Orbit.

The Perseid Meteor Shower: Some further reading.

Have you ever wondered why the Perseid meteor showers occur so regularly and predictably? Whether this is something to do with their orbit coinciding with the Earth’s annually? Whether they orbit the Sun on a year cycle? Whether they’re in the same plane as Earth’s orbit and the other planets? Whether any 3D diagrams exist? Whether the Perseids are decreasing in number each year? Whether they come from the constellation of Perseus? Whether the tracks of all the meteors are the same?

Well, funnily enough, you’re not alone! My Uncle Andrew wondered all of these things at once, and contacted drainbamms.wordpress.com seeking further clarification.

I shall now attempt to answer all of his questions.

The particles associated with the annual Perseid meteor shower come from a comet called Swift Tuttle, which was discovered independently by Lewis Swift and Horace Tuttle on July 16th and July 19th 1862 respectively.

Yes, the comet does orbit the sun, but each orbit takes around 133 years, 11 times the length of Jupiter’s orbit. Swift Tuttle does not orbit on the same plane as the planets, but cuts across Earth’s orbit at an angle.

Image

The Perseids aren’t decreasing in number each year, as Swift Tuttle is still orbiting the sun and leaving a trail of dust particles behind it. Most of the dust in the cloud at the moment is thought to be around 1000 years old, although there is a newer stream of particles which was pulled from the comet in 1865 (presumably as it passed the sun? I can’t find clarification on this).

The meteor shower associated with Swift Tuttle is called the Perseid shower because to an observer in the northern hemisphere the meteors appear to radiate from a point in the sky closest to the constellation of Perseus. However, having observed the shower each year for a few years, I find the diagrams too simplistic, and in reality you’ll see the meteors all over the sky and won’t really be able to tell where they’re radiating from.

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And finally, an amazing fact of the day: The dust particles entering the atmosphere during this meteor shower are hurtling along at 58km/s.

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