Scientists have been surprised by unexpected changes in the temperature of Neptune.
Researchers found that the planet’s temperature dropped in a way they did not forecast – and then dramatically warmed at the south pole.
The researchers made the discovery after tracking the planet’s temperature changes over 17 years.
“This change was unexpected,” said Michael Roman, lead author on the new study, in a statement. “Since we have been observing Neptune during its early southern summer, we expected temperatures to be slowly growing warmer, not colder.”
The variations were so shocking that researchers are not yet able to explain them. They coulddbe the result of chemistry on the planet, weather patterns, or changes in the Sun – and researchers hope to answer that question and more with future observations.
“I think Neptune is itself very intriguing to many of us because we still know so little about it,” said Dr Roman. “This all points towards a more complicated picture of Neptune’s atmosphere and how it changes with time.”
Neptune goes through seasons, just like Earth does, as it moves around the Sun. But a Neptune season is much longer, at about 40 years, since a whole Neptune year takes 165 Earth years.
That meant that scientists were keen to understand how those long seasonal changes might happen, especially in the wake of the summer solstice on the south of Neptune. To track them, scientists looked at almost 100 thermal-infrared images of the planet.
They found that even though summer had arrived, most of the planet had actually cooled. But then the south pole started warming again.
Between 2003 and 2018, the average temperature across the planet dropped by 8C. Then, at the south pole, it rose 11C between 2018 and 2020.
Neither of those rapid changes were expected by scientists. The period covered is less than one season, and so scientists had expected far more gradual variations.
The research is described in a new paper, ‘Sub-Seasonal Variation in Neptune’s Mid-Infrared Emission’, published in The Planetary Science Journal today.