Free Astronomy Magazine November-December 2016

SPACE CHRONICLES Observations program in NASA's Planetary Defense Coordination Office. That discovery prompted Jewitt and colleagues to request Hubble time to look at the comet in detail. Around the same time, astronomers around the world began to notice a cloudy patch of material near the com- et, which Hubble later resolved into the 25 pieces. “In the past, astrono- mers thought that com- ets die when they are warmed by sunlight, causing their ices to simply vaporize away,” Jewitt said. “Either nothing would be left over or there would be a dead hulk of material where an active comet used to be. But it's starting to look like fragmentation may be more impor- tant. In Comet 332P we may be seeing a comet fragmenting itself into oblivion.” “Hubble's best previous glimpse at a fragment- ing comet came during Advanced Camera for Surveys (ACS) observa- tions of 73P/Schwass- mann-Wachmann 3 (73P) in April 2006,” said collaborator Har- old Weaver of the Johns Hopkins Univer- sity Applied Physics Laboratory in Laurel, Maryland. “In those ob- servations, Hubble wit- nessed a comet with more than 60 named pieces. The Hubble im- ages showed unprece- dented detail of 73P's breakup, but the comet wasn't observed long enough to document the evolution of the fragments over time, unlike the case of 332P.” The researchers esti- mate that Comet 332P contains enough mass to endure another 25 outbursts. “If the comet has an episode every six years, the equivalent of one orbit around the Sun, then it will be gone in 150 years,” Jewitt said. “It's the blink of an eye, astronomically speaking. The trip to the inner solar system has doomed it.” The icy visitor hails from the Kuiper Belt, a vast swarm of objects at the outskirts of our solar system. These icy relics are the leftover build- ing blocks from our solar system's construc- tion. After nearly 4.5 billion years in this icy deep freeze, chaotic gravitational pertur- bations from Neptune kicked Comet 332P out of the Kuiper Belt. As the comet traveled across the solar system, it was deflected by the planets, like a ball bouncing around in a pinball machine, until Jupiter's gravity set its current orbit. Jewitt estimates that a comet from the Kuiper Belt gets tossed into the inner solar system every 40 to 100 years. T his NASA Hubble Space Telescope image reveals the ancient Comet 332P/Ikeya-Murakami disintegrating as it approaches the sun. The observations represent one of the sharpest views of an icy comet breaking apart. The comet debris consists of a cluster of building-size chunks near the center of the image. They form a 3,000-mile-long trail, larger than the width of the continental U.S. The fragments are drifting away from the comet, dubbed Comet 332P, at a leisurely pace, roughly the walking speed of an adult. The main nucleus of Comet 332P is the bright object at lower left. It measures 1,600 feet across, about the length of five football fields. Hubble spied the debris on Jan. 26, 27, and 28, 2016, when the comet was 150 million miles from the sun, slightly beyond the orbit of Mars. The 4.5-billion-year-old comet, which originated from the Kuiper Belt, probably shed the debris over a short period of time, from October to December 2015. The comet shards brigh-ten and dim as icy patches on their surfaces rotate into and out of sunlight. The icy relics, totaling about 25 pieces, comprise about 4 percent of the comet and range in size from roughly 65 feet wide to 200 feet wide. The tiny white dot just above the comet may be an- other fragment, signaling the beginning of another outburst. These observations provide insight into the volatile behavior of comets as they approach the sun and begin to vaporize, unleashing dynamical forces. Theimage was taken on Jan. 27, 2016, with Hub- ble's Wide Field Camera 3. [NASA, ESA, and D. Jewitt (UCLA)] n