Rosetta Records Temperature, Observes Coma As It Nears Comet 67P b4in.org/f6Mc After a journey of more than six billion kilometers through the Solar System, the ESA’s Rosetta probe is closing in on comet 67P/Churyumov–Gerasimenko (67P), and with less than a week to go until its arrival, it recently managed to take the comet’s temperature for the first time and has captured images of a coma surrounding its nucleus. Rosetta, which lifted off from a European spaceport in French Guiana in March 2004, has already journeyed around the Sun five times, picking up speed through a series of gravity-assisted swingbys around Earth and Mars in order to achieve an orbit similar to 67P’s. Its goal, the agency said, is to match the 55,000 km/h pace of the comet and travel alongside it. Since early May, the probe’s controllers have been running it through a series of planned maneuvers designed to reduce its speed with respect to the comet by approximately 2800 km/h in order to ensure it arrives by August 6. In the meantime, however, Rosetta has been able to use its instruments to conduct a series of observations and measurements of its target, allowing astronomers to learn more about the unusual, rubber-duck shaped comet. Using its infrared and thermal imaging spectrometer (VIRTIS), Rosetta conducted a series of observations from between July 13 and July 21. Those observations, which came when the comet was roughly 555 km away from the Sun, revealed that the average surface temperature of 67P was approximately -70 degrees Celsius – up to 30 degrees warmer than predicted for an ice-covered comet at that distance, according to the ESA. “This result is very interesting, since it gives us the first clues on the composition and physical properties of the comet’s surface,” VIRTIS principal investigator Dr. Fabrizio Capaccioni said in a statement Friday. He explained that the temperature measurements confirm most of the comet’s surface will be dusty, because darker material warms and emits heat more readily than ice when exposed to sunlight. The findings do not “exclude the presence of patches of relatively clean ice, however,” he added, “and very soon, VIRTIS will be able to start generating maps showing the temperature of individual features.” In addition, images taken by Rosetta’s onboard scientific imaging system OSIRIS on July 25 clearly show signs of an extended coma surrounding the nucleus of 67P, according to NASA. The image covers an area of 150 by 150 square kilometers, said Luisa Lara from the Institute of Astrophysics in Andalusia, Spain, but scientists believe that it is actually much larger than that. According to the ESA, OSIRIS previously detected a distinct rise in the comet’s activity which revealed a coma that spanned more than 1,000 km. While that activity ultimately died down, the new image confirms an extended coma close to the nucleus of 67P, where the particle densities are at their highest. They, too, predict that it extends much further into its surroundings. More b4in.org/f6Mc
Posted on: Sun, 03 Aug 2014 15:56:21 +0000
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