August 6, 2013
Waxing Moon Won’t Affect Perseid Meteor Shower This Year
Lawrence LeBlond for redOrbit.com - Your Universe Online
Late last month, NASA's Bill Cooke explained "one meteor shower produces more fireballs than any other." Now, two more sources are coming on board and alerting that this year's Perseid meteor shower will be one of the best displays in recent years.
According to StarDate magazine, this year's Perseid meteor shower will peak on the nights of August 11 and 12, with prime viewing times beginning after midnight on both nights. The meteor shower is expected to be at its peak during daylight hours as seen from US soil, so the shower may not be as impressive as in some years with nighttime peaks. Still, under dark skies away from city lights, sky watchers may see as many as a few dozen meteors per hour, most notably in the pre-dawn hours of August 12.
Sky & Telescope has also weighed in on the subject and maintained this year's meteor shower display could be more impressive due to the fact it is occurring with almost no moon. A thick waxing crescent moon sets in mid-evening, so it will not interfere with prime viewing times during this year's peak nights.
Anyone stepping outside after 9 pm EDT on both August 11 and 12 may see some Perseids, but they do not begin picking up in intensity until after 11 pm, with most activity occurring in the early pre-dawn hours on August 12 and 13. This is when the shower's radiant point in northern Perseus climbs high in the northeastern sky, when the Earth turns to face the oncoming meteor stream directly. This should allow for quite a show, especially with no hindrance from the moon.
The predicted peak of 100 meteors per hour by the International Meteor Organization (IMO) may be just a bit overemphasized, but Sky & Telescope admits "surprises can always happen."
The Perseids get their name from the radiant point they appear to hail from in the sky: the Perseus constellation. However, like all meteors named after constellations (e.g. Leonids, Geminids), the Perseids actually hail from a comet debris field, in this case, the debris field comes from the passing of the comet Swift-Tuttle. Each year when the Earth passes through the debris field of this comet, it is pelted with particles that rain down through the atmosphere, creating fiery trails in the night sky for mere seconds as they burn up overhead.
The best way to view these fiery remnants is to go outside, away from city lights, and in an area that provides a wide-open view of the night sky -- an open field works best. Lie on a blanket on the ground or bring a reclining lawn chair and look up. In many areas around the US, it may be a good idea to have a thermos of hot chocolate or coffee and a warm blanket to stay warm; clear nights in August tend to bring chillier temperatures through most of the northern US, thanks to radiational cooling.
"Relax, be patient, and let your eyes adapt to the dark," says Robert Naeye, Sky & Telescope's editor in chief. "With a little luck you'll see a 'shooting star' every minute or so on average."
While Perseids appear to come from the Perseus constellation, viewers do not need to find the actual constellation in the night sky, which does rise over the northeastern sky as the night passes. The Perseids will actually appear anywhere and everywhere in the sky -- just look up. Most Perseids will appear as tiny, faint streaks of white light that leave short trails in the sky. Some lucky viewers may see brighter ones that seem to persist across the entire night sky, leaving a train of glowing smoke across the heavens. These fireballs are generally larger particles that take longer to burn up in the Earth's atmosphere.
Sky & Telescope suggests when you see a meteor, try tracking it backward to the point where you first saw it. If you trace it back to the constellation Perseus, then you just witnessed a Perseid. However, the Perseids are not the only meteor shower visible in the night sky this time of year. Occasionally an interloper may be visible streaking across the sky as well. Both the Delta Aquariid and Kappa Cygnid meteor showers persist during the Perseid season. However, these showers are generally weak and do not produce the same spectacular shows as do the Perseids. Still, a few random meteors may be viewed, which when traced back will appear to hail from a different area of the sky then the Perseids.
These "shooting stars," as they are often called, are not really stars at all. They are actually tiny, pea-sized bits of dusty debris shed by the comet Swift-Tuttle. Swift-Tuttle last passed earth in 1992, causing the yearly Perseids to become much more pronounced for several years; these annual events have since returned to normal, however. Swift-Tuttle will not make a return appearance in our neck of the woods again until 2122.
When these pea-sized fireballs come crashing down on Earth, they do so at speeds close to 37 miles per second, or more than 133,000 miles per hour. When they collide with the planet's atmosphere they create superheated plasma along their path. This incandescent gas, which includes vapor from the fiery particle, creates a momentary streak of light that we see in the sky, according to Sky & Telescope.
Bigger particles create even bigger flashes, called fireballs.
NASA's scientists have amassed a sizeable database of meteor shower events utilizing a vast network of meteor cameras distributed across the southern US. This database includes a wealth of bright meteors caught on camera since 2008. This ambitious project has proven to NASA the Perseids have shown the greatest display of flashes than any other annual shower to date.
For those who wish to learn more, StarDate magazine provides readers with a wealth of information on skywatching tips, news and features. The magazine also produces an annual Sky Almanac each January. The magazine is published bi-monthly by The University of Texas at Austin McDonald Observatory.
As well, Sky & Telescope offers helpful tips that should enhance your Perseid viewing this year.
Also, viewers are encouraged to make meteor counts and report their findings to the IMO or to the North American Meteor Network.
Image Below: The Perseid meteors appear to stream away from the shower's "radiant" point near the border of Perseus and Cassiopeia. This is the perspective point where they would all appear to be coming from if you could see them approaching in the far distance. In fact we see them only in the last second or two as they streak into Earth's upper atmosphere, and this can happen anywhere in your sky. Credit: Sky & Telescope