The University of Arizona

Perseid Peaks Late This Week

By Jeff Harrison, University Communications | August 10, 2010

Debris from comet Swift-Tuttle will fly into the upper atmosphere in one of the best meteor showers of the year.

Perseid meteor
Perseid meteor

With the weather clearing this week, Arizonans likely will get a good chance to see one of the best meteor showers of the year.

The Perseid Meteor Shower occurs about this time every August when Earth's orbit around the sun takes it through debris left behind by the comet Swift-Tuttle.

"If you've never seen a meteor, this is the week to see one," said University of Arizona senior research scientist Carl Hergenrother at the Lunar and Planetary Laboratory. At its peak, the Perseids can produce about 60 meteors per hour.

Swift-Tuttle, a Halley-type comet, orbits the sun roughly once every 135 years. American astronomers Lewis A. Swift and Horace P. Tuttle independently identified it in 1862. Ancient records indicate the comet was first seen in 68 BC, and it was last here in 1992.

Hergenrother, whose cameras are part of the video observations compiled for the AKM/IMO Video Meteor Network, said while the best viewing is Thursday morning, the debris cloud has actually been producing meteors since July and will continue throughout August

"During most of this time, the Earth was encountering dust released approximately over the past 15,000-plus years. Most of this ancient dust never crosses the Earth's orbit so Perseid rates remain low, at best five to 10 meteors per hour," he said. "This week we encounter dust released more recently, within the past 5,000 years. Since the comet's orbit over the past few thousands of years has intersected the Earth's, we will see a large increase in meteor rates this week."

"The last two years have also seen a number of spikes in activity on one or two nights around the predicted peak," Hergenrother said. "What this means is that high Perseids numbers can happen at any time, even tens of hours before or after the predicted peak. This year will see passage near a few older trails, which may enhance the number of meteors by five to 10 per hour."

This shower is called the Perseids is because meteors appear to radiate from a point (called the radiant) in the constellation of Perseus, located low in the northeastern sky. Late in the night, the radiant will be located just north of overhead. You don't have to look directly at the radiant. Meteors will be visible all over the sky and it is usually best to look about 45-90 degrees away from the radiant.

He said while the radiant will be visible for nearly the entire night, it will be too low in the sky to produce high numbers of meteors until after midnight. The later in the night you observe, the greater the number of meteors. By 3-4 a.m., the radiant is nearly overhead.

The best views are away from city lights. Overnight lows in the desert will be warm, and cooler in the mountains. Hergenrother said he'll be wearing long pants and a long-sleeved shirt to help thwart mosquitos and other bugs.

Contacts

Carl Hergenrother

Lunar and Planetary Laboratory

520-626-5364

chergen@lpl.arizona.edu (best way to contact)