Some Comets like it Hot   
       
   Jan. 12, 2012: Comets are icy and fragile. They spend most of their time   
   orbiting through the dark outskirts of the solar system safe from destructive   
   rays of intense sunlight.  The deepest cold is their natural habitat.   
       
   Last November amateur astronomer Terry Lovejoy discovered a different kind of   
   comet.  The icy fuzzball he spotted in the sky over his backyard observatory   
   in Australia was heading almost directly for the sun.  On Dec. 16th, less than   
   three weeks after he found it, Comet Lovejoy would swoop through the sun's   
   atmosphere only 120,000 km above the stellar surface.   
       
   Astronomers soon realized a startling fact: Comet Lovejoy likes it hot.   
       
   "Terry found a sungrazer," says Karl Battams of the Naval Research Lab in   
   Washington DC.  "We figured its nucleus was about as wide as two football   
   fields-the biggest such comet in nearly 40 years."   
       
   http://spaceweather.com/comets/gallery_lovejoy_page2.htm   
       
   Comet Lovejoy at sunrise on Dec. 25, 2011. Wayne England took the picture from   
   Poocher Swamp, west of Bordertown, South Australia. [more]   
       
   Sungrazing comets aren't a new thing. In fact, the orbiting Solar and   
   Heliospheric Observatory (SOHO) watches one fall toward the sun and evaporate   
   every few days. These frequent kamikaze comets, known as "Kreutz sungrazers,"   
   are thought to be splinters of a giant comet that broke apart hundreds of   
   years ago.  Typically they measure about 10 meters across, small, fragile, and   
   easily vaporized by solar heat.   
       
   Based on its orbit, Comet Lovejoy was surely a member of the same   
   family-except it was 200 meters wide instead of the usual 10.  Astronomers   
   were eager to see such a whopper disintegrate.  Even with its extra girth,   
   there was little doubt that it would be destroyed.   
       
   When Dec. 16th came, however, "Comet Lovejoy shocked us all," says Battams.   
   "It survived, and even flourished."   
       
   Images from NASA's Solar Dynamics Observatory showed the comet vaporizing   
   furiously as it entered the sun's atmosphere--apparently on the verge of   
   obliteration-yet Comet Lovejoy was still intact when it emerged on the other   
   side.  The comet had lost its tail during the fiery transit--a temporary   
   setback. Within hours, the tail grew back, bigger and brighter than before.   
       
   "It's fair to say we were dumbfounded," says Matthew Knight of the Lowell   
   Observatory and the Johns Hopkins Applied Physics Lab. "Comet Lovejoy must   
   have been bigger than we thought, perhaps as much as 500 meters wide."   
       
   That would make it the biggest sungrazer since Comet Ikeya-Seka almost 40   
   years ago.  With a tail that stretched halfway across the sky, Ikeya-Seki was   
   actually visible in broad daylight after it passed through the sun's   
   atmosphere in October 1965. In Japan, where observers spotted the over-heated   
   comet only 1/2 degree from the sun, it was described as 10 times brighter than   
   the Full Moon.   
       
   Comet Lovejoy wasn't that bright, but it was still amazing. Only a few days   
   after it left the sun, the comet showed up in the morning skies of the   
   southern hemisphere.  Observers in Australia, South America, South Africa, and   
   New Zealand likened it to a search light beaming up from the east before   
   dawn.  The tail lined up parallel to the Milky Way and, for a few days, made   
   it seem that we lived in a double-decker galaxy.   
       
   http://spaceweather.com/comets/lovejoy_16dec11/EUVI_B_lovejoy.gif   
       
   This sequence of images, gathered by an extreme UV telescope onboard NASA's   
   STEREO-B spacecraft, shows Comet Lovejoy's tail wiggling wildly in transit   
   through the solar corona. [animation]   
       
   Astronauts on the International Space Station also witnessed the comet. ISS   
   Commander Dan Burbank, who has seen his share of wonders, even once flying   
   directly through the Northern Lights onboard the space shuttle, declared Comet   
   Lovejoy "the most amazing thing I have ever seen in space."   
       
   An armada of spacecraft including SOHO, the Solar Dynamics Observatory, NASA's   
   twin STEREO probes, Japan's Hinode spacecraft, and Europe's Proba2   
   microsatellite recorded the historic event.   
       
   "We've collected a mountain of data," says Knight. "But there are some things   
   we're still having trouble explaining."   
       
   For instance, what made Lovejoy's tail wiggle so wildly when it entered the   
   solar corona?  Perhaps it was in the grip of the sun's powerful magnetic field.   
       
   What caused Lovejoy to lose its tail inside the sun's atmosphere-and then   
   regain it later? "This is one of the biggest mysteries to me," says Battams.   
       
   And then there is the ultimate existential puzzle: How did Comet Lovejoy   
   survive at all?   
       
   As January unfolds, the "Comet that liked it Hot" is returning to the outer   
   solar system, still intact, leaving many mysteries behind.  "It'll be back in   
   about 600 years," says Knight.  "Maybe we will have figured them out by then."   
       
       
   Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More Information   
       
   Comet Lovejoy Plunges into the Sun and Survives -- Science@NASA   
       
   ISS images of Comet Lovejoy   
       
   Comet Lovejoy Photo Gallery -- amateur images from spaceweather.com   
       
   more images of Comet Lovejoy -- a gallery of spacecraft images assembled by   
   NASA's Heliophysics Division   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.72   
    * Origin: NCS BBS (1:3828/7)