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Posted at 09:42 AM ET, 10/21/2011

Orionids meteor shower peaks tonight

Fireball photographed during 2009 Orionids. ( NASA )
Skies early tomorrow morning (Saturday) before twilight should be clear and starry along the East Coast and across large parts of the country, but showers are a virtual certainty. Still, early rises risers venturing outdoors can leave the umbrella behind. The showers of which I speak will be bright streaks in the sky associated with the peak of the Orionids meteor shower centered on the morning of October 22.

The Orionids are one of the major shooting star displays each year. The name derives from the fact that meteor streaks appear to radiate from the just above the head of constellation Orion, the “Hunter” and not far (visually speaking) from its right shoulder marked by the bright red star, Betelgeuse.

Brilliant multiple meteor streaks that can all be connected to a single point in the sky just above the belt of Orion, called the “radiant.” ( NASA )
The Orionids are associated with debris from Halley’s Comet. Interestingly, the small particles (meteoroids) being ejected from Halley’s Comet now are currently much too distant to be the source of the Orionids. Rather, the meteor streaks reflect the intersection of particle “filaments” drawn to Earth’s orbit by the gravitational attraction of Jupiter. This is a very slow process such that the Orionids for this and many more years reflect particles ejected from Halley’s Comet at least two thousand years ago.

So far this has not been an especially great year for meteor showers. Typically the most prominent display of shooting stars is the Perseids in August. While several prominent streaks and a couple fireball s were observed last August, the Perseids were largely obscured by the light of a full moon. What might have been a spectacular meteor shower earlier this month, the Draconids , was not to be since the peak occurred during daylight hours over North America.

During the Orionids peak tonight, a waning crescent moon will rise into the eastern sky about 2:20 AM (Saturday). The 25% or so illuminated portion if the Moon’s disk might interfere somewhat with the Orionids, but not come close to overpowering the potential for a great show – providing you can find a nearby viewing location removed from the majority of light pollution from cities, shopping centers, etc. (and, of course, clear skies).

Via NASA: A map of the morning sky on Saturday, Oct. 22nd at 5:30 a.m. local time, viewed facing southeast ( NASA )
The maximum of the Orionids are likely between 3:00 AM and just before local sunrise (7:24 a.m. in the D.C. metro region). During this period the constellation Orion will be just about due south about halfway up the southern horizon. Meteoroids will streak and be visible in all directions away from the location in Orion they appear to radiate from, but best seen looking at the darkest portion of the sky, i.e., away from the moon and beginning hints of twilight near dawn.

On average watchers should expect to see between 15 and 20 yellow and green fast moving meteoroid streaks across the sky per hour. However, in the past few years Orionids have been especially strong and bright and accompanied by breathtaking fireballs that create persistent visible dust trails at high levels of the atmosphere. There is no way to know if this trend will continue through this year’s Orionids.

As great as in might be to “sleep in” on Saturday morning, rising early for this (or any other prominent meteor shower) is well worth the opportunity to see a natural wonder of the near space environment in which we all reside.

Please feel free to send in meteor sightings and your reactions to the experience. Submit photographs you take to our Night Sky gallery here.

By  |  09:42 AM ET, 10/21/2011

Categories:  Astronomy, Space, Latest

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