An international group of scientists used infrared observations to track temperature changes on Neptune over the course of 17 years. First, there has been a drop in global temperature, and in recent years, the temperature has increased abruptly at the planet’s south pole, the European Southern Observatory (ESO) reports.

Neptune is the last planet in the solar system at a distance from the sun. Like the earth, witness the seasons. One year on Neptune is 165 Earth years. The seasons are also longer – they last about 40 Earth years.

It’s been summer in Neptune’s southern hemisphere since 2005. Astronomers wanted to know how temperatures changed after the summer solstice, and to do so they analyzed 100 infrared images of the planet acquired over a 17-year period.

The results turned out to be surprising. Although summer has arrived in the Southern Hemisphere, a large part of the planet has gradually cooled down over two decades. Between 2003 and 2018, the average global temperature fell by 8°C.

The publication’s first author, Michael Roman from the University of Leicester in the UK, noted that the change was unexpected for scientists as they were observing Neptune during the early Southern Hemisphere summer, so they expected gradual, cooler temperatures. noticeably instead.

However, this is not the end of the surprises. During the last years of observations, the temperature of the southern hemisphere has improved significantly, by as much as 11 °C (from 2018 to 2020). The warm polar vortex of Neptune was known before, but such a sharp warming was never observed in the polar region of the planet.

“Our data covers less than half of the season on Neptune, so no one expected to see big, rapid changes,” explains Glenn Orton of the Jet Propulsion Laboratory (JPL) in the US, who was involved in the study.

The telescope’s cameras recorded mid-infrared radiation emitted from Neptune’s atmosphere, known as the stratosphere. Scientists collected all available data from ground-based telescopes from 2003 to 2020. These were the European Southern Observatory’s VLT telescope, the Gemini South telescope (both in Chile), and the Subaru, Keck and Gemini North telescopes (all in Hawaii). In addition, data from the Spitzer Space Telescope was used.

Fluctuations in temperature can be caused by changes in Neptune’s stratospheric chemistry, random weather events, or the solar cycle, but the exact cause is unknown. Scientists hope that the recently launched James Webb Space Telescope (owned by NASA, the European Space Agency, and the Canadian Space Agency), the Very Large Ground Telescope (currently being built by ESO) and other new telescopes will provide better observations and help unravel the mystery of changes temperature on Neptune.

The results of the research were published in the scientific journal “The Planetary Science Journal”. (PAP)