The most distant planet in our solar system has presented a new mystery, scientists told CNN.
Astronomers who have been observing Neptune over the past 17 years with several ground-based telescopes have tracked the ice giant’s unexpected drop in global temperature, followed by a sharp warming trend at the planet’s south pole.
Neptune, which orbits the Sun at a distance of 2.8 billion miles (4.5 billion kilometers), experiences seasons just like the Earth, only they last much longer. One year on Neptune lasts about 165 Earth years, so one season can last about 40 years. Since 2005, it has been summer in Neptune’s southern hemisphere.
Astronomers decided to track the temperature of the planet’s atmosphere after the southern summer solstice occurred this year.
Nearly 100 thermal images of Neptune taken since then have shown that much of Neptune has gradually cooled, falling by 8 degrees Celsius between 2003 and 2018.
A study of this phenomenon has been published in the Planetary Science Journal.
“This change was unexpected,” study lead author Michael Roman, a research fellow at the University of Leicester, said in a statement. “Because we observed Neptune at the beginning of the austral summer, we expected the temperature to slowly rise rather than fall.”
Then, between 2018 and 2020, there was a sharp warming at Neptune’s south pole, with temperatures rising by 11 degrees Celsius. This warm polar vortex has completely reversed any cooling that was previously occurring.
Such a polar warming has not yet been observed on Neptune.