Why are meteor showers like the Perseids so common? Turns out, space isn’t as empty as you might think. It’s littered with debris that forms those spectacular meteor shower we look forward to each year. Following is a transcript of the video.
Solar eclipses are rare and you can never predict when an aurora will illuminate the sky. But there's one cosmic light show we can always count on. Meteor showers. They happen around the same time each year and have been doing so for centuries. But despite their brilliance and beauty it doesn't take much to make a meteor shower. You just need three ingredients, the sun, Earth and a comet.
Comets have been around since the dawn of our solar system over four-and-a-half billion years ago. They formed out of the same disc of gas and dust that created earth and the other seven planets. And like the other planets they too orbit the sun but that's where the similarities end. Most planets orbit the sun on fairly circular orbits whereas comets take a more elliptical path through our solar system. Check out Halley's Comet for example. Right now it's beyond the orbit of the furthest planet Neptune. But over the next 50 years it will travel about three billion miles toward the inner reaches of our solar system. Eventually flying past Earth in the year 2061.
And it's encounters like this that make meteor showers possible. Because as a comet approaches the inner solar system, the sun's radiation heats up ice under the surface and as that ice turns to a vapor it generates powerful outbursts of gas and dust, sometimes ejecting hundreds of tons of material into space per second. The result is a brilliant stream of debris called the comet tail or coma, which can stretch hundreds to thousands of miles across. In fact, space is littered with comet tail debris that our planet passes through each year. And when that happens, the debris strikes our atmosphere at over 100,000 miles an hour, incinerating the four-and-a-half billion year old fragments in seconds. This produces brilliant flashes of light that we call a meteor shower.
Now some meteor showers are more spectacular than others, giving us anywhere from a few to over a hundred meteors an hour. And even the same meteor shower can vary from year to year. It all depends on how much debris we scoop up as we pass through the tail. Regardless, comet tails tend to follow the same path as the comet itself, which means they pass through the same spot along Earth's orbit. That's why we get the same meteor showers around the same time each year. At the end of October for example, we pass through the tale of Halley's Comet which gives us the Orionids meteor shower. And every August, we pass through comet Swift-Tuttle's tail which we see as the Perseids meteor shower. But it's not just October and August, meteor showers occur year-round. So check your calendar to see when the next one will be coming to a sky near you.