Something strange has happened to the temperature of Neptune that has left scientists scratching their heads.
The enormous ice planet known for its deep blue colour has had its temperature tracked over the course of 17 years, and after analysing thermal infrared images, researchers have discovered that the temperature has been fluctuating with a period of cooling followed by a dramatic warming of its south pole.
There was a drop in temperature by 8°C in the years 2003-2009, but the temperatures later rose by 11°C in the south pole from 2018-2020, scientists were surprised at these changes - it could even be said they quite literally came out of the blue.
"Since we have been observing Neptune during its early southern summer, we expected temperatures to be slowly growing warmer, not colder," he said.
Neptune has an axial tilt like Earth, meaning it experiences seasons - albeit they are much longer than ours, due to how far away it is.
While it takes the planet 165 Earth years to orbit around the sun, a full season on Neptune is 40 years - so the 17 years of studies are equivalent to less than half of a season which is why scientists thought the seasons change slowly.
Dr Glenn Orton, Senior Research Scientist at JPL and co-author of the study, referred to this point: "Our data cover less than half of a Neptune season, so no one was expecting to see large and rapid changes."
As the reason behind the temperature change remains unproven, scientists think it may be due to changes in the sun, weather patterns or Neptune's chemistry and hope to find this out with further research.
"Temperature variations may be related to seasonal changes in Neptune's atmospheric chemistry, which can alter how effectively the atmosphere cools, but random variability in weather patterns or even a response to the 11-year solar activity cycle may also have an effect."