When Pluto crossed in front of a star on August 15, 2018, a team of astronomers led by the Southwest Research Institute set up telescopes across the United States and Mexico to view Pluto's atmosphere when it was briefly illuminated by the well-placed light. Scientists analyzed the occultation event to determine the overall abundance of Pluto's fragile atmosphere, and discovered persuasive evidence that it is beginning to vanish, refreezing back onto the surface as the planet moves further away from the Sun.
"The ongoing existence of Pluto's atmosphere shows that stored heat underneath the surface kept nitrogen ice reservoirs on Pluto's surface warm. They're starting to cool, according to new data "Dr. Leslie Young, a staff scientist at SwRI, agreed. During the occultation, the star faded from view as Pluto's atmosphere and solid body passed in front of it, which took around two minutes. The density profile of Pluto's atmosphere was determined from the pace at which the star vanished and returned.