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| Hubble Space Telescope images chronicling the waxing and waning of the cloud cover on Neptune. NASA, ESA, Erandi Chavez (UC Berkeley), Imke de Pater (UC Berkeley) |
Neptune, the eighth planet in our solar system, used to have eerie clouds, but they've now disappeared. Astronomers are puzzled by this change. Scientists believe there's a connection between the sun's cycles and Neptune's atmosphere.
Each planet in our solar system looks different. Earth has blue oceans, Jupiter has storms, Saturn has rings, and Neptune had ghostly clouds. But for the first time in 30 years, Neptune's clouds are almost gone, which is surprising to astronomers.
Neptune's clouds have changed over time. Since October 2019, there's been only one small patch of clouds near its south pole. This is unusual, and scientists are trying to figure out why.
To solve the mystery, researchers looked at 30 years of pictures of Neptune taken by telescopes like Hubble and observatories on Earth. They published a study in the journal Icarus in June, where they named the main reason for the disappearing clouds: the sun.
Neptune is a cold planet with powerful storms, and we've only sent one spacecraft, Voyager 2, to visit it in 1989. So, we don't know much about the planet. Scientists used telescopes to study it instead. A team led by Erandi Chavez, a student at the Harvard-Smithsonian Center for Astrophysics, combined pictures from different telescopes to make a 29-year album of Neptune's changes from 1994 onwards. They compared these changes with the sun's cycles.
The sun goes through periods of high and low activity, called solar cycles, every 8 to 14 years. These cycles seem to match Neptune's cloud changes. In 2002 and 2015, Neptune had many clouds right after the sun's peak activity. Scientists think that the sun's ultraviolet light triggers a reaction that makes clouds in Neptune's skies.
During periods of low sun activity, Neptune's clouds disappear. But it's unclear why the current lack of clouds is so extreme compared to before. This study provides strong evidence that the sun's activity affects Neptune's clouds, revealing more about how the planet works.
Scientists who were not part of the study agree that this finding is significant. They say it's like the sun conducting an orchestra from 2.8 billion miles away. It shows that the sun controls even the farthest parts of our solar system.
But this study doesn't completely explain how these clouds form, and it's not definite that the sun is causing the changes. Scientists are waiting for the next solar maximum, which is predicted for 2025, to see if Neptune's clouds return.
Studying planets like Neptune takes time, and scientists are patient to learn more.
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