August 12 - Watch the Perseid meteor shower

persied meteor shower 2012Image Credit & Copyright:APoD, Jens Hackmann

By Peter Jenniskens, Senior Research Scientist

With the Moon out of the way on Wednesday night, 12 August, the Perseid meteor shower over California is expected to be the best in 7 years.  Around 9 pm the first grazing meteors will appear, streaking away from the constellation Perseus. Rates and apparent speeds will pick up around 1 am Thursday morning, peaking at a little more than 80 per hour just before dawn, after 5 am.

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If you’ve been following this shower since it first became conspicuous in mid-July, when the radiant was actually in Cassiopeia, you may have noticed that not all of the fast meteors from that direction were Perseids. During its business meeting on Monday, 10 August, old Commission 22 of the International Astronomical Union — in its last official act before giving way to new Commission F1 — added 18 showers to the list of established ones at the IAU Meteor Data Center and moved one back to the working list for more study, bringing the tally of well-established meteor showers to 112. One of the 18 new showers is called the 49 Andromedids, with IAU code FAN. The shower sits amidst other streams that may, or may not, share a common origin at Comet 109P/Swift-Tuttle. How these streams came about can now become a topic of active research by any fan of the Perseids. 

In the diagram on the right, the newly established 49 Andromedids (FAN) appear as a cloud of radiant points, i.e., directions from which the meteoroids are approaching us, in this plot made during the period 7–28 July. Data are drift corrected for Earth’s motion around the Sun. The new shower appears amidst the Perseids (PER), Cassiopeiaids (ZCS), and c Andromedids (CAN).