Active: July 17-August 24
Peak: August 12, 20:15 UT
Dark of the Moon will be August 8^th which will improve visibility.

PERSEIDS (maximum August 12, 23h UT [4pm PDT])

Over the next few days Earth will sweep through the debris trail of an ancient comet named Swift-Tuttle. Thousands of bits of dust and rock will crash into our planet's atmosphere, lighting up the night skies with dozens of flashing meteors per hour. This spectacular event is known as the Perseid meteor shower, and it usually provides the best meteor show of the year.

The Perseids are, without a doubt, the most popular annual shower for NW observers. The often warm and clear weather, combined with the Perseids' reliably high rates and long shower duration, make this stream an ideal if non-representative introduction to meteor observing.

A few Perseids are visible starting in mid-July, when the radiant is far from Perseus in Cassiopeia. During the last week of July, 2001 observations indicated Perseid rates of about 3/hour. By August 7, they exceed 10. On August 11 a steep increase begins, with rates rising from 20/hour to about 50/hour on the morning of August 12. The maximum occurs during daylight this year for the West Coast. Late on the evening of August 12, at the end of evening twilight, the rate should still be around 80. Observed rates will initially be around 30/hour due to low radiant elevation, but may climb to 50-60/hour in the morning hours of August 13. On the morning of August 14, rates should be around 30/hour.

This is what to expect from the Perseids, but it is important to note that few meteor showers perform exactly as expected. That is why amateur data continues to be valuable. With mostly Moon-free conditions surrounding the Perseid peak (the waxing crescent sets at around 10:50pm on August 12), this shower should be attractive to new meteor counters. Remember that the best rates will occur in the hours just before morning twilight (although anytime after midnight is a good time to watch, and the entire night of August 12/13 should be monitored closely). Sporadic (non-Perseid) rates will be high (10-20/hour) and will add greatly to the display.

On an Average Day . . .

While the average counting rate of meteors for the entire sky is between 5 and 10 per hr, an observer may see twice this number in one part of the sky during a shower, and in the case of the Perseids, possibly more than 100 in an hour. Meteor showers are closely associated with comets.

When a comet breaks up, a swarm of particles eventually becomes scattered out over its entire orbit. If this orbit intersects that of the earth, a meteor shower will be observed. The shower will be particularly intense in those years when the original comet would have been observed.

The trail of a comet . . .

A comet is little more than a collection of frozen gas and loose rubble -- most of it dust particles and small rocks. As the comet sweeps around in its orbit it is constantly shedding material. Over time, its orbit becomes a "racetrack" littered with its scattered debris.

There are hundreds of comets known, and most of them have orbits that never come near Earth. But a few comets have orbits that do cross Earth's orbit, which means that once a year our planet crashes through the debris trail those comets have left behind. When that happens we experience a meteor shower, a night or two when flurries of meteors are seen, apparently emanating from a specific section of the night sky.

The Perseid meteor shower in August of each year is associated with Comet Swift-Tuttle, a well-known comet that has a 134-year orbit and was last near the sun in 1992. The debris it has left on its orbital path is what makes up the meteors of the Perseid shower.

Some Links

http://www.ticetboo.demon.co.uk/perseids.htm

http://homepage2.nifty.com/~baron/per02p.htm

http://www.imo.net/calendar/cal02.html