A warmer, fluffier Pluto
By Ron Cowen
Because Pluto has been receding from the sun for more than a decade, planetary scientists presumed that its temperature had dropped and its nitrogen atmosphere had shrunk. But between 1988 and 2002, Pluto’s atmosphere nearly doubled in size and its temperature increased by about 1C, report James L. Elliot of the Massachusetts Institute of Technology and his colleagues in the July 10 Nature. Another team, led by Bruno Sicardy of the Observatory of Paris, reports in the same journal that Pluto’s atmospheric pressure doubled during that 14-year interval.
The researchers observed Pluto on Aug. 20, 2002, when the planet passed in front of a bright star (SN: 9/7/02, p. 148: Available to subscribers at Pluto and the Occult: Rare events illuminate Pluto’s atmosphere). Several large telescopes recorded the starlight filtering through Pluto’s tenuous atmosphere, revealing the atmosphere’s pressure, temperature, and height. The scientists then compared their measurements with those made in 1988, when Pluto eclipsed another star.