Every year in late October, Earth plows into a “snow flurry” of dust and small fragments shed by Halley’s Comet during its many passages of the sun. The last time Halley dropped by our vicinity was in 1986, and it’s expected again in 2061. Every time the comet draws near the sun, solar heating boils away ice and dust from Halley’s icy surface and interior. Pushed around by the planets and sun, the comet’s debris trail spreads widely around its orbit.
When Earth passes through, the motes and pebbles strike our upper atmosphere at over 148,000 miles an hour; as they incinerate into fine dust, we see flashes of light, what many of us call shooting stars but more formally known as meteors. Meteor showers are named for the constellation from which they appear to originate. So we have the August Perseids (from Perseus), December Geminids (Gemini) and the October Orionids (Orion).
On a dark, moonless night, we would expect to see about 20 meteors stream from a “radiant point” high in Orion’s Club. During any shower, meteors can appear anywhere in the sky, but all those comet crumbles trace their paths backwards to the radiant. If it comes from the direction of Orion, it’s an Orionid.
This year’s shower has some unwelcome competition from the last quarter moon, located not far from the radiant in Orion and Gemini over the next few nights. Moonlight will brighten the sky and cut into the number of meteors we’d normally see. While not as overpowering as say the full moon, there’s enough light from half a moon to cut the number of Orionids in half.
The shower will be active through about Tuesday morning October 25, but the peak of activity occurs tomorrow morning (Oct. 20) and especially Friday morning Oct. 21. For the best view, plan to be out in the two hours before the start of dawn or from about 3:30-5:30 a.m. That’s when Orion stands high in the southern sky. Dress warmly and flop out under a warm blanket or sleeping bag facing toward the east or southwest. Although it wants you to look, avoid staring at the bright moon, so you can preserve your night vision and see as many meteors as possible. Orionids move swiftly and make for exciting viewing.
Meteor shower watching is easy and fun. I like to keep an informal count to compare year to year. Not only will see at least a few shooting stars, you’ll also get to enjoy the winter constellations overhead. Happy Halley hunting!