60 Minutes With The Orionids

Orionid meteors stream from a point in the sky just above the bright, red supergiant star Betelgeuse in Orion. Typically 15 meteors are visible per hour at maximum which occurs on the mornings of Oct. 21 and 22. Stellarium

The Orionids, a minor but always reliable meteor shower, peaks this coming weekend. Under a dark sky you can up to 15 meteors an hour and sometimes more. Because Orion doesn’t really crest the horizon until midnight, the best viewing times begin a couple hours before dawn. This year, when the constellation culminates in the southern sky. That happens around 5 a.m. local time or about an hour before the start of morning twilight.

You may have already heard that the waxing gibbous moon will brighten the sky and pose a problem for the Orionids. Moonlight and meteors never mix well, since a bright moon washes out the fainter ones, and there are always more faint flashes than bright ones.

An Orionid meteor slashes across the top of the frame directly above the constellation Orion during the 2014 shower. Details: 24mm lens, f/2.8, 30-seconds at ISO 1600. Bob King

But there’s a way around this. From many locations the moon sets between a hour-and-a-half to an hour before morning twilight begins. That’s also the time when Orion’s highest and meteors numbers peak. So … with a little planning there’s just enough time – and hour give or take – to sample the shower in a dark sky at the best possible time without lunar influence.

You can go out either early Sunday morning Oct. 21 or Monday the 22nd. Click here to find the moonset time for your location, then plan to be up and out a little before that. Orionids are swift, traveling at 148,000 mph (66 km/sec), and appear to radiate from the upraised club of Orion above the star Betelgeuse. You can look anywhere in the sky, so the direction you face doesn’t particularly matter, but I’m fond of south-southeast. For aesthetic reasons I like to keep the radiant constellation in view. And the Orionids have the best constellation of any shower hands down!

Orionids hail from Halley’s Comet. When Earth encounters the inbound leg of the comet’s orbit, we plow through the comet’s dust trail. Motes, particles, and tiny pebbles strike the atmosphere at high speed, flare, and create a shower of meteors. Perturbations by planets and the Sun have caused the particles to spread out into a ribbon centered on Halley’s orbit. Halley’s position is shown at perihelion in 1986 and in 2017, near the outer end of its orbit. Not to scale. Bob King

A reclining chair is the perfect piece of equipment for watching the shower along with a blanket you can snuggle under to stay warm. Now for the best part: Orionids aren’t just crumbs from any old comet. They’re fragments of the most famous one of all — Halley’s!  Some of you remember Halley from 1986. If you missed it you’ll have another chance when it returns in the summer of 2061. In the meantime, you can watch pieces left by the comet in its orbit disintegrate as zippy meteors as they slam into our atmosphere this weekend.

Clear skies!

2 Responses

  1. Kurt Moeller

    Dear Bob King; Thanks for the heads up on the Orionids. I’ll catch them as soon as the weather clears up. By the way, have you seen comet Wirtanen? is it really 9.8 already?

    1. astrobob

      You’re welcome, Kurt. I hope you have clear skies. I have seen Comet Wirtanen — last week. It was very low in the constellation Fornax and quite faint in my 15-inch scope. Part of the reason for that was altitude, part because the comet is large and very diffuse. I estimated mag. 10.5. When you mentally “crunch” down the comet’s size to compare it to a star of known magnitude, big, diffuse objects can sound remarkably bright. Visually, it’s a somewhat different story.

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