Discovering Pluto's Atmosphere

Observations of the occultation of an obscure 12th-magnitude star in eastern Virgo by Pluto on June 9, 1988 are discussed. The occultation was observed by astronomers aboard NASA's Kuiper Airborne Observatory flying over the Pacific. The prediction of the occultation and the results of the observations are examined. The study demonstrated that Pluto has a thin atmosphere and that its diameter is about two-thirds that of the moon.