August 11, 2012
The Perseid Meteor Shower – Old Faithful Of The Skies
[ Watch the Video: ScienceCasts: 2012 Perseid Meteor Shower ]
April Flowers for redOrbit.com - Your Universe Online
Every year in August, the Perseid Meteor shower is visible to the naked eye and is a favorite for professional and amateur astronomers alike.
The Perseid shower has it all. It offers a consistently high rate of meteors, it produces more bright, visible meteors than any other shower, it happens in August when many people are on vacation, and it happens at a time when nighttime temperatures in the Northern Hemisphere are reasonable and the weather is good. What more could you ask for?
You could ask for the 2012 shower, because we have two added advantages. The moon will be in a waning crescent phase. That means on the night of the peak shower, the moon will be at about 25%, so it won't block viewing. The second advantage is that the shower peaks on a Saturday night, so most people can afford to stay up late or sleep in on Sunday morning.
This year, the shower peaks on the night of August 11/12. You can expect to see somewhere around eighty "shooting stars" per hour between midnight and dawn. Add in the fact that just before dawn, Jupiter and Venus will join in and this promises to be one of the best Perseid showers in memory.
According to NASA, people have been watching the Perseid shower for about 2000 years. Even better, the meteors we see this year were ejected from their comet approximately 1,000 years ago. They are made up of debris left in the wake of the Swift-Tuttle comet, which only passes Earth every 135 years. Swift-Tuttle leaves a long trail of meteoroids, which the Earth passes through every August. The meteoroids burn up when they hit Earth's atmosphere, giving us the showy shooting stars.
Horace Parnell Tuttle and Lewis Swift discovered Swift-Tuttle within days of each other during the Civil War in 1862! The next time this comet is expected to come into view is 2125. The shower itself seems to radiate from between Cassiopeia and Perseus constellations, which is where it gets the name, Perseid.
The meteor shower is made of meteoroids. Are there any meteorites? What is the difference?
Meteoroids are bits of rock and ice streaking hanging around in space. When meteoroids burn up in the atmosphere, giving us that incredible summer showing, then they become meteors. If a meteor makes it through the atmosphere and actually ends up on the ground, then it becomes a meteorite. Not to worry, though, that doesn't happen with the Perseids.
"Since Perseids are ice with a little dust mixed in, they never make it to the ground," said Bill Cooke, a meteoroid expert for NASA in Huntsville, Alabama.
The American Meteor Society says the trick to the best viewing is to get comfortable and wait. Sometimes the meteors won't show for five or ten minutes at a time, then you will get a cluster. Really serious folks will hop in the car and head for dark skies away from the city. This will certainly increase the activity you will see as the fainter meteors become visible. If you are really crazy, then you will count the number of Perseids you see each hour and report it to other crazy people like us at the AMS. It may be crazy, but it is fun to watch nature's fireworks. It is also scientifically useful to record this activity as it can reveal the particle density in outer space and help us predict what may occur in the years to come.