Neptune is in the midst of a mystery. 17 years’ worth of observations has been analyzed, including data from the Gemini South and North telescopes, the Subaru telescope, the Keck Telescope, and the European Southern Observatory’s Very Large Telescope. They’ve also discovered unexpected temperature fluctuations on the planet, which they haven’t been able to explain.
As Neptune rotates and revolves around the sun, it experiences seasons. However, its seasons last roughly 40 years, compared to Earth’s annual cycle of 365 days. It’s been summer in the southern hemisphere since 2005, thus experts were astonished to see such a large temperature difference between 2005 and 2013.
Co-author Glenn Orton, the senior research scientist at NASA’s Jet Propulsion Laboratory, remarked, “Our data span less than half of a Neptune season, so no one was expecting to find big and rapid changes.”
A series of measurements taken between 2003 and 2018 found that the global average temperature of the planet dropped by eight degrees Celsius (46 degrees Fahrenheit), and then between 2018 and 2020, the temperatures around the planet’s southern pole rose quickly by 11 degrees Celsius (52 degrees Fahrenheit). In spite of this, Neptune’s southern pole has a vortex, or area of atmospheric turbulence, which has a direct impact on the planet’s southern temperatures. However, this is not enough to explain how temperatures soared so quickly. In addition, the worldwide cooling trend is puzzling.
The study’s principal author, Michael Roman of the University of Leicester in the United Kingdom, said, “This development was unanticipated.” Temperatures on Neptune have been steadily rising since scientists began viewing the planet in its southern summer months.
It’s not obvious what prompted the astronomers’ results, and they don’t know how to explain it. According to the European Southern Observatory, the planet’s temperature fluctuations could be the result of a weather event, changes in atmospheric chemistry, or even solar-induced impacts.
More observations of Neptune will be necessary with future strong telescopes like the Extremely Large Telescope and the James Webb Space Telescope in order to learn more.
Many people are fascinated by Neptune since we know so little about it, Roman explains. A more complex picture of Neptune’s atmosphere and how it changes over time may be drawn from these data.
In the journal The Planetary Science Journal, the findings have just been published.