An international team of astronomers have used ground-based telescopes, including the European Southern Observatory’s Very Large Telescope (ESO’s VLT), to track Neptune’s atmospheric temperatures over a 17-year period. They found a surprising drop in Neptune’s global temperatures followed by dramatic warming at its south pole.
“This change was unexpected,” says Michael Roman, a postdoctoral research associate at the University of Leicester, UK, and lead author of the study published today in The Planetary Science Journal. “Since we have been observing Neptune during its early southern summer, we expected temperatures to be slowly growing warmer, not colder.”
Like Earth, Neptune experiences seasons as it orbits the Sun. However, a Neptune season lasts around 40 years, with one Neptune year lasting 165 Earth years. It has been summertime in Neptune’s southern hemisphere since 2005, and the astronomers were eager to see how temperatures were changing following the southern summer solstice.
Astronomers looked at nearly 100 thermal-infrared images of Neptune, captured over a 17-year period, to piece together overall trends in the planet’s temperature in greater detail than ever before.