From Denny: Every August we night sky watchers get to enjoy the Perseid meteor showers. This year it's supposed to be spectacular with hundreds whizzing by in the sky for our enjoyment. It peaks from midnight to dawn. In my area there will probably be cloud cover like most years but I'm still getting up in the middle of the night hoping to catch a glimpse. Hot and humid Louisiana is not exactly the best viewing of astronomical events. :)
Meteor showers are made up of what?
This famous meteor shower is actually the exhaust plume of the comet called 109/Swift-Tuttle. We really have to work on getting scientists to employ a Romance era English professor - who secretly writes modern day romance novels on the side for outrageous income - to come up with some better and more creative names.
So here's what happens as this ST comet enters the inner solar system. As it whips around the sun it starts heating up. The ice pockets on the comet melt, pretty much skip the liquid stage just for fun, and turn into gas. Those ice pockets also spew out dust and rock chunks as the ice is coming loose. Like any good drama queen exiting the stage, as this comet exits the inner solar system, there is still the long train of a debris trail that remains for our Earth to pass through. And we on Earth find this process terribly romantic as we gaze up toward the heavens.
Planet Earth started its move into Swift-Tuttle’s stream of dust by the middle of July. "The debris is a very old stream that has been building for a long time and is a very dense concentration of dust," says Peter Jenniskens, a meteor researcher at the SETI Institute in Mountain View, Calif.
"Indeed, if you look back at records from the Middle Ages, you can see that people in the Middle Ages were seeing the Perseid meteor shower," he says. This year the Perseid shower is trumpeted to be above average.
How much will you see?
Under the best of conditions this meteor shower may generate up to 100 meteors an hour. It all depends upon just how dark your skies are going to be so you have to know your area. If you are in an area where you can hike up to the top of a mountain you can expect to see up to 108 meteors an hour. The peak viewing hours are from 3 AM to 4 AM Eastern Standard Time. And the official word is too that our night sky will be having a double feature: a waning-gibbous moon. Read that as it's a new moon so the Perseid shower won't have to compete with a lot of moonlight.
"Earth will be passing through a denser patch of Swift-Tuttle's dust stream than usual," according to William Cooke, who heads NASA's Meteroid Environment Office at the Marshall Spaceflight Center in Huntsville, Alabama. "The main dust stream got a slight stir from Saturn, and we're also running into a patch of material the comet off-loaded in 1479," Cooke explains.
Why called the Perseid shower?
The meteors appear to be emerging from the area of the night sky that contains the constellation Perseus. For some good advice of how to photograph this event and some more detailed viewing tips check out the American Meteor Society's website.
Check out the "Fluxtimator." You can check out what is likely to happen in your area for meteor showers besides this August show of the Perseid. The graph will automatically adjust itself to give you the best viewing times for your location when you select which meteor shower, your nearest major urban area, your viewing conditions and the date. It will even tell you how many of those famous shooting stars you are likely to see.
If your alarm clock fails to rouse you tonight, don't worry. You still have a chance the next morning at about the same times.
History of the Swift-Tuttle comet
This comet was discovered as far back in history as 1862 by two astronomers: Lewis Swift and Horace Tuttle. They both saw this comet within days of each other. I guess they agreed to both claim bragging rights - so the astronomy community decided to split the difference and name the comet after both of them.
This comet swings around our sun once in every 133.28 years. The last time we saw it was back in 1992 and it will return again in 2126, assuming we all survive the Mayan predictions of 2012. Astronomers at NASA's Jet Propulsion Laboratory are pretty excited about the next visit. They say it should be spectacular because the comet will pass so close to Earth, by a distance of only 14 million miles.
The Oort cloud is where the Swift-Tuttle comet originated. The Oort cloud is this huge spherically shaped cloud made up of frozen leftovers from when the solar system was formed, about 4.6 billion years ago. The word is that when the ST comet was passing through the inner solar system that planet Jupiter took an interest and captured it. After that event about 160,000 years ago the comet's orbit around the sun shrank.
While Jupiter was successful at rounding up this comet into the zone Jupiter's gravity was not able to reel in this comet to become part of the short-period comets stable. Those guys reappear about every 20 years or even in less time. This ST comet proved difficult to tame and joined the ranks of comets like Halley's Comet, having an orbital period that could range from 20 to 200 years.
Every time the ST comet tours through the inner solar system it makes a teasing pass across Jupiter's orbit. Yet it manages to remain just out of reach of grasping Jupiter so the ST comet's travel plans and path are never significantly altered. This is one crafty stealthy comet determined to remain free to do as it will. One thing is for sure is that every time the ST comet passes by it slowly thickens that famous dust stream it leaves behind for us all on Earth to admire.
The best place to view this comet will be in the Northern Hemisphere. Yeah, since I live in south Louisiana on the Gulf of Mexico I only get to view about 30 to 40 meteors an hour - and that's at the peak. It's still worth the spectacular view in the wee hours of the morning.
To enjoy your night out watching the sky for free from the University of Texas's McDonald Observatory:
* Try to drive out to a safe and secure dark spot outside your city or town where you can reduce the light pollution that will interfere with your viewing. Be sure to arrive early enough to allow for your eyes to adjust to the dark. Here in Louisiana we do have a small observatory in a large park setting where city residents go for these events.
* Make sure you have a low horizon to the northeast. This is where the constellation Perseus will rise.
* Either lay on a blanket or a chaise lounge you've brought just for this purpose (you plan-ahead person, you) and position yourself so the horizon is just within your peripheral vision. Since Perseus moves across the night sky, be ready to tweak your viewing position as it does so.
* As the folks at the observatory say: "Treat meteor watching like you would the 4th of July fireworks. Pack comfortable chairs, bug spray, food and drinks, blankets, plus a red-filtered flashlight for reading maps and charts without ruining your night vision. Binoculars are not necessary. Your eyes will do just fine."
* If you need a quick red filter for your flashlight, try picking up a tail-light repair kit from your local auto-parts store. The red plastic works well and is fairly easy to cut.
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Astronomers and the night sky Photo by Peter Petrov
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