Danger from the summer meteors

A shooting star seen the Perseid Meteor Shower over White Island Pond in Wareham/Plymouth, Massachusetts. (Flickr | MK Feeney)

The year’s best meteor shower is now under way. It starts with just a few extra shooting stars per hour. But when we reach the nights of August 11 and 12, we will see a meteor every two minutes or so, especially if we’re away from the lights of town.

But there’s a secret sinister untold story behind these lovely shooting stars. It involves their origins.

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Meteors are tiny specks of debris that have fallen off a comet. Most are no larger than apple seeds. These particular meteors have been observed for over 2000 years, and were chronicled by ancient Chinese sky watchers. They all seem to streak away from the constellation of Perseus, which is why they are called the Perseids. But the orbiting path of each of these tiny bits of dirty ice shows that they share an orbit with the comet Swift Tuttle.

That comet came close to earth during the Civil War, when it was discovered the same week in July 1862 by two famous astronomers, Horace Tuttle and Lewis Swift. 

The comet has a 133-year orbital period around the sun, locked by Jupiter’s gravity so that it is synchronized with that giant world, and makes one orbit in exactly the same time period in which Jupiter circles the sun eleven times. Very cool. This made it next approach us in the mid-1990s. But that was an unusually poor and distant apparition, and the comet couldn’t even be seen with the naked eye.

But what makes us really sit up and pay attention is that some comet experts have called it the most hazardous object to human life in the entire universe. Wow.

That’s because comet Swift Tuttle is big and has the potential to approach us so closely that sooner or later it may collide with us, Worst of all, it goes around the sun in the opposite direction from the way we do. So if and when it does hit us, it will be a head-on impact. 

The speed is actually obvious each year when we watch the summer Perseid meteors. They are very nearly as fast as meteors can possibly be. They streak into our atmosphere at 37 miles per second, which is about 80 times faster than a high-velocity rifle bullet. That’s the same speed the comet would hit us. It would be more devastating than the extinction event 66 million years ago that destroyed the dinosaurs and allowed for the ascent of all the beloved mammals that now populate our world, like humans and rats.

There’s much to think about as we observe these fine summer shooting stars.