Sizing up Pluto's moon.Pluto's moon Charon recently took a trip on the dark side. On July 10, 2005, the moon passed in front of a star, briefly blocking the star's light. This brief blockage, however, was long enough to give astronomers new information about Pluto's rocky partner. Passing in front of a star is a rare event for Charon. The trip lasted less than a minute, and it was visible only from a 980-kilometer (609-mile) stretch of land in South America South America, fourth largest continent (1991 est. pop. 299,150,000), c.6,880,000 sq mi (17,819,000 sq km), the southern of the two continents of the Western Hemisphere. . The passage of one celestial body in front of another is known as an occultation occultation (ŏk'əltā`shən), in astronomy, eclipse of one celestial body by another, e.g., when the moon lies between a star and the earth. Occultations of stars by the moon are important in astronomy. . Two teams of astronomers watched the event through telescopes in Chile and Brazil. One team works at the Massachusetts Institute of Technology Massachusetts Institute of Technology, at Cambridge; coeducational; chartered 1861, opened 1865 in Boston, moved 1916. It has long been recognized as an outstanding technological institute and its Sloan School of Management has notable programs in business, and Williams College Williams College, at Williamstown, Mass.; coeducational; chartered 1785, opened as a free school 1791, became a college 1793, named for Ephraim Williams. The Williams campus, noted for its fine old buildings, includes West College (1790), the Van Rensselaer Manor . The other is from the Paris Observatory. The observations show that Charon has a radius of 606 kilometers (377 miles). In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , it measures about 754 miles across. This new size estimate, combined with data obtained 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. , indicates that the moon is 1.71 times as dense as water. Earth's density is about three times that of Charon, suggesting that, unlike Earth, Charon is largely made up of rock and ice. The scientists couldn't tell for sure whether Charon has an atmosphere. If there is one, however, it's less than one-millionth as dense as Earth's atmosphere is. The new data support the theory that Charon formed when a big object collided with Pluto and flung off a chunk. Earth's moon probably formed in the same way. http://www.sciencenewsforkids.org/articles/20060222/Note3.asp |
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