Rosetta captures images of jet-blasting comet
时间：2019-10-08 责任编辑：眭趿狒 来源：澳门赌博网址大全-2019专业平台Welcome√ 点击：299 次
Cameras on the spacecraft captured powerful jets of steam and dust erupting from as it tore past the sun on . Images beamed back from the probe showed the comet spewing material as it warmed up on its closest pass of the sun and began its journey back out into the frigid far reaches of the solar system.
Pictures taken a few hours before the comet’s close encounter with the sun recorded one powerful outburst that flung a visible, bright, stream of dust and vapour several kilometres into space.
, the lead scientist on Rosetta’s Osiris camera, compared the jet blasting from the spinning comet to a garden water sprinkler. “It’s the first time this has been seen in space,” he said.
When Rosetta, which was built and launched by the , arrived at the comet in August last year its surface temperature was a chilly -70C (-94F). But as the comet swung closer to the sun, its surface warmed. In May, the comet was a few degrees below 0C (32F). Over the next month, it could reach 30C.
The rise in temperature has transformed the comet from a dull and frozen lump into a body billowing furiously as it tumbles through space. The amount of water being shed from the comet has risen 1,000-fold in the past year. The comet now sheds 300kg of water every second, enough to fill an Olympic swimming pool every two-and-a-half hours. The vapour leaving the comet dislodges a tonne of dust every second.
Other images released by the Rosetta team on Thursday showed a boulder being blasted off the surface of the comet and out into space. Sierks said the boulder was spinning at five revolutions a second and going fast enough to leave the comet, which has a length of about 4km (2.4 miles) for good rather than go into orbit around it. Mission scientists are still calculating the size of the boulder, but said it was between four metres and 40 metres wide.
Much of the gas and debris dislodged from the surface forms the comet’s atmosphere or coma, or helps to build up its spectacular tail. Rosetta is too close to image the comet’s tail directly, but groundbased telescopes have measured it stretching out across 120,000km (74,564 miles).
Rosetta orients itself by the stars and has had to back away from the comet to prevent its star trackers from being blinded by dust. The latest images were taken at about 330km away from the comet. At such a distance Rosetta’s cameras cannot see whether a 500-metre crack in the neck of the comet has widened. At some point the comet could break in two, but the chances of that happening while Rosetta is orbiting the comet were minuscule, said Sierks.
Down on the surface the conditions are becoming ever more violent for the little Philae lander, which, in November last year, became the on a comet. The ESA lander has in the past month, but scientists hope it may still make contact now that it is receiving more sunlight to charge its batteries and Rosetta has flown back up to the comet’s north where communcation links are easier.
, Philae operations engineer, said the powerful vapour jets were unlikely to knock Philae off the comet but might push it into a bad position where it could not call home. “There’s a danger that it might change the attitude of Philae,” she said. The team is now working on a way to send commands to Philae in the hope of getting fresh data back from the battered lander.
Rosetta will escort the comet out towards Jupiter until September 2016 when flight controllers will fly lower and lower around the comet until the spacecraft crash lands.
“I’d bet on a hardish landing,” said , spacecraft operations engineer. “There are boulders and mountain-sized rocks everywhere. It’s very likely the spacecraft will hit one of those and stumble at the end. So it will not be very graceful.”