Bright Moon Dings Monday’s Orionid Meteor Shower

The Orionids are a reliable if minor meteor shower that returns every year in late October. Despite moonlight, keep watch for the occasional bright Orionid shooting from above the constellation Orion near the bright planet Jupiter on the mornings of Oct. 21 and 22. This map shows the sky facing south around 5-5:30 a.m local time.  Stellarium

Darn moon. We love its radiance but sometimes it just gets in the way. Count on it being there Monday morning Oct. 21 during the peak of the annual Orionid meteor shower. The shower is best seen in the wee hours before dawn when the radiant point, the spot in the sky from which the meteors will all appear to radiate, is high in the south above the upraised arm of Orion the Hunter.

Composite of many Orionids as recorded by Ohio amateur astronomer John Chumack

Normally we’d expect to see up to 20 very swift meteors per hour but moonlight will halve that number. Don’t let that stop you. The sun rises late, so you can squeeze in a little meteor watching between 5 and 6 before work.

Use the morning to dig out that old telescope and check in on Jupiter and the wonderful display of lunar craters along the moon’s terminator, the dividing line between day and night. I usually multi-task during meteor showers, poking the scope around from this to that while taking breaks for meteor-watching.

The Orionids are so-named because all the meteors appear to originate from northern Orion. But they’re also “Halleyids”, crumbs dropped by Halley’s Comet during its 76-year orbit of the sun.

Meteors appear to radiate from a point in the distance the same way snow striking your car windshield does when driving. Even though snowflakes and meteors are nearly parallel to each other, our eyes see them as converging in the distance. A similar illusion happens when looking down a set of train rails. Photo: Bob King

Each streak of light you see signals the incineration of a flake of Halley’s Comet, the parent comet of the Orionids. Every year in late October, Earth cuts across Halley’s orbit and bits of dust shed by the comet from previous passes near the sun burn up as they strike the upper atmosphere at speeds of 148,000 mph.

Few showers offer up faster meteors. Don’t bother pointing one out to an observing companion – it’ll be gone as soon as you open your mouth. Most tear across the sky in second or less.

We cross Halley’s orbital path twice a year, and each time we do, our planet slams into sand-sized bits of debris strewn by the comet during the many times it’s circled the sun. Our other encounter with Halley leftovers happens every around April 21 during the Delta Aquarid shower.

Watch for Orionids between about 2 a.m. and dawn. South or southeast is a good direction to face once you’re cozy under a big blanket to stay warm. The shower lasts a few days, so if the weather looks bad, try the mornings before and after Monday’s peak.

8 Responses

  1. Edward M. Boll

    I have been relying on Comets this Week for updates on the brightening trio. But the last observation they have recorded for us to see was Lovejoy on Oct. 4 at magnitude 10. I have not seen the 3 yet but wonder how they are doing at this present time.

  2. Edward M. Boll

    I did get the recent update. I think that Lovejoy should be an easy target for large binoculars in about a week. Thanks. Also, if the outburst of Linear X 1 continues for a while, I might be able to see that one too.

  3. caralex

    Bob, this article is on Yahoo today – what the moon would look like from a distance of only 400 kms – the height of the ISS.

    What intrigued me (apart from the fact that the video shows a completely calm earth – not a hint of the destruction and havoc that would be wreaked – but never mind petty details like that!), is the fact that day would turn to night in an instant. I was wondering, if the orbit were the same as it is now, tilted at 5 degrees to the plane of earth’s orbit, would every point on earth see this total eclipse every 90 minutes, or would there be parts of earth that would escape it?

    1. astrobob

      Really enjoyable article and video Carol, thanks for sharing it. Judging by the moon’s size (many degrees!) I would say that the 5 degree tilt wouldn’t be enough to prevent an eclipse from being seen everywhere every orbit.

      1. caralex

        Thanks, Bob. After posting, I watched the video again, and in the beginning of the animation, it shows the earth and moon in diagram form, with the moon casting its shadow on the earth. I don’t know if it’s to scale, though, so it’s hard to know how much of the earth would be covered by the shadow each time.

        1. astrobob

          Now I’m wondering about the simulation. If the moon were 1/10 of 1% of its distance from Earth, it would be 1000 times closer and 1000 times larger. 1000 x 1/2 degree (its current diameter) equals 500 degrees, which much more than covers the ENTIRE sky. The simulation then makes it look much too small. It would rise to cover the entire sky.

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