Astronomers use India’s largest optical telescope to peer into Pluto and reveal hidden mysteries

More than 16 years after being downgraded from a full-time planet to a dwarf, Pluto still remains the center of attraction for astronomers around the world. An international team of astronomers, including from India, have now derived the precise value of Pluto’s atmospheric pressure on its surface.

The atmospheric pressure on Pluto is 80,000 times lower than atmospheric pressure at mean sea level on Earth. The pressure was calculated by observing a stellar occultation by Pluto in June 2020 using a 3.6m Devasthal Optical Telescope (DOT) (India’s largest optical telescope) and 1.3m Devasthal Fast Optical Telescope (DFOT) telescopes located in Devasthal, Nainital.

The team included scientists from the Aryabhatta Research Institute of Observational Sciences (ARIES), who used signal-to-noise ratio light curves obtained from the sophisticated instruments used in the observations to derive an accurate value for atmospheric pressure from Pluto on its surface.

Credits: NASA


The astronomers used data gathered from 12 occultations, which occur when a celestial object is hidden from view by the observer due to another celestial object passing between them. These 11 events took place between 1988 and 2016, which showed a monotonous triple increase in pressure over this period.

Research published in Astrophysical Journal Letters showed that since mid-2015 Pluto’s atmosphere has been in a plateau phase, close to a peak. The team further explained that this occultation is particularly timely because it can test the validity of current models of the evolution of Pluto’s atmosphere.

“This increase can be consistently explained by a volatile transport model of Pluto, which predicts the pressure to peak around 2020. A gradual decline is then expected to last two centuries under the combined effects of Pluto’s recession relative to the Sun. and the prevalence of the winter season on Sputnik Planitia,” the newspaper said.

Photo: Ministry of Science and Technology


The new observations also confirmed that the planet is suffering from intense seasonal episodes due to a great depression known as Sputnik Planitia. Meanwhile, its poles remain, for decades, in permanent sunlight or darkness during its 248-year orbital period. This leads to strong effects on its nitrogen (N2) atmosphere which is mainly controlled by the vapor pressure equilibrium with the surface N2 ice.

The Nasa New Horizons flyby in July 2015 revealed Sputnik Planitia, filled with N2 ice, which appears to be the primary driver controlling the seasonal variation in atmospheric pressure over a seasonal cycle

The researchers observed that Pluto is now moving away from the galactic plane as seen from Earth and that stellar occultations by the dwarf planet are becoming increasingly rare, making this event a watershed event.

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