Meteors from Halley's Comet   
       
   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 6th they can watch bits of it   
   leave fiery trails across the sky."   
   [...]   
   Click on the image to view a ScienceCast video about the eta Aquarid meteor   
   shower.   
       
   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.   
   [...]   
   A NASA fireball camera at the Marshall Space Flight Center caught this eta   
   Aquarid meteor in flight in May 2009. [movies: avi, Quicktime]   
       
   The radiant for the eta Aquarids is in the constellation Aquarius: diagram.   
   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@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 5th  to 4   
   a.m. on the 6th (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/cha   
   /aquarids2011.html   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.6   
    * Origin: NCS BBS (1:3828/7)