By: Natalie Shoemaker, Advancement Coordinator

The spectacular Perseid meteor shower may have put you in a mind to ponder the very nature of a meteor shower. Truly, what are these shooting stars and what causes them? Good question.

When you see a bright light rocket across the sky, you are witnessing the fiery demise of a tiny bit of comet dust. This piece of dust (usually no larger than a grain of sand) enters Earth’s atmosphere at a whopping 158,000 miles per hour. It’s there, then gone.

But there’s quite a bit of history to this cosmic dust, it’s actually remnants of a comet that passed through our solar system hundreds, maybe thousands, of years ago. Not to mention traveled billions of miles.

geminid comet dust
Photo Credit: NASA/JPL

When the comet gets close to the sun, it begins to melt, shedding off pieces of gas dust and ice. This creates a cloud of remnants. It’s when Earth passes through these dust clouds that we get meteor showers.

The comet dust that skywatchers will see in the upcoming Perseid meteor shower actually came from Comet Swift-Tuttle, a celestial body measuring 16 miles across, which is roughly the same size of the asteroid that killed the dinosaurs. And it’s one of the many reasons why NASA has been keeping a close eye on it.

Comet Swift-Tuttle makes a pass by Earth every 133 years. But interest in Swift-Tuttle’s goes beyond the entertainment value it provides to us each August.

On its next visit into our solar system, Swift-Tuttle is supposed to pass 15 million miles from Earth. However, some scientists believe sometime in the year 3044, this comet may pass within a mere million miles from Earth. This is what’s known as a true near miss in the cosmos.

Even before then, another asteroid called Apophis will have a 1 in 250,000 chance of hitting Earth in April 2036. But not to worry, Bill Nye says we have a lot more to defend ourselves against asteroids than dinosaurs did.

Like science? Let us know what other kinds of questions you have. Send them over to nshoemaker@gsnypenn.org.

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