Free Astronomy Magazine November-December 2016

SPACE CHRONICLES out warning, and so we don't have much chance to get useful data. With Hubble's fantastic resolution, not only do we see really tiny, faint bits of the comet, but we can watch them change from day to day. And that has allowed us to make the best measurements ever obtained on such an object.” The three-day observations reveal that the comet shards brighten and dim as icy patches on their surfaces rotate into and out of sunlight. Their shapes change, too, as they break apart. The icy relics comprise about 4 percent of the parent com- et and range in size from roughly 65 feet wide to 200 feet wide. They are moving away from each other at a few miles per hour. The Hubble images show that the parent comet also changes bright- ness cyclically, completing a rotation every two to four hours. A visitor to the comet would see the Sun rise and set in as little as an hour. The comet is also much smaller than as- tronomers thought, measuring only 1,600 feet across, about the length of five football fields. Comet 332P was discovered in November 2010, after it surged in brightness and was spotted by two Japanese amateur astronomers, Kaoru Ikeya and Shigeki Murakami. Based on the Hubble data, the re- search team suggests that sunlight heated up the comet, causing jets of gas and dust to erupt from its surface. Because the nucleus is so small, these jets act like rocket en- gines, spinning up the comet's rota- tion. The faster spin rate loosened chunks of material, which are drift- ing off into space. The research team calculated that the comet probably shed material over several months, between Oc- tober and December 2015. Jewitt suggests that even some of the ejected pieces have themselves fal- len to bits in a kind of cascading fragmentation. “Our analysis shows that the smaller fragments are not as abundant as one might expect based on the number of bigger chunks,” he said. “This is suggestive that they're being depleted even in the few months since they were launched from the primary body. We think these little guys have a short lifetime.” Hubble's sharp vision also spied a chunk of material close to the comet, which may be the first salvo of an- other outburst. The remnant from still another flare-up, which may have occurred in 2012, is also visible. The fragment may be as large as Comet 332P, suggesting the comet split in two. But the icy remnant wasn't spotted until Dec. 31, 2015, by the Pan-STARRS (Panoramic Survey Telescope and Rapid Response Sys- tem) telescope in Hawaii, in work supported by the Near-Earth Object Hubble takes close-up look at disintegrating comet by NASA N ASA's Hubble Space Telescope has captured one of the sharp- est, most detailed observa- tions of a comet breaking apart, which occurred 67 million miles from Earth. In a series of images taken over a three-day span in January 2016, Hubble revealed 25 building- size blocks made of a mixture of ice and dust that are drifting away from the comet at a leisurely pace, about the walking speed of an adult. The observations suggest that the roughly 4.5-billion-year-old com- et, named 332P/Ikeya-Murakami, or Comet 332P, may be spinning so fast that material is ejected from its surface. The resulting debris is now scattered along a 3,000-mile-long trail. These observations provide insight into the volatile behavior of comets as they approach the sun and begin to vaporize, unleashing dynamical forces. Comet 332P was 150 million miles from the Sun, slightly beyond the orbit of Mars, when Hubble spotted the breakup. “We know that comets sometimes disintegrate, but we don't know much about why or how they come apart,” explained lead researcher David Jewitt of the University of Cal- ifornia at Los Angeles. “The trouble is that it happens quickly and with-