Amateur Astronomers are First to Detect Objects Impacting Jupiter

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Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

NEWS RELEASE: 2010-293B Sept. 9, 2010

AMATEUR ASTRONOMERS ARE FIRST TO DETECT OBJECTS IMPACTING JUPITER

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-293&cid=release_2010-293

PASADENA, Calif. -- Amateur astronomers using backyard telescopes were the first to detect two
small objects that burned up in Jupiter's atmosphere on June 3 and Aug. 20.

Professional astronomers at NASA and other institutions followed up on the discoveries and gathered
detailed information on the objects, which produced bright spots on Jupiter. The object that caused
the June 3 fireball was estimated to be 8 to 13 meters (30 to 40 feet) in diameter - comparable in size
to asteroid 2010 RF12 that flew by Earth on Sept. 8.

To see images and video of the two impacts, visit:
http://www.nasa.gov/topics/solarsystem/features/jupiter20100909.html .

Glenn Orton, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., will be
available for live satellite interviews today, September 9, from 2 to 6 p.m. PDT (5 to 9 p.m.
EDT). Interviews may be conducted via NASA television, and by Skype or telephone. Interested
media can call 818-393-5467 to schedule an interview.

The June 3 fireball released five to 10 times less energy than the 1908 Tunguska meteoroid, which
exploded 6 to 10 kilometers (4 to 6 miles) above Earth's surface with a powerful burst that knocked
down millions of trees in a remote part of Russia. Scientists continue to analyze the Aug. 20 fireball,
but think it was comparable to the June 3 object.

"Jupiter is a big gravitational vacuum cleaner," said Glenn Orton, an astronomer at NASA's Jet
Propulsion Laboratory in Pasadena, Calif., and co-author of a paper that will appear online Thursday
in Astrophysical Journal Letters. "It is clear now that relatively small objects that are remnants from
the formation of the solar system 4.5 billion years ago still hit Jupiter frequently. Scientists are trying
to figure out just how frequently."

The lead author of the paper in Astrophysical Journal Letters is Ricardo Hueso of the Universidad del
Pais Vasco in Bilbao, Spain.

Before amateurs spotted the June 3 impact, scientists were unaware collisions that small could be
observed. Anthony Wesley, an amateur astronomer from Australia who discovered a dark spot on
Jupiter in July 2009, was the first to see the tiny flash on June 3. Amateur astronomers had trained
their backyard telescopes on Jupiter that day because the planet was in a particularly good position for
viewing. Wesley was watching real-time video from his telescope when he saw a 2.5-second-long
flash of light near the edge of the planet.

"It was clear to me straight away it had to be an event on Jupiter," Wesley said.

Another amateur astronomer, Christopher Go, of Cebu, Philippines, confirmed 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.

Based on the data, the astronomers deduced the flash came from an object – probably a small comet
or asteroid – burning up in Jupiter's atmosphere. The object likely had a mass of about 500 to 2,000
metric tons (1 to 4 million pounds), about 100,000 times lighter than that other object that hit Jupiter
in July 2009.

The second fireball, on Aug. 20, was first detected by Japanese amateur astronomer Masayuki
Tachikawa. It flashed for about 1.5 seconds and left no debris observable by a large telescope.

"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 a few times each
month," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. "The Jupiter
impact rate is still being refined and studies like this one help to do just that."

Previous models of collisions this size on Jupiter had predicted as few as one and as many as 100 such
collisions a year. Scientists now believe the frequency must be closer to the high end of the scale.

-end-

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