Sky Talk October 2007: The Orionid Meteor Shower

The annual Orionid Meteor Shower will provide another fine display of celestial fireworks for skywatchers during the early morning hours of October 21st. The window of opportunity for having a dark sky in which to see these “shooting stars” occurs soon after the 9-day-old Moon goes down around 1:30 a.m. EDT and before the Sun comes up. So plan to head to bed early the night before and set your alarm accordingly; losing some sleep to get up in the wee hours for a meteor watch will definitely be well worth it!

Given clear skies on the morning of October 21st, observers will be treated to one of the year’s most reliable displays of shooting stars — the Orionids. Peak activity occurs around 5 a.m. EDT, with as many as 25 meteors an hour being visible under good conditions.

While not one of the richer showers, it’s radiant (the point from which the meteors appear to “shoot”) is located in a glorious part of the heavens — that of magnificent Orion! The actual point lies between Betelgeuse in the Hunter’s shoulder and (this year) nearby Mars, with both sentries glowing a brilliant ruddy-orange in hue.

Observing shooting stars is basically a naked-eye activity in order to canvass as large an area of sky as possible. Meteors are typically best-seen some distance from the radiant itself, so facing in its direction and looking overhead gives the best results. (And reclining on a lawn chair certainly helps while doing so!) However, use of your binoculars from Edmund Scientific (specifically, the Celestron SkyMaster: #30311-02) is also encouraged for following the fascinating drifting “smoke” trails (or trains) left by many of the brighter meteors. The Orionids are known for being very swift and for leaving trains behind them, so having a quick reaction-time is a real asset here!

At moonset on the 21st, Orion will already be high in the southeast and meteoric activity will increase throughout the early morning as the radiant continues to rise higher in the sky. But there’s also another more significant factor at play here. During the evening hours we’re on the side of the Earth “facing away” from the direction the meteors are coming and they have to “catch up” to us. But after midnight we’re turned into the direction of the radiant, causing the meteors to slam into the atmosphere at much higher speeds — resulting in many more of them being seen, and those that are seen to generally be brighter and more spectacular. So observing the Orionids in the early hours of the morning is doubly justified this year, with waiting for the Moon to set and for peak activity to occur before the Sun comes up.

As a point of interest, meteor showers result from our “Spaceship Earth” circling the Sun and running into streams of debris each year left behind by various comets in their orbits. In the case of the Orionids, their source is perhaps the most famous of all such objects — none other than Halley’s Comet itself!

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of five books on stargazing.

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