WHAT’S THE STORY?

IN the next few days leading up to its peak on August 12, the Perseid meteor shower will make its annual appearance in the skies above Scotland.

This summer display of cosmic brilliance is a hit with astronomers and the general public alike, because there is usually a very impressive number of meteors – sometimes known as shooting stars – visible to the naked eye, in the Northern Hemisphere in particular.

As they skip across the Earth’s atmosphere at 130,000 mph, the Perseids usually leave long bright trails, but occasionally one will plunge to Earth creating an even more spectacular fireball.

All that is usually required to see them is a clear sky, a dark place to observe them from, and patience. This year it is predicted that 50 to 100 meteors per hour will be visible at peak times.

WHAT EXACTLY ARE THE PERSEIDS?

BEFORE they hit the Earth’s atmosphere, the Perseids are known technically as meteoroids, and when they start to burn up – the shooting star effect – they are meteors. Only in the unlikely event of one failing to burn up and thus falling to earth does a meteor become a meteorite.

The Perseids are the detritus left behind by the Comet Swift-Tuttle, so named because the comet was observed by two American astronomers, Lewis Swift and Horace Parnell Tuttle, within three days of each other in July, 1862 – the latter gentleman broke off from fighting the Confederates in the American Civil War to make his observation.

The comet had been around for a lot longer before Swift and Tuttle observed it. Its orbit has been calculated at 133 years, and signs of the comet in literature and art go back more than 2000 years to ancient China who were the kings of written astronomy while the people in Scotland at the time built their astronomical records in stone circles and other spectacular signposts.

Swift-Tuttle is the largest comet known to regularly come near to Earth – near being a relative term as its next passage will see it “scrape” by our planet at a range of 15 million miles.

Thankfully its orbit is pretty steady because, with a nucleus about 16 miles wide, Swift-Tuttle could do very serious damage to us all if the comet was to hit Earth. That won’t happen for at least 2000 years, you will be glad to know.

The comet’s last pass by Earth during its orbit around the sun was in 1992, and its next will be in 2126, but every year, Earth passes through the dust and debris it leaves behind, and it is that detritus which gives us the annual Perseid meteor shower.

They get their name from the fact that the meteors tend to appear from the vicinity of the Perseus constellation, their “radiant” in technical terms. For the mythologically uninitiated, Perseus was the son of Zeus and the mortal woman Danaë, and he is most famous for slaying Medusa the Gorgon and having a winged horse called Pegasus.

WHEN AND WHERE CAN WE SEE THEM IN SCOTLAND?

EARTH will pass through the path of Comet Swift-Tuttle until August 24, and already there have been some sightings of meteors. The shower’s peak, however, is this week when our planet passes through the dustiest area of Swift-Tuttle’s debris.

Peak viewing time in Scotland occurs in the early hours of August 12. Most experts say just before dawn when the sky is at its darkest is the best time to see them, but any time after midnight should see the Perseids start to appear. There are exact charts online to show where best to look for them, but for most Scots simply looking between the “radiant” in the North East and the “zenith” straight above you should get you a sighting.

ISN’T VIEWING DEPENDENT ON THE WEATHER?

BELIEVE it or not, sometimes the meteors can be seen through light cloud, though obviously a very dark cloudless night is best.

Across Scotland there are now a number of designated Dark Discovery sites which are perfect for viewing the night sky – you can find information at www.darkskydiscovery.org.uk or just visit Moffat, the first official Dark Sky town in Scotland.

Unfortunately the Moon will be bright later this week, and that may affect the chances of seeing any meteors.

As for the cloud cover – hard to say at this point, but the Met Office are predicting light cloud at night later in the week. Of course it all depends on whether you believe in long range weather forecasts, which in Scotland is something of a contradiction in terms since we often have Vivaldi weather – four seasons in one day – that nobody can foresee in the short term, never mind weeks ahead.

Fingers crossed for a break in the clouds, and happy meteor hunting.