Even with the full moon there's hope left in the Perseid meteor shower
Distance travelled ~ 569'660'800 km
(Mark Thompson is the BBC One Show's Astronomer and when not reporting for them, he is most likely writing about the sky or looking at it! You will often find him zooming in on, or through it, as not only is Mark an enthusiastic astronomer but he is also a qualified pilot. January 2011 saw Mark as part of the successful BBC Stargazing Live Presenting team. He also regularly writes for Discovery.Com and a host of other astronomy and space websites and will be producing a monthly space watch blog for 23 Degrees.)
It may not seem like it but the Earth is hurtling around the Sun at the breakneck speed of about 107,000 km per hour. We don't often get a chance to see evidence of this motion but around the middle of August every year, something happens which gives it away. Planet Earth passes through a field of debris that has been left by Comet Swift-Tuttle as it orbits around the Sun which gives rise to one of natures most amazing spectacles, the Perseid meteor shower.
There are about 30 different meteor showers each year where the Earth passes through the debris left by other comets and they happen at broadly the same time every year. If you watch the meteors carefully during any particular shower, you may notice that they all seem to come from one point in the sky, we call this the radiant. They don't actually come from one point in space, its a visual effect arising from something we call perspective. You can see a similar effect if you stand on a bridge over a motorway, all the parallel lanes seem to come from one point on the horizon. The location of the radiant determines the name of the shower, for example the radiant for the Perseid shower sits in the constellation of Perseus.
During the shower, you can expect to see a number of fast moving lights zipping, unannounced across the sky, all seeming to come from Perseus. These lights are produced as tiny pieces of rock slam into our atmosphere at speeds in excess of 200,000 km per hour. On hitting our atmosphere the gasses in front of the rock get compressed to such a degree that they give off the characteristic flash of light. Typically, most of the pieces of rock (meteoroids) will burn up high in the atmosphere and when they do we call them meteors, if they are big enough to land then they are called meteorites.
This year then, in the early hours of 13th August, we will be treated to the peak in activity of the Perseids although it is possible to see meteors from this shower from now until the end of the month. Unfortunately the Full Moon will be present overnight on 12/13 August which means its bright light will block the fainter ones from our view. The best thing to do is get outside, away from bright street lights anytime before dawn between now and then and you should see plenty. Its best to look for them in the early hours as you are then on the front face of the Earth as it moves through space. Its a bit like all the flies you find stuck to your car windscreen but hardly any on the back window. Wrap up warm and set up a comfortable chair outside, lay back and watch. If you are lucky and you do see some, don't forget to make a wish.
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