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Meteors

Perseids of August

Jane Houston Jones


August Perseids! Here are the active dates and peak dates:

Activity from this meteor shower is visible from about July 23 until August 22. At the time of maximum on August 12/13 (J2000 solar longitude=139.7 deg), the radiant is located at R.A. 47 deg, Decl. +57 deg. The hourly rate typically reaches 80, although some years have been as low as 4 and as high as 200. The meteors tend to be very fast, with an average magnitude of 2.3, and about 45% leave persistent trains. The radiant advances by a rate of 1.40 deg/day in right ascension and 0.25 deg/day in declination.

To best observe the Perseids wear appropriate clothing for the weather. Lay outside in a reclining lawn chair with your feet pointing southward and look straight up. Do not look directly at the radiant, because meteors directly in front of you will not move much and fainter ones might be missed. Decent numbers of Perseids can be seen beginning around 10 p.m. local time, but the best show picks up after midnight and continues until dawn. When you see a meteor mentally trace it backwards and if you arrive at Perseus it is probably a Perseid.

In addition to the main radiant near Eta Persei, there are 4 minor ones. The radiants of these for minor showers are near Chi and Gamma Persei, and Alpha and Beta Persei. These meteor showers are generally short-lived and possess radiants that move nearly parallel to the main radiant. The following are summaries of the most consistent of the secondary Perseid radiants.

The Gamma Perseids mainly occur during August 11 to 16 from an average radiant of R.A. 41 deg, Decl. +55 deg. The radiant diameter averages about 2 deg. Rates rise and decline with those of main radiant.

The Chi Perseids occur during August 7 to 16 from an average radiant of R.A. 35 deg, Decl. +56 deg. The radiant diameter is about 2 deg. Maximum seems to occur between the 9th and 11th.

The Alpha Perseids occur during August 7 to 24 from an average radiant of R.A. 51 deg, Decl. +50 deg. The radiant diameter averages about 1.5 deg. Maximum seems to occur somewhere between the 12th and 17th.

The Beta Perseids occur during August 12 to 18 from an average radiant of R.A. 47 deg, Decl. +40 deg. The radiant diameter averages about 1 deg. Rates are irregular. Weakest branch of the Perseid cluster.

If you need a chart to find Perseus, refer to last month's meteor column, or look at any star chart.


Mail to: Jane Houston Jones
Copyright © 2000 San Jose Astronomical Association
Last updated: July 19, 2007

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