The Fireballs of February   
       
   Feb. 22, 2012:  In the middle of the night on February 13th, something   
   disturbed the animal population of rural Portal, Georgia. Cows started mooing   
   anxiously and local dogs howled at the sky. The cause of the commotion was a   
   rock from space.   
       
   "At 1:43 AM Eastern, I witnessed an amazing fireball," reports Portal resident   
   Henry Strickland. "It was very large and lit up half the sky as it fragmented.   
   The event set dogs barking and upset cattle, which began to make excited   
   sounds. I regret I didn't have a camera; it lasted nearly 6 seconds."     
   Strickland witnessed one of the unusual "Fireballs of February."   
       
   A fireball over north Georgia recorded on Feb. 13th by a NASA all-sky camera   
   in Walker Co., GA. [video]   
       
   "This month, some big space rocks have been hitting Earth's atmosphere," says   
   Bill Cooke of NASA's Meteoroid Environment Office. "There have been five or   
   six notable fireballs that might have dropped meteorites around the United   
   States."   
       
   It's not the number of fireballs that has researchers puzzled. So far,   
   fireball counts in February 2012 are about normal. Instead, it's the   
   appearance and trajectory of the fireballs that sets them apart.   
       
   "These fireballs are particularly slow and penetrating," explains meteor   
   expert Peter Brown, a physics professor at the University of Western Ontario.   
   "They hit the top of the atmosphere moving slower than 15 km/s, decelerate   
   rapidly, and make it to within 50 km of Earth's surface."   
       
   The action began on the evening of February 1st when a fireball over central   
   Texas wowed thousands of onlookers in the Dallas-Fort Worth area.   
       
   "It was brighter and long-lasting than anything I've seen before," reports   
   eye-witness Daryn Morran. "The fireball took about 8 seconds to cross the sky.   
   I could see the fireball start to slow down; then it exploded like a   
   firecracker artillery shell into several pieces, flickered a few more times   
   and then slowly burned out." Another observer in Coppell, Texas, reported a   
   loud double boom as "the object broke into two major chunks with many smaller   
   pieces."   
       
   The fireball was bright enough to be seen on NASA cameras located in New   
   Mexico more than 500 miles away. "It was about as bright as the full Moon,"   
   says Cooke. Based on the NASA imagery and other observations, Cooke estimates   
   that the object was 1 to 2 meters in diameter.   
       
   So far in February, NASA's All-Sky Fireball Network has photographed about a   
   half a dozen bright meteors that belong to this oddball category. They range   
   in size from basketballs to buses, and all share the same slow entry speed and   
   deep atmospheric penetration. Cooke has analyzed their orbits and come to a   
   surprising conclusion:   
       
   This camera is part of NASA's All-Sky Fireball Network. [more] "They all hail   
   from the asteroid belt-but not from a single location in the asteroid belt,"   
   he says. "There is no common source for these fireballs, which is puzzling."   
       
   This isn't the first time sky watchers have noticed odd fireballs in February.   
   In fact, the "Fireballs of February" are a bit of a legend in meteor circles.   
       
   Brown explains: "Back in the 1960s and 70s, amateur astronomers noticed an   
   increase in the number of bright, sound-producing deep-penetrating fireballs   
   during the month of February. The numbers seemed significant, especially when   
   you consider that there are few people outside at night in winter. Follow-up   
   studies in the late 1980s suggested no big increase in the rate of February   
   fireballs. Nevertheless, we've always wondered if something was going on."   
       
   Indeed, a 1990 study by astronomer Ian Holliday suggests that the 'February   
   Fireballs' are real. He analyzed photographic records of about a thousand   
   fireballs from the 1970s and 80s and found evidence for a fireball stream   
   intersecting Earth's orbit in February. He also found signs of fireball   
   streams in late summer and fall. The results are controversial, however. Even   
   Halliday recognized some big statistical uncertainties in his results.   
       
   NASA's growing All-Sky Fireball Network could end up solving the mystery.   
   Cooke and colleagues are adding cameras all the time, spreading the network's   
   coverage across North America for a dense, uninterrupted sampling of the night   
   sky.   
       
   "The beauty of our smart multi-camera system," notes Cooke, "is that it   
   measures orbits almost instantly. We know right away when a fireball flurry is   
   underway-and we can tell where the meteoroids came from." This kind of instant   
   data is almost unprecedented in meteor science, and promises new insights into   
   the origin of February's fireballs.   
       
   Meanwhile, the month isn't over yet. "If the cows and dogs start raising a   
   ruckus tonight," advises Cooke, "go out and take a look."   
       
       
   Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
   More Information   
   NASA astronomer Bill Cooke is head of the Meteoroid Environment Office   
       
   NASA's All-Sky Fireball Network   
       
   Peter Brown -- Meteor Physics Group, University of Western Ontario   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.75   
    * Origin: NCS BBS (1:3828/7)