The dark
bruise that appeared suddenly near the south pole of Jupiter several days ago,
likely as the result of an impact by a comet or asteroid, is as big as the Pacific Ocean, astronomers report.
The dark
spot was first
noticed by chance by amateur astronomer Anthony Wesley in Australia on Sunday, July 19.
The blemish
is thought to be the result of an impact similar to that of Comet
Shoemaker-Levy 9, which pummeled the gas giant 15 years ago.
After he
was convinced the spot was not just another storm or the shadow of one of
Jupiter's moons, Wesley alerted other astronomers around the world to the scar's
appearance.
University of California, Berkeley, astronomer
Paul Kalas took advantage of previously scheduled observing time on the Keck II
telescope in Hawaii to image the blemish in the early morning hours of Monday,
July 20. The near-infrared image showed a bright spot in the clouds of
Jupiter's southern hemisphere, where the impact had propelled reflective
particles high into the relatively clear stratosphere.
In visible
light, the bruise appears dark against the bright surface of Jupiter.
These
observations mark only the second time that astronomers have been able to see the
results of an impact on the planet, the first being Comet Shoemaker-Levy 9's
collision. Many theories were formed after that collision.
"Now
we have a chance to test these ideas on a brand new impact event," Kalas, said.
Kalas and
his colleagues hope their observations will shed light on the nature of the impact.
"The
analysis of the shape and brightness of the feature will help in determining
the energy and the origin of the impactor," said Marchis. "We don't
see other bright features along the same latitude, so this was most likely the
result of a single asteroid, not a chain of fragments like for SL9 [Comet
Shoemaker-Levy 9]."
Mike Wong,
a UC Berkeley researcher currently on leave at the Space Telescope Science
Institute in Baltimore, used the observations to calculate that the bruise is
near the southern pole of Jupiter (305 degrees west longitude and 57 degrees
south latitude in planetographic coordinates) and that the impact covers a
190-million-square-kilometer area, as big as the Pacific Ocean.
Because of
the complex shape of the explosion, it is possible that tidal effects (the
gravitational tugs of Jupiter and its moons) fragmented the impactor – a comet
or asteroid – shortly before it collided with the planet.
Later this
week, astronomers from UC Berkeley and around the world plan to conduct
high-resolution visible and ultraviolet observations of the impact site using
the Hubble Space Telescope's brand new Wide Field Camera 3. Ground-based
facilities including the W. M. Keck telescope will also use adaptive optics to
obtain much sharper infrared images of the impact's aftermath.
advertisement
