Teardrops from the Sky Gods

I bet you I could forecast what my astronomy associates will be doing on the night of August 12-13 (Thursday-Friday) this year. No, I’m not a psychic! That date is the night of the annual Perseid meteor shower, and with practically ideal observing circumstances predicted, there are going to be a few sleepy amateur astronomers on Friday the 13th. Hopefully the weather will cooperate so stargazers and casual enthusiasts can enjoy a bountiful display of celestial teardrops.

If you are a regular reader of this column you are more than likely familiar with the general characteristics of meteor showers. A long-time reader may even know the specifics about the Perseids. If so, and you don’t need a refresher, you can skim through a few paragraphs until you come across the observing circumstances for this year.

During a meteor shower an observer sees particles, many no larger than a thumbnail, plunge into our atmosphere at many miles per second and disintegrate. The August Perseids, which occur around the same time each year, are the remnants of Comet 109P/Swift-Tuttle that were stripped off the comet’s surface and deposited in “streams” throughout its orbit about the Sun. When the Earth passes through this stream we experience a display of shooting stars.

The Perseids are a fairly consistent display, though some years ago when clear skies provided us a good view, the number of meteors fell far short of predictions. In 2010 we are expecting to observe the normal peak rate of about 60 meteors per hour from a dark sky. That number may even be higher if one can observe from a really dark sky site along the Rhode Island south coast. Then perhaps 80 or more meteors per hour will be seen.

Wherever you decide to observe from, maximize your chances of observing as many meteors as possible by selecting a location well away from light pollution and get comfortable on a lounge chair or in a sleeping bag. A waxing crescent Moon will set around 9:00 pm on the 12th, so it won’t diminish the number of meteors that can be seen. As usual though, you will most likely be plagued by mosquitoes, so be sure to protect yourself to stay off their banquet menu.

I would suggest you begin your observing program around midnight. Between then and dawn is when the peak activity should occur. For fun, keep a written or mental count of meteors per hour. You should note an increase as the morning progresses.

The Perseids are so named because they appear to radiate from an area of sky, called the radiant point, in the constellation Perseus. Perseus is well up in the northeast sky after midnight. If you can see a pattern of stars that looks like a sideways “M” or “W” (that’s Cassiopeia), Perseus is below it so you’re looking in the correct direction. You know you’ve seen a Perseid if you can trace the path of a meteor back to the radiant point. Also, the Perseids are usually green, red or orange in color and blaze across the heavens at 134,222 miles per hour. And some members of this shower are bright and often produce exploding fireballs.

If the weather does not cooperate or you are unable to observe on peak night, try your luck on the nights before and after. You won’t see 60 meteors per hour, but you may catch a couple of dozen or so. The best time to observe will still be between midnight and dawn’s early light.

Meteor observing prospects don’t get any better than what is forecast for the 2010 Perseids. Furthermore, I do have another prediction. There are going to be many sad and frustrated stargazers on August 13 should the teardrops of the gods fall from the clouds (rain) and not the celestial heavens (meteors).

Don’t forget that Seagrave Memorial Observatory (http:/www.theskyscrapers.org) in North Scituate is open for public viewing every clear Saturday night. Our summer hours are from 9:00 – 11:00 pm, weather permitting. If in doubt, check our web site for weather closures.

The renovations at Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence are continuing, and the observatory remains closed at this time. Please check the web site for updates before visiting.

Good luck and keep your eyes to the skies.