incredibly cold, there is a very good chance that these magical clouds will be seen from Britain this month. ‘Noctilucent’ is Latin and it means ‘night shining’. Remember to look to the north after sunset.

In July the Summer Triangle stars Vega, Deneb and Altair are at their best.

If you look directly overhead the bright star you see is Vega, in the constellation of Lyra the Lyre, which is a small but distinctive constellation. Look to the left of Vega and you will see the star Epsilon Lyrae which is a famous double star.

On a clear night people with reasonable sight should be able to see that the star is made up of two stars side by side. In a telescope each of the component stars is itself a double star so we could refer to it as a 'double double' or quadruple star.

The rest of Lyra is made up of a quadrilateral of stars with Beta, at the bottom right of the quadrilateral, being a variable star that was discovered to vary by the deaf astronomer John Goodricke in York in 1784.

Deneb is the brightest star in Cygnus the Swan, which is sometimes referred to as the Northern Cross. The stars are spread out over a much larger area and are fainter than those in Lyra but once you have located Cygnus you will easily recognise it again.

It lies in the milky way so there are many, many stars to see in this part of the sky, particularly if you use binoculars. At the end of the cross shape is the star Beta Cygni or Albireo. Seen through binoculars or a small telescope it is one of the most glorious double stars, made up of a blue star and a yellow star.

The third member of the summer triangle is the most southerly; Altair, in the constellation of Aquila the Eagle. The constellation does look a little bit like an eagle in the sky. It has, like Vega, a connection with York, because the star called Eta is variable and was discovered by Edward Pigott who worked in York with John Goodricke.

Both Beta Lyrae and Eta Aquilae were discovered on September 12 1784, which was a night to remember as far as astronomy is concerned. In fact, Goodricke and Pigott contributed so much to variable star astronomy in the brief time they worked together from 1781 until 1786 that I refer to them as 'the fathers of variable star astronomy'.

The Summer Triangle shows us that appearances can be deceptive. When we look at the three stars that form the triangle, Vega appears much the brightest, Altair and Deneb appearing significantly fainter, but when we consider how far away they are, a different picture appears.

Altair is a mere 17 light years away, Vega a slightly more distant 25 light years, but Deneb, which appears the faintest, is 2,500 light years away. This means that if they were all placed at the same distance from the Earth, Deneb would massively outshine the other two stars.

Another bright star that can be seen in the summer months, this time very low down in the south, is Antares in the constellation of Scorpius the Scorpion, sometimes known as 'the rival of Mars' because of its colour. Unfortunately, because Antares is so low in the sky when seen from Britain, it never rises high in the sky.

To see it at its best you would need to be in the Mediterranean area. It is a red supergiant and in fact so big that the orbits of the four planets closest to the Sun: Mercury; Venus; Earth and Mars, would comfortably fit inside Antares.

Apart from the Summer Triangle stars and Antares, a large part of the southern aspect of the sky this month is occupied by the large and formless constellations of Hercules, Ophiuchus the Serpent Bearer and Serpens the Serpent.

As for the more familiar groups of stars, the Plough is still high in the north west, which means that the 'W' of Cassiopeia has now become a little higher in the north east.

The Planets in July: This is the last chance to see Venus or the ‘Evening Star’ in the summer sky this year. It has been visible for many weeks now and at the start of the month sets at around 11pm, however by the end of the month Venus is too close to the Sun to be seen. In the morning sky around 1.00am Jupiter appears as a bright white dot in the south-east, it will be easy to see in the evening skies later this year. At around midnight low in the south-east you can see a fairly bright yellowish looking ‘star’. This is the planet Saturn. It will become easier to see later in the year.

The other naked eye planets Mercury and Mars are too close to the Sun to be seen this month.

Meteor Showers: The first of the summer meteor showers is the Delta Aquarids which can be seen on the night of the 30th. These meteors, or shooting stars as some people call them, are the remains of comet Macholz. Around 15 meteors per hour can be seen.

Phases of the Moon for July: Full Moon 3; Last quarter 10; New Moon 17; First Quarter 25.