[meteorite-list] Meteors from Halley's Comet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 27 Apr 2011 15:43:27 -0700 (PDT)
Message-ID: <201104272243.p3RMhRQb023089_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/science-news/science-at-nasa/2011/27apr_eta/

Meteors from Halley's Comet
NASA Science News

April 27, 2011: Looking for an adventure? Get up in the wee hours of
the morning May 6th and head out into the country, far from the city
lights. You won't be alone. The birds will be up and singing about the
coming dawn, and, of course, about the eta Aquarid meteor shower.

The eta Aquarids are best viewed from the southern hemisphere, but
there's something special about them no matter where you live: "Each eta
Aquarid meteoroid is a piece of Halley's Comet doing a kamikaze death
dive into the atmosphere," explains NASA astronomer Bill Cooke. "Many
people have never seen this famous comet, but on the morning of May 6^th
they can watch bits of it leave fiery trails across the sky."

A messenger from the dawn of the universe, Halley's Comet orbits the sun
once every 76 years. Each time it swings by the sun, intense solar heat
vaporizes about 6 meters of ice and rock from the nucleus. The debris
particles, about the size of sand grains, spread along the comet's
orbit, filling it with tiny meteoroids.

"Although Halley's Comet is deep in the outer solar system at the moment
and won't return to Earth until 2061, it treats us to a meteor shower
twice a year as our planet passes by the debris cloud," says Cooke. "In
May we have the eta Aquarids, and in October the Orionids."

And there is something especially significant about the 2011 eta Aquarids.

"This is your one chance this year to see meteors blaze across the sky
without glaring moonlight dimming them."

A thin crescent moon will vacate the sky in the early evening, leaving a
dark canvas for the display. Early risers are in luck, as the best
viewing is an hour or two before dawn. Lie down where you can see as
wide an expanse of sky as possible to catch more meteors with your
peripheral vision. Look up into the darkness and relax.

The radiant for the eta Aquarids is in the constellation Aquarius:
diagram
<https://science.nasa.gov/media/medialibrary/2011/04/26/radiant.jpg>.
But you don't need to look toward the radiant to see the meteors.

"Meteors can appear in any part of the sky," says Cooke. "In fact their
trails will tend to point back toward the radiant, so if you look that
way the meteor may appear somewhat stubby. They'll appear much longer
going by you than coming at you."

You won't need binoculars or a telescope to observe eta Aquarid meteors.
The naked eye's field of view is usually best for seeing meteors, which
frequently streak more than 45 degrees across the sky.

"Eta Aquarids are fast, moving at 66 km/s (148,000 mph!), and often
trace long paths across the sky, sometimes leaving glowing, persistent
trains. In the northern hemisphere, depending on your latitude [the
closer to the equator the better], you should see from 10 to 40 meteors
just before dawn."

Remember to pack a reclining chair or an old blanket to lie on, and a
thermos of hot coffee would be nice. After all, you'll be up mighty
early! The spring night air may be damp and chill, so bring along
another blanket--or better yet, a big furry dog, both for warmth and
company. Golden Retrievers work nicely.

It's sure to be a memorable experience. A night breeze caressing your
cheek, the aroma of hot coffee in the predawn air, a gently rising
chorus of birdsong accompanying your own personal light show -- and your
greatest admirer by your side. It just doesn't get any better.

Author: Dauna Coulter
Editor: Dr. Tony Phillips
Credit: Science at NASA

More Information

On May 5, NASA meteor experts will host an afternoon live Web chat from
2-3 p.m. Central time and an "up all night" chat from 10 p.m. on the
5^th to 4 a.m. on the 6^th (Central time). Get ready to help NASA watch
the skies! Join live Web discussion about this shower -- spawned by
Halley's Comet! -- and all things meteoric. Details here...
http://www.nasa.gov/connect/chat/aquarids2011.html
Received on Wed 27 Apr 2011 06:43:27 PM PDT