Ganymede may have an aurora of its own.Auroras aren't just for planets anymore. Typically generated when a magnetic field sends charged particles crashing into a planet's atmosphere, the shimmering lights of an aurora grace the north and south polar skies of Earth, Jupiter, Saturn, Uranus, and Neptune. It now seems that Jupiter's moon Ganymede joins the ranks of the big guys. Ultraviolet emissions recorded by the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. suggest that this satellite has its own polar light show. If the finding is confirmed, Ganymede would be the first moon known to possess an aurora. Hubble has tracked Jupiter and its moons for over a year, first as a scout for the Galileo spacecraft, then as an occasional collaborator during the craft's 2-year Jovian tour, which began last December. In June, just before Galileo's first rendezvous with Ganymede, Hubble's Goddard high- resolution spectrograph measured ultraviolet light emitted by the moon. The spectra revealed that Ganymede, like the Jovian moon Europa, has a thin atmosphere rich in oxygen. Ganymede's spectra show two distinct peaks caused by oxygen, indicating that such emissions do not arise uniformly throughout the moon's atmosphere. Judging from the orientation of Ganymede as it passed across the aperture of the spectrograph, Doyle T. Hall of Johns Hopkins University Johns Hopkins University, mainly at Baltimore, Md. Johns Hopkins in 1867 had a group of his associates incorporated as the trustees of a university and a hospital, endowing each with $3.5 million. Daniel C. in Baltimore and his colleagues find that the peaks come from Ganymede's north and south poles North and South Poles figurative ends of the earth. [Geography: Misc.] See : Remoteness . That pattern is just what an aurora would produce, says study collaborator Melissa McGrath of the Space Telescope Science Institute The Space Telescope Science Institute (STScI) is the science operations center for the Hubble Space Telescope (HST; in orbit since 1990) and for the James Webb Space Telescope (JWST; scheduled to be launched in 2013). in Baltimore. She reported the details last week at a workshop on the Goddard spectrograph at NASA's Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. The findings are all the more intriguing, notes Hall, because during its June rendezvous, Galileo found evidence that Ganymede has its own magnetic field and charged particles nearby-prerequisites for generating an aurora (SN: 7/20/96, p. 37). A Sept. 6 flyby fly·by also fly-by n. pl. fly·bys A flight passing close to a specified target or position, especially a maneuver in which a spacecraft or satellite passes sufficiently close to a body to make detailed observations without has now confirmed the magnetic field, says Margaret G. Kivelson of the University of California, Los Angeles UCLA comprises the College of Letters and Science (the primary undergraduate college), seven professional schools, and five professional Health Science schools. Since 2001, UCLA has enrolled over 33,000 total students, and that number is steadily rising. . Ganymede lies within the vast region dominated by Jupiter's huge magnetic field. Jupiter may supply the charged particles needed to create Ganymede's aurora, says John T. Clarke of the University of Michigan (body, education) University of Michigan - A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries. in Ann Arbor, much as the sun's wind supplies the charged particles that generate Earth's auroras. Astronauts are scheduled to replace Hubble's spectrographs next February with a device that can simultaneously record images and spectra. If Ganymede has an aurora, this device should detect it directly, McGrath says. |
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