Two fireballs that struck Jupiter this summer may have given the skywatchers who spotted them a great show, but the cosmic crashes also packed a punch on the gas giant.
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. Since then, the skywatchers teamed up with professional astronomers to study the fireballs, which were likely caused by rogue asteroids or comets.
"Jupiter is a big gravitational vacuum cleaner," said study co-author Glenn Orton, a co-author of the paper and an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It is clear now that relatively small objects, remnants of the formation of the solar system 4.5 billion years ago, still hit Jupiter frequently. Scientists are trying to figure out just how frequently." [Video: Fireballs Light Up Jupiter]
The object that caused the June 3 fireball was 30 to 40 feet wide (8 to 13 meters). The object is comparable in size to the asteroid 2010 RF12 that flew by Earth Wednesday, and slightly larger than the asteroid 2008 TC3, which burned up above Sudan two years ago.
The energy released by the June 3 fireball as it collided with Jupiter's atmosphere was between a fifth and a tenth of the 1908 Tunguska event on Earth, which knocked over tens of millions of trees in a remote part of Russia.
Analysis is continuing on the Aug. 20 fireball, but scientists said it was comparable to the June 3 object.
The June 3 fireball was spotted by skywatchers Anthony Wesley in Australia, and Christopher Go in Cebu, Philippines. The Aug. 20 event was first observed by Japanese amateur astronomer Masayaki Tachikawa and later confirmed by Aoki Kazuo and Masayuki Ishimaru.
The amateur astronomers worked with a team of pros led by researcher Ricardo Hueso, of the Universidad del País Vasco, Bilbao, Spain, to determine the size of the fireballs.
The research is detailed in the Sept. 9 edition of the Astrophysical Journal Letters.