Distant dwarf planet gives up its secrets

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GRANADA, Spain, Nov. 21 (UPI) -- European astronomers say they've taken advantage of a cosmic opportunity to learn more about the icy dwarf planet Makemake, thought to be similar to Pluto.

Makemake's rare passage in front of a background star has yielded new information about its size, shape and surface properties, the researchers report in Nature.

Pluto, demoted to the status of dwarf planet, is one of at least four known dwarfs orbiting the sun. Makemake, (pronounced MAH-kay MAH-kay,) which orbits farther from the sun than Pluto, has been found to have no atmosphere, unlike Pluto, which has a thin but detectable atmosphere.

Jose Ortiz of the Instituto de Astrofísica de Andalucia in Spain and colleagues studied Makemake using the same technique used to probe an even more distant dwarf planet, Eris, a year ago.

"Pluto, Eris and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our sun," Ortiz said.

By studying the change in light of a distant star as Makemake passed directly in front of it, the astronomers said they were able to determine the dwarf planet's size and surface brightness, results that rule out a global, Pluto-like atmosphere.

"As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually," Ortiz said. "This means that the little dwarf planet has no significant atmosphere."