Monday, 14 August 2017

The Perseid Meteor Shower - 2017

This week I’m going to be talking about something a little different from my usual topic.
As you might be aware; usually I’ll write about things to do with the history of British space exploration or research.

If any of you looked up into the sky this weekend, particularly in the early hours of Sunday morning, you would have been greeted with the incredible sight of multiple shooting stars. Sometimes as often as every few minutes.

Perseids - 2017 by Rachel Sykes
This wonderful image is made by combining 2 separate images and was made by Rachel Sykes of Edmonton, Canada.

The Perseid Meteor shower happens at around the same time every year and gives us an incredible chance to see numerous meteors simply be relaxing in our own back yards. Even this year, with a very bright moon, I was able to sit in the garden, stare up and see three or four within 10 minutes and I live near the centre of a very bright city!

But where do these meteors come from?
And why do they happen at the same time year in, year out?

Meteors are essentially the dusty and particulate remains of comets or asteroids. As these objects orbit our sun they leave this trail behind them as we leave footprints in snow.
In turn, as the Earth orbits the Sun, once a year it passes through these clouds, allowing the dust and particles to burn through our atmosphere and treating us to meteor showers. The bright streaks tearing across the sky are often caused by particles no larger than a single grain of sand.

In particular, the meteor shower that we witness every August is caused by the Earth passing through the dust trail of of the Swift-Tuttle comet (109P).

Swift-Tuttle is still in orbit around our sun and takes 133 years to complete its orbit. It was discovered in 1862 by Lewis Swift and Horace Tuttle. In comet terms, it’s big! Very big! It’s nucleus is 16 miles across which is nearly twice the size of the comet that some scientists believe to have lep to the extinction of the dinosaurs.

Comet Swift-Tuttle
A giant ball of dirty ice, Swift Tuttle last passed by the inner solar system in 1992 and the closest it gets to the Sun is 0.96 AU. (1 AU, or Astronomical Unit, is the approximate average distance between the Sun and the Earth) and the next time it’s due to pass closely with Earth is in 2126 causing some people to speculate that it will collide with the Earth. This, it must be said, is highly unlikely!

Orbit of Comet Swift-Tuttle

The only thing I haven’t mentioned is why the meteor shower we observe is called the Perseid Shower. This one is nice and easy to answer.

If you look up towards the constellation of Perseus during the peak of the shower, the ‘shooting stars’ will look as if they are coming from within that constellation. Perseid comes from the Greek ‘Perseidai’ which means Sons of Perseus.

I hope you found this short post interesting and I will be back to rockets and satellites very soon.

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