May 4, 2009 - Forecasters expect the 2009 eta Aquarid shower to peak on Wednesday morning, May 6th, with as many as 85 meteors per hour over the southern hemisphere. Sky watchers in Australia, New Zealand, South America and southern Africa are favored. Rates in the northern hemisphere will be less, 20 to 30 per hour. The best time to look is during the moonless hour before local sunrise. That is when the shower's radiant is high in the sky and the nearly-full Moon will have set, leaving the sky dark for meteors.
Eta Aquarids are flakes of dust from Halley's Comet, which last visited Earth in 1986. Although the comet is now far away, beyond the orbit of Uranus, it left behind a stream of dust. Earth passes through the stream twice a year in May and October. In May we have the eta Aquarid meteor shower, in October the Orionids. Both are caused by Halley's Comet.
The shower is named after a 4th-magnitude star in the constellation Aquarius. The star has nothing to do with the meteor shower except that, coincidentally, meteors appear to emerge from a point nearby. Eta Aquarii is 156 light years from Earth and 44 times more luminous than the Sun.
The constellation Aquarius does not rise very far above the horizon in the northern hemisphere, and that's why northerners see relatively few meteors. But the ones they do see could be spectacular Earthgrazers.
Earthgrazers are meteors that skim horizontally through the upper atmosphere. They are slow and dramatic, streaking far across the sky. The best time to look for Earthgrazers is between 2:00 to 2:30 a.m. local time when Aquarius is just peeking above the horizon.
Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will point back toward Aquarius.
Tidbits:
* Eta Aquarid meteoroids hit Earth's atmosphere traveling 66 km/s.
* Typical eta Aquarid meteors are as bright as a 3rd magnitude star.
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