Jimmy Westlake: July's mysterious meteors



Jimmy Westlake/Courtesy

Meteors, or "shooting stars," occur when tiny bits of space dust burn up in Earth's atmosphere about 60 miles high. This month's Delta Aquarid meteor shower will offer 1 to 2 dozen meteors each hour, at its peak July 27.

Jimmy Westlake

Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.

Find more columns by Westlake here.

Do you enjoy watching meteors shoot across the sky? This month's annual Delta Aquarid meteor shower promises to put on its best performance in years.

Although not generally considered to be one of the richest annual meteor showers, the Delta Aquarid shower can produce from a couple of dozen meteors each hour at its peak, which this year falls on the morning of July 27.

Meteor showers are named for the constellation from which they seem to radiate, so we have, for example, the August Perseids, which radiate from the constellation of Perseus, the December Geminids, which radiate from the constellation Gemini, and this month's Delta Aquarids, which seem to spring from near the star Delta in the constellation Aquarius.

Our annual meteor showers are produced when the Earth plows through the path of an old comet and collides with leftover dust particles in the comet's wake. The parent comets for most of our major annual meteor showers have been well established. For example, the May Aquarids and the October Orionids are produced when Earth crosses the orbit of Halley's comet, twice each year. July's Delta Aquarid shower is unique in that it is the only strong shower whose parent comet is unknown. Either the parent comet was pulled into a different orbit long ago after a close pass by one of the outer planets, or it met with some catastrophic end. The primary suspect is periodic comet 96P/Machholz 2, which crumbled into pieces as astronomers watched it round the Sun in 1994, but this conclusion is far from certain. For the present time, the source of the July Delta Aquarid meteors remains a mystery.

To watch the Delta Aquarid meteor shower, you'll need to set your alarm for about 3 a.m. Sunday morning July 27, or else (like me) just stay up all night long. The constellation of Aquarius doesn't rise until about 11 p.m. Saturday night, so, don't expect to see any Delta Aquarids before then. Aquarius is highest in the southern sky about 4 a.m. This will be the best time to watch. The meteors will seem to dart in every direction, but their paths will all start from near the star Delta Aquarii, just above the bright star Fomalhaut. You might see about one or two shower meteors every 5 minutes, on average. It's more of a sprinkle than a shower, really. Consider the Delta Aquarids just a warm-up for the August Perseid meteor shower, which can produce more than one meteor per minute!

As an extra bonus for late-night meteor watchers, the fat waning crescent moon will rise after midnight right beside the beautiful Pleiades star cluster, also known as the Seven Sisters. Use your binoculars to enhance the view of the star cluster twinkling in the moonlight.

Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day" Web site, Spaceweather.com, Space.com, Discover.com, MSNBC.com, NationalGeographic.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines. His "Celestial News" article appears weekly in the Steamboat Pilot & Today. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's Web site at www.jwestlake.com.


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