The Stars: July

Low down in the south of July's sky lurks a venomous monster: a mighty cosmic scorpion, riding high in the skies of Mediterranean latitudes. One of the rare constellations that actually resembles its terrestrial counterpart, Scorpius was probably first logged in the Euphrates region around 5,000BC.

How did a scorpion find its way into the sky? It has a lot to do with Orion. The bragging hunter claimed to Artemis – the venerated Greek goddess and Mistress of the Hunt – that he was capable of killing every animal on Earth. But Artemis, who protected her animals, was annoyed by Orion's posturing and sent him a scorpion which stung Orion on the foot – and the mighty hunter was no more. But Zeus, who had been watching the feud, admired the plucky scorpion and had him raised into the heavens. Artemis compassionately asked Zeus to place Orion up there as well. Both constellations are in our skies, but on opposite sides of the heavens: we see Scorpius in summer, and Orion in winter. This ensures that the scorpion can never bite Orion again.

Scorpius is dominated by baleful-red Antares, the sky's fifth brightest star. Its name means 'rival of Mars'. Placed in our Solar System, Antares – 800 times bigger than the Sun – would stretch all the way to the asteroid belt. It's a cool star on its way out, with a temperature of just 3,500C (as compared to 5,000C for our Sun). But it is 10,000 times brighter than our local star.

You can see the top of the constellation from the UK, but if you're in the Mediterranean you'll see Scorpius in all its splendour. At the top right are its three grasping pincers – the stars Acrab, Dschubba and Vrischika. Below lies Antares, the scorpion's heart. Continue sweeping down the beast's spine to find two beautiful young 'open' star clusters, M6 and M7.

Although they're so close that you can see them with the unaided eye, through a telescope they are a glorious sight. Now we reach his upturned tail. It consists of two stars: first Shaula, which means 'raised tail' in Arabic and, finally, there's Lesath: Arabic for 'the bite of a poisonous animal' – as Orion discovered to his cost.

What's Up

There's a celestial lantern to illuminate your barbecues: brilliant Venus, the 'Evening Star', which hangs in the west after sunset and grows brighter during July as this fast-moving planet closes with the Earth on their separate tracks around the Sun. To the left (southwards), you can spot two fainter planets: reddish Mars, and, to the left again, pale-yellow Saturn. Mid-month, the crescent Moonlies beneath each. It's below Venus on 14 July, Mars on 15 July and Saturn on 16 July.

And if your barbecue carries on after midnight look out for the second brightest planet, Jupiter, which rises in the east after Venus has set in the west. The Moon lies near this mighty planet on 4 July and again on 30 July.

There's a total eclipse of the Sun at the time of the New Moon on 11 July, but – sad to say – nothing of this event is visible from the UK. You'll have to be in the South Pacific, French Polynesia, Easter Island or Patagonia to witness this awesome sky sight.

Diary

6: Earth at aphelion (furthest from Sun)

11: 8.40pm New Moon; total solar eclipse (not visible from UK)

18: 11.10am Moon at First Quarter

26: 2.36am Full Moon