June 3, 2010 at 10:02 PM ET
Just as astronomers were telling the world that they figured out what gave Jupiter a black eye last July, yet another cosmic impact left a mark on the giant planet today. And this time, it was caught on video.
Actually, two of the world's best-known amateur observers of Jupiter both saw the flash of impact at 20:31 GMT today (4:31 p.m. ET). In Australia, Anthony Wesley captured a picture of the hit just before sunrise Friday (Down Under time). And in the Philippines, Christopher Go turned his pictures into a short video that was posted on SpaceWeather.com.
"I still can't believe that I caught a live impact on Jupiter," SpaceWeather quoted Go as saying.
It's not known exactly what caused the impact, but whether it was an asteroid or a comet, it's likely to have left a mark on Jupiter's cloud tops. So the call has gone out for all astronomers, professional and amateur, to monitor Jupiter in the hours ahead.
Great Black Spot analyzed
It was Wesley who first noticed the earlier hit on Jupiter, occurring on July 19, 2009. Actually, last year's impact occurred while the planet was turned away from Earth, so at the time, no one really knew what caused the "Great Black Spot" that persisted for months. But in the June 1 issue of The Astrophysical Journal Letters, astronomers say the culprit was likely an asteroid rather than a comet. That would make last year's impact the first time before-and-after pictures have been taken of an asteroid smashing into a planet.
To reach their conclusion, astronomers compared months' worth of Black Spot snapshots from the Hubble Space Telescope with images captured 15 years earlier, when broken-up pieces of Comet Shoemaker-Levy 9 plunged into Jupiter's atmosphere.
One team of astronomers, led by Heidi Hammel of the Colorado-based Space Science Institute, found key differences between the 1994 and the 2009 impacts. Ultraviolet imagery from 1994 revealed distinct halos around the impact sites, indicating that fine dust persisted after the impacts. The UV images also showed a strong, lingering contrast between the impact sites and the surrounding cloud cover. The astronomers took that as a sign that material from Shoemaker-Levy 9's cometary coma was hanging around in the upper cloud layers.
The aftermath of the 2009 impact, which hit with the force of thousands of nuclear bombs, was different. The UV images showed no halos, and the UV contrast quickly faded. The astronomers said the fast fade suggested that the particles left behind by last year's blast precipitated out of the clouds more rapidly. That would be "consistent with material that is more asteroidal than cometary in origin," they wrote.
NASA / ESA / Hubble Impact Team
Hubble Space Telescope snapshots show an impact scar on Jupiter fading from view over several months in 2009.
The elongated shape of last year's "Black Spot" suggested that the asteroid came in at a shallower angle than the comet did. In a separate research paper, also appearing in The Astrophysical Journal Letters, astronomers analyze traces left behind in the Black Spot to figure out the path that the asteroid might have taken to collide with Jupiter. They conclude that the object could have come from the Hilda family of small bodies, a secondary asteroid belt consisting of more than 1,100 objects orbiting near Jupiter.
Anthony Wesley, the amateur astronomer who started it all, is listed as one of the authors of that paper.
In a NASA news release, Hammel said last July's impact was a testament to the contributions made by amateur astronomers. "This event beautifully illustrates how amateur and professional astronomers can work together," she said.
Now it's time for them to work together again, in the wake of today's smashing flash.
More about Jupiter and asteroids:
Heidi Hammel is lead author of "Jupiter After the 2009 Impact: Hubble Space Telescope Imaging of the Impact-Generated Debris and Its Temporal Evolution." Other authors include M.H. Wong, J.T. Clarke, I. de Pater, L.N. Fletcher, R. Hueso, K. Noll, G.S. Orton, S. Perez-Hoyos, A. Sanchez-Lavega, A.A. Simon-Miller and P.A. Yanamandra-Fisher.
Agustin Sanchez-Lavega of the University of the Basque Country in Bilbao, Spain, is lead author of "The Impact of a Large Object on Jupiter in 2009 July." Other authors include A. Wesley, G. Orton, R. Hueso, S. Perez-Hoyos, L.N. Fletcher, P. Yanamandra-Fisher, J. Legarreta, I. de Pater, H. Hammel, A. Simon-Miller, J.M. Gomez-Forrellad, J.L. Ortiz, E. Garcia-Melendo, R.C. Puetter and P. Chodas.