Fireballs Light Up Jupiter Sept. 9, 2010:  In a paper published today in the   
   Astrophysical Journal Letters, a group of professional and amateur astronomers   
   announced that Jupiter is getting hit surprisingly often by small asteroids,   
   lighting up the giant planet's atmosphere with frequent fireballs. [...]   
   View a movie of the June 3rd impact recorded by Christopher Go of Cebu City,   
   the Philippines. "Jupiter is a big gravitational vacuum cleaner," says   
   co-author and JPL astronomer Glenn Orton. "It is clear now that relatively   
   small objects left over from the formation of the solar system 4.5 billion   
   years ago still hit Jupiter frequently."   
       
   The impacts are bright enough to see through backyard telescopes on Earth.   
   Indeed, amateur astronomers were the first to detect them, recording two   
   fireballs in 2010 alone-one on June 3rd and another on August 20th.   
       
   Professional astronomers at NASA and elsewhere have followed up on the amateur   
   observations, hoping to learn more about the impacting bodies. According to   
   today's Letter, first-authored by Ricardo Hueso of the Universidad del Pa¡s   
   Vasco in Spain, the June 3rd fireball was caused by an object some 10 meters   
   in diameter. When it hit Jupiter, the impact released about one thousand   
   million million (10^15) Joules of energy. For comparison, that's five to ten   
   times less energy than the "Tunguska event" of 1908, when a meteoroid exploded   
   in Earth's atmosphere and leveled millions of trees in a remote area of   
   Russia. Scientists continue to analyze the Aug. 20th fireball, but think it   
   was comparable in scale to the June 3rd event.   
       
   Before amateurs spotted these fireballs, scientists were unaware collisions so   
   small could be observed. The first hint of their easy visibility came in July   
   2009 when Anthony Wesley, an amateur astronomer from Australia, discovered a   
   dark spot on Jupiter. It was clearly the swirling debris of an impact event   
   that he had only just missed. Next time, however, his luck would improve. On   
   June 3, 2010, he caught a fireball in action.   
   [...]   
   A color composite image of the June 3rd Jupiter impact flash. Credit: Anthony   
   Wesley observing from Broken Hill, Australia. [more]   
       
   "I was watching real-time video from my telescope when I saw a 2.5-second-long   
   flash of light near the edge of Jupiter's disk," says Wesley. "It was clear to   
   me straight away it had to be an event on Jupiter."   
       
   Another amateur astronomer, Christopher Go of the Philippines, confirmed that   
   the flash also appeared in his recordings. Professional astronomers, alerted   
   by email, looked for signs of the impact in images from larger telescopes,   
   including NASA's Hubble Space Telescope, the European Southern Observatory's   
   Very Large Telescope in Chile, and Gemini Observatory telescopes in Hawaii and   
   Chile. Scientists saw no thermal disruptions or typical chemical signatures of   
   debris, which allowed them to put a limit on the size of the object.   
   [...]   
   The Aug. 20th fireball recorded by Aoki Kazuo of Tokyo, Japan. The second   
   fireball on Aug. 20th was first detected by Japanese amateur astronomer   
   Masayuki Tachikawa of Kumamoto city and quickly confirmed by another Japanese   
   amateur, Aoki Kazuo of Tokyo. This one flashed for about 1.5 seconds and, like   
   the June 3rd fireball, left no debris observable by large telescopes.   
       
   "It is interesting to note that while Earth gets smacked by a 10-meter-sized   
   object about every 10 years on average, it looks as though Jupiter gets hit   
   with the same-sized object [as much as] a few times each month," comments Don   
   Yeomans, manager of the Near-Earth Object Program Office at JPL, who was not   
   directly involved in the study.   
       
   Learning how often Jupiter is hit can tell astronomers something about the   
   meteoroid population throughout the solar system-a matter of considerable   
   interest right here on Earth.  Just yesterday on Sept. 8th, a 10-meter class   
   asteroid named 2010 RF12 flew past our planet without hitting.  A somewhat   
   smaller space rock, 2008 TC3, actually burned up in the atmosphere above Sudan   
   two years ago.   
       
   "The Jupiter impact rate is still being refined," adds Yeomans, "and studies   
   like this one help to do just that."   
       
   To learn more about the original research, read "First Earth-based Detection   
   of a Superbolide on Jupiter" by R. Hueso et al, in the Ap J Letters, 2010,   
   721, L129   
       
   Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Jupiter Impact: Mystery of the Missing Debris -- (Science@NASA)   
       
   What Hit Jupiter? -- (Science@NASA)   
       
   Jupiter Loses a Stripe -- (Science@NASA)   
       
   Caught in the Act, Fireballs Light up Jupiter -- (JPL)   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.54   
    * Origin: NCS BBS (1:3828/7)