It is a world wrapped in mystery – the seventh planet from the Sun, Uranus, seen up close just once nearly four decades ago by a passing NASA probe and still warily guarding its secrets. But new telescopic observations from a telescope located in New Mexico provide astronomers with a fuller understanding of the planet’s atmosphere, including detecting a polar cyclone whose center measures a quarter of Earth’s diameter, swirling near its north pole. Scientists published their findings in the journal Geophysical Research Letters.
Astronomers think that, like on Earth, water and methane lie beneath Uranus’s hydrogen and helium atmosphere and that these materials merge in a slushy transition zone that surrounds a dense rocky core. Using the Very Large Array — a series of radio antenna dishes that act as one giant telescope — scientists found that air in the northern hemisphere at Uranus’s north pole is warmer and drier than elsewhere. This is a sign of an intense cyclone.
Last year’s study also showed that the icy giant’s weather isn’t as inert as once thought, with active storms that can be powerful. But this new polar vortex is even more intriguing because it’s the first time seen on Uranus. After all, the planet passed through its northern spring, and its north pole was facing the Sun.
Unlike Neptune, Uranus’s rotational axis does not point directly at the Sun, resulting in a much lighter atmosphere with fewer dynamic features. But it rotates on its side, meaning its polar regions see seasons.
The south-polar region of Uranus is visible this summer and has been brightened by the Sun. The Webb telescope is studying it now to understand its properties. “Webb will help us see how the cap appears when the solar rays hit it and disappear in the autumn,” said a planetary scientist at NASA’s Jet Propulsion Laboratory in California.
The polar cap is a distinct feature of Uranus, which has a ring system and five significant moons that all appear to have been formed recently. The planet also has an unusually high proportion of methane to hydrogen in its atmosphere, giving it a greenish color that distinguishes it from other ice giants like Neptune. These quirks are part of why planetary scientists have been pushing for a dedicated mission to Uranus and perhaps Neptune in 2028. It would provide a rare opportunity to learn more about these fascinating worlds and how they form. But they’ll need a few more data sets to make that happen. This includes an orbital trajectory allowing the mission to visit these enigmatic worlds while their rings remain intact. That’s essential in figuring out how the solar system came to have these weird quirks.