Tuesday, August 18, 2009

Perseids

This is the most famous of all meteor showers. It never fails to provide an impressive display and, due to its summertime appearance, it tends to provide the majority of meteors seen by non-astronomy enthusiasts.

This meteor shower gets the name "Perseids" because it appears to radiate from the constellation Perseus. An observer in the Northern Hemisphere can start seeing Perseid meteors as early as July 23, when one meteor every hour or so could be visible. During the next three weeks, there is a slow build-up. It is possible to spot five Perseids per hour at the beginning of August and perhaps 15 per hour by August 10. The Perseids rapidly increase to a peak of 50-80 meteors per hour by the night of August 12/13 and then rapidly decline to about 10 per hour by August 15. The last night meteors are likely to be seen from this meteor shower is August 22, when an observer might see a Perseid every hour or so.

For observers in the Southern Hemisphere, the Perseid radiant never climbs above the horizon, which will considerably reduce the number of Perseid meteors you are likely to see. Nevertheless, on the night of maximum, it is possible to see 10-15 meteors per hour coming up from the northern horizon.

There are other, weaker meteor showers going on around the same time as the Perseids, but the Perseids will generally appear to move much faster across the sky than meteors from the other showers. In fact, the Perseids are among the fastest moving meteors we see every year. Another way to know if the meteor you saw was a Perseid is to mentally trace the meteor backwards. If you end up at Perseus then you have probably seen a Perseid meteor! If you are not sure where Perseus is in the sky, the following charts will help you find it from both the Northern Hemisphere and Southern Hemisphere:

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