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Astronomers: impact gives Jupiter bruise as wide as Pacific

July 22, 2009
Courtesy 
and World Science staff

Some­thing seems to have slammed in­to Ju­pi­ter in the last few days, cre­at­ing a dark bruise about the size of the Pa­cif­ic Ocean, as­tro­n­o­mers say.

The bruise was no­ticed by an am­a­teur as­tron­o­mer on July 19, and pro­fes­sion­al as­tro­nom­ers fol­lowed suit. Un­ivers­ity of Cal­i­for­nia at Berke­ley re­search­er Paul Kalas used the Keck II tel­e­scope in Ha­waii to im­age the blem­ish in the early morn­ing the next day. 

As­tro­no­mers re­leased this im­age of the scar from a "probable" as it ap­peared Ju­ly 19 in Ju­pi­ter's south­ern hem­i­sphere. This in­fra­red im­age tak­en with Keck II on Ju­ly 20 shows the new fea­ture ob­served on Ju­pi­ter and its rel­a­tive size com­pared to Earth. (Cred­it: Paul Kalas (UCB), Mi­chael Fitz­ger­ald (LLNL/U­CLA), Franck Marchis (SETI In­sti­tute/UCB), James Gra­ham (UCB))

The im­age in near-in­fra­red light showed a bright spot in the south­ern hem­i­sphe­re, a sign of re­flec­tive par­t­i­cles float­ing high in Ju­pi­ter’s sky, sci­en­tists said. In vis­i­ble light, the bruise looks dark against the bright sur­face of Ju­pi­ter.

“This was most likely the re­sult of a sin­gle as­ter­oid,” said as­tron­o­mer Frank Mar­chis at Berke­ley.

The Keck ob­serva­t­ion marks only the sec­ond time as­tron­o­mers have seen the re­sults of an im­pact on the plan­et. The first oc­curred 15 years ago, be­tween July 16 and 22, 1994, when more than 20 frag­ments of com­et Shoe­ma­ker-Levy 9 col­lid­ed with Ju­pi­ter.

The Shoemaker-Levy 9 im­pacts were well-stud­ied by as­tron­o­mers, and many the­o­ries were sub­se­quently de­vel­oped based on the ob­serva­t­ions. “Now we have a chance to test these ideas on a brand new im­pact,” said Kalas, who with col­leagues watched the af­ter­math of the new 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” as with Shoe­ma­ker-Levy 9.

“The fact that [the fea­ture] shows up so clearly means that it’s as­so­ci­at­ed with high-altitude aerosols, as seen in the Shoemaker-Levy im­pacts,” said as­tron­o­mer James Gra­ham, al­so of Berke­ley, who helped with the new ob­serva­t­ions as well as with ob­serva­t­ions tak­en dur­ing the Shoe­ma­ker-Levy 9 event.

Mike Wong, a Berke­ley re­search­er cur­rently on leave at the Space Tel­e­scope Sci­ence In­sti­tute in Bal­ti­more, used the ob­serva­t­ions to cal­cu­late that the scar is near the south­ern pole of Ju­pi­ter and 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 frag­ment­ed the im­pactor shortly be­fore it col­lid­ed with the plan­et, re­search­ers said.

The im­pact fell on the 15th an­ni­ver­sa­ry of the Shoe­ma­ker-Levy 9 im­pacts, but the co­in­ci­dences do not end the­re. Kalas’ or­i­ginal plan was to search for a pre­vi­ously de­tected Ju­pi­ter-like plan­et around the star Fo­mal­haut. The star is lo­cat­ed roughly 25 light years from Earth in the di­rec­tion of the con­stella­t­ion Pis­cis Aus­tri­nus. Kalas found pre­vi­ously that the plan­et, dubbed Fo­mal­haut b, is bright, and one ex­plana­t­ion for that bright­ness is that it is suf­fer­ing im­pacts just like Ju­pi­ter, he said.

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Something slammed into Jupiter in the last few days, creating a dark bruise about the size of the Pacific Ocean, atronomers say. The bruise was noticed by an amateur astronomer on July 19. University of California at 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 the next day. The image in near-infrared light showed a bright spot in the southern hemisphere, a sign of reflective particles floating high in Jupiter’s sky. In visible light, the bruise appears dark against the bright surface of Jupiter. “This was most likely the result of a single asteroid,” said astronomer Frank Marchis at Berkeley. The Keck observation marks only the second time astronomers have seen the results of an impact on the planet. The first occurred 15 years ago, between July 16 and 22, 1994, when more than 20 fragments of comet Shoemaker-Levy 9 collided with Jupiter. The Shoemaker-Levy 9 impact events were well-studied by astronomers, and many theories were subsequently developed based on the observations. “Now we have a chance to test these ideas on a brand new impact,” said Kalas, who with colleagues watched the aftermath of the new 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.” “The fact that [the feature] shows up so clearly means that it’s associated with high-altitude aerosols, as seen in the Shoemaker-Levy impacts,” said astronomer James Graham, also of Berkeley, who helped with the new observations as well as with observations taken during the SL9 event. Mike Wong, a Berkeley researcher currently on leave at the Space Telescope Science Institute in Baltimore, used the observations to calculate that the scar is near the southern pole of Jupiter and 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 fragmented the impactor shortly before it collided with the planet, researchers said. The impact fell on the 15th anniversary of the SL9 impacts, but the coincidences do not end there. Kalas’ original plan was to search for a previously detected Jupiter-like planet around the star Fomalhaut. The star is located roughly 25 light years from Earth in the direction of the constellation Piscis Austrinus. Kalas showed previously that the planet, dubbed Fomalhaut b, is bright, and one explanation for that brightness is that it is suffering impacts just like Jupiter, he said. Later this week, astronomers from 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. But the Keck images reported here will provide a crucial baseline for measuring the spread of impact-related material, Wong said. No other method exists to directly track the winds at these rarified levels of Jupiter’s atmosphere.