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How was Pluto’s atmosphere discovered in 1988?
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Pluto
Pluto as observed by the New Horizons spacecraft, July 13, 2015.
Pluto’s atmosphere was discovered in 1988 when the dwarf planet passed in front of, or occulted, a star as observed from Earth.1
During this event, astronomers observed that the star’s light gradually dimmed just before it disappeared behind Pluto. This specific change in brightness demonstrated the presence of a thin, greatly distended atmosphere surrounding the body. This method of using stellar occultations is a standard technique in astronomy for gathering data on planetary atmospheres, as the way a star's light is obscured can reveal the density and composition of the gases through which it passes.12