Are you up for a free ‘firework show’ from Space? If so, this is the month for you because on the 11th August (Tuesday), the Perseids Meteor Shower is coming to town! As our planet silently glides through the cold void of the Solar System (at the phenomenal speed of 30 kilometres per second) it is currently approaching the trail of a comet; Comet Swift-Tuttle. Comets are ancient celestial bodies commonly referred to as “large, dirty snowballs in Space” and can have a solid nucleus measuring upwards from around 750 metres in diameter. Named after American astronomers Lewis Swift and Horace Parnell Tuttle that discovered it in 1862, this periodic comet (a comet that returns every 133 years to fly past the Sun) lies in the upper end of the size range, measuring 26 kilometres across.
Resting on Northern Ireland, it would completely hide the land area between Belfast and Lurgan. As the comet continues on its orbital journey, solar radiation melts and vaporises pockets of ice in the comet’s nucleus whilst also releasing any dust trapped within. This forms an enveloping cloud around the comet nucleus up to 15 times the diameter of Earth, called the coma. Behind it, trailing up to 10 million kilometres across the Solar System is a dust tail, and it crosses Earth’s orbital path around the Sun.
So what can we expect on the night of the 11th-12th August? Well for a few evenings running up to the 11th is the ‘dress rehearsal’ before what is anticipated to be the peak of the main event for those in the Northern hemisphere, promising anywhere between 60 to 100 meteors in an hour! The best bit is, it’s FREE! And you don’t need any fancy astronomical viewing equipment either, just keep your eyes wide open.
What time? Simples – after dark! So at this time of year, you might want to take just one more coffee so you can start looking up from 11pm (on the night of the 11th) until 4 am on the morning of the 12th to see the Perseids’ fiery display. Although tiny, no bigger than grains of sand, the particles from Comet Swift-Tuttle will go out in a blaze of glory approximately 60 kilometres up, catching fire from frictional heat as they rub against Earth’s atmosphere. The Perseids, like all meteors can enter Earth’s atmosphere at speeds of up to 250 000km/hr.
What part of the sky? To know you’re looking in the right direction, look to where the Sun rises in the morning (roughly East), move your eyes a little to the left (looking north-east) and then roll them upwards. Look out for that bright ‘W’-shaped dot-to-dot pattern of stars, Cassiopeia, and you know you’re in the correct expanse of sky. Drop your eyes and just beneath her you’ll be looking where you want to be, at the constellation of Perseus.
In Greek mythology Perseus was the son of Zeus and heroic rescuer of the beautiful Princess, Andromeda. In the heavens though, Perseus doesn’t look quite so spectacular, at best perhaps, like a stick figure drawing by a child (depending on interpretation!) None-the-less as it is Perseus’ celestial territory from which the meteors will radiate, they take his name. If for some reason you find yourself wishing for some additional cosmic signage to the beautiful silent spectacular, from midnight, the Moon will rise to help, as it will appear almost directly beneath the meteor shower and provide a useful reference point. However, as the Moon is the brightest celestial object of the night sky it may outshine the main event, so be ready to block its gleam with your hand to stand a better chance of seeing the more discreet cosmic visitors.
If you miss the ‘peak night’ the good news is that you may still glimpse Comet Swift-Tuttle’s meteors for a few more evenings on repeat after the 11th August. Let’s hope for some clear skies!