Friday, August 12, 2011

Perseid Meteor Shower 2011


Go outside before dawn, and if the Perseid meteor shower of 2011 is good to you, you will be able to see the sky falling.
Every year at this time, the Earth passes through the orbit of a comet called Swift-Tuttle, and the result is a meteor shower -- shooting stars, up to 50 or 60 per hour -- streaking across the night sky as debris from the comet enters the earth's atmosphere and burns up.
Even though the comet is far away now, in an elliptical orbit that brings it close to the sun just once every 133 years, rock and ice from it have spread out in a ring all along its path. The comet itself will probably be pretty good to see if you can hang on until July 2126, but in the meantime, like clockwork, it gives us an annual meteor shower in mid-August.
Sadly, this is not the best year to see the Perseid. A full moon will brighten the sky on Friday night and Saturday morning, just as the shower peaks. But don't give up.
"The best time to look is during the hours before dawn especially on Saturday morning, August 13th," writes Tony Phillips, an astronomer who manages the Science News page at NASA's website. "The full Moon will be relatively low, and the meteor rate should be peaking at that time."
There's an added bonus if you're willing to give up some sleep. The International Space Station -- visible as a bright star moving steadily across the sky -- will pass over North America several times each morning this week, and can be seen at different times in almost every part of the U.S. For specific times and directions where you live, take a look atNASA's Human Spaceflight site, which now includes a "SkyWatch 2.0" applet.
Be alert; most meteors streak by in a second or less, sometimes in clusters. Most of the shooting stars are created by small cometary fragments, some as small as grains of sand, completely vaporized as they plunge into our protective blanket of air.
The best way to see them is to find a nice, dark place with no street lights and as few trees as possible, and look up. You may be happiest in a lawn chair or a sleeping bag. The streaks could appear anywhere in the sky, though they'll all appear to come from the constellation Perseus, in the northeastern sky, after midnight.
You're best off if you park yourself so that the moon, setting in the west, is behind you, and you let your eyes get used to the darkness. It may help if the moon is blocked by trees or a building, but then part of the sky will be blocked too.
In general, there are more shooting stars in the morning hours because that's the side of the Earth that faces forward as we orbit the Sun, so it's less shielded. While the shower actually peaks early Saturday morning, Perseid meteors are often spotted several nights before and after.
At their best, the Perseids usually let you see one or two shooting stars a minute -- but only if you're far from cities, have clear skies, and happen to be looking in the right direction. (Go to our weather page for conditions near you.) Astronomers will tell you that meteor showers are best if you regard them as something to be savored, rather than awed by.
"If you want fireworks, go find a video of fireworks on YouTube. This isn't like that. This is about being part of nature and the wider cosmos," said Alan MacRobert, a senior editor of Sky & Telescope magazine in an e-mail to ABC News.
"Most people never look up. They go about their busy little lives wrapped up in their busy little concerns here on the ground like ants in an anthill," he said. "Amateur astronomers -- and nature people in general -- are people who sometimes stop to look up, and to take the time to find out about what they see."
If you're lucky, it will be a nice show. And you'll have the satisfaction of knowing that Chicken Little was half-right: The sky will indeed be falling...harmlessly.

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