Amazing Places

Here's Why the Perseid Meteor Shower Shows Up Once a Year

For a few weeks over late summer in the Northern Hemisphere, the night sky begins to light up with tiny streaks of light. These are meteors from the Perseid meteor shower, which burn brightly as they hurtle through our atmosphere at red-hot speeds. The Perseids reappear on cue once a year, but it's not them who are visiting us — it's our planet's own journey through the solar system that makes this light show so punctual.

Perseid Meteor Shower Time Lapse from 2016

Comet Me, Bro

The Perseid Meteor Shower is named after the constellation Perseus since that's where the meteors appear to originate. But it's not. A constellation, for one thing, isn't actually a single entity that could produce a meteor shower. Constellations are made up of many stars that only look like they're close to each other — one star in Perseus is about 100 light years from us, while another is 750 light years away, for example. Instead, the Perseids are created by the dust and debris left over from Comet Swift-Tuttle. That's right: That beautiful light show is produced by what's essentially a comet's exhaust.

Perseid meteor shower as seen from Bracebridge, Ontario in August of 2013.

Comet Swift-Tuttle is the largest known object to repeatedly pass by Earth, which it does once every 133 years. The last time it passed by the Earth was in 1992, and there are historical records that suggest ancient astronomers saw the same comet as far back as 188 A.D. But the comet doesn't need to be nearby to put on a show. We pass through its debris trail every year in our annual path around the sun. As the tiny pieces of rock and dust leave the vacuum of space and hit the friction of our atmosphere, they travel at 37 miles (59 kilometers) per second: an incredible speed that heats up the surrounding air and turns it red-hot. Most of the meteors burn up before hitting the ground, but some make it through to become meteorites. (Contrary to popular belief, meteorites aren't hot when they land.)

How You Can Catch the Show

Time-lapse image of Perseid meteors lighting up the sky in August 2009.

So how can you catch a glimpse of this natural light show when it comes back around? In 2018, astronomers predict that the Northern Hemisphere will see the greatest number of meteors on the nights of August 11, 12, and 13. 2018 is in store to be quite a show, since this year's meteor shower coincides with the new moon, so the meteors don't have to compete with moonlight for our attention.

Written by Ashley Hamer August 1, 2018