The summer’s best sky show is happening this weekend: the famous Perseid meteors. This year, conditions couldn’t be better. There’s a New Moon this weekend, and skies will be ideally black. The shower peaks on two nights, Saturday and again Sunday night – with some experts thinking that Sunday could be the optimum time. All we need are mostly clear skies and, to be perfect, a night when the air is dry and not too hazy and humid.
Shooting stars were once regarded as strictly atmospheric phenomena, which is why we still call weather experts “meteorologists.” But meteors are swarms of comet debris, each the size of an appleseed, orbiting the Sun in the same path as the original comet. In this case the comet is Swift-Tuttle, a big monster discovered during the Civil War, which orbits the Sun backwards.
We meet that comet every 133 years, and sometimes it’s an unnervingly close encounter. Computer simulations show that we’re safe for the next half-millennium. But if it ever hits us, it will make the K-T (now called K-Pg) dinosaur extinction seem Little League by comparison. Thanks to its large size and unusually fast speed, Comet Swift-Tuttle is the most hazardous object in the universe, so far as earthly life is concerned.
When Earth annually meets the backwards swarm of material that sloughed off the comet, the collisions happen at the same unusual speed of 37 miles per second. And, although meteors can appear anywhere in the sky, they all seem to emanate from a single spot: a common point called the radiant, which in this case lies within the constellation of Perseus.
Perseus rises around 10:30 p.m. So before then, the meteors all streak upward from the radiant point, which is then below the northeast horizon. But after 11 p.m. or midnight, they streak away from the northeast heading right, left or upward, and hence there’s more of them. After 2 a.m., Perseus is so high up that you can see shooting stars going up, left, downward or rightward, so that’s when you see the most.
Once in a while you’ll see one that goes in a different direction from all the Perseids. Such sporadics make up about ten percent of each hour’s meteor inventory. They’re strays, slamming into our atmosphere from arbitrary directions.
If all this sounds intriguing (and of course it does!), just turn out all the house lights and lie on a blanket or lawn chair facing a large opening to the sky. As I’ve done since the 1980s, I’ll be holding the annual Night of the Shooting Stars program at the Mohonk Mountain House at a dark, secluded soccer field where staff members bring towels to lie on. I’d love to see you there. But, to be honest, your own back lawn will work just fine.
This should be our best meteor shower since 2003 – if the weather cooperates.
Want to know more? To read Bob’s previous columns, visit our Almanac Weekly website at HudsonValleyOne.com. Check out Bob‘s new podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.