30 April 2011

See the Eta Aquarid Meteor Shower



Here's the Eta Aquarid's radiant as seen from latitude 30° north
(Houston, Cairo, Delhi, Shanghai) 90 minutes before sunrise. Farther
north, the radiant is even lower when the sky starts to get light. But
Eta Aquarids are occasionally seen as far north as the Mid-Atlantic
States.


The Eta Aquarids might be the best meteor shower that you've never heard of. This shower is caused by flecks of dust released from the nucleus of Halley's Comet. It stays near full strength for five days — longer than any comparably intense shower — and its meteors are bright and plentiful.

So why isn't it better known?

If you live in the Southern Hemisphere, where this is arguably the year's best meteor shower, you've very likely heard of it. But relatively few Eta Aquarids are visible from mid-northern latitudes, where the lion's share of amateur astronomers live. Still, this shower puts on quite a respectable show in the southernmost tier of the United States. And because the meteors are so bright, they're occasionally seen much farther north than that during morning twilight — and even broad daylight.

Conditions are ideal for the Eta Aquarids this year, because the Moon is absent from the sky during the predawn hours. The shower is forecast to peak on the morning of Friday, May 6th, with good activity from the 4th through the 8th.

As the name Eta Aquarids suggests, all of this shower's meteors appear to radiate from a spot near the northeastern corner of the constellation Aquarius. The higher a shower's radiant is in the sky, the more meteors you can see, and you won't see any meteors at all when the radiant is significantly below the horizon.

In the case of the Eta Aquarids, the radiant doesn't rise until long after midnight, and it reaches its highest in the sky well after sunrise. So the best time to watch for meteors is anywhere from one to two hours before sunrise. Earlier than that, the radiant is too low — any later, the sky is too bright.

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