Change in cloud cover on Neptune from 2002 to 2023
Imke de Pater, Elandi Chavez, Erin Redwing (University of California, Berkeley)/WM Keck Observatory
Neptune’s clouds have disappeared. Since the planet’s first detailed image was taken by Voyager 2 in 1989, its blue-green disk has been traversed by wispy white clouds, but the sky is now almost completely clear. I’m here. Astronomers suspect that Neptune’s cloudiness may be governed by the Sun’s 11-year cycle, even though Neptune is very far from the Sun.
Elandi Chavez Doctors at the University of California, Berkeley tracked Neptune’s cloud activity from 1994 to 2022. They examined archival images from his two observatories on Earth and the Hubble Space Telescope. The researchers found that cloud cover fluctuated regularly, with 2002 and 2015 being particularly cloudy, and 2007 and 2020 being particularly clear.
The 2020 cloud cover dip was the lowest ever observed, and with no white clouds to reflect sunlight, Neptune overall was the darkest we’ve seen so far. “Even now… the latest images we took in June of this year show that the clouds have not returned to their previous levels,” Chavez said in a statement. statement. “Previous periods of low cloud activity on Neptune have not been as dramatic or as long-lasting.”
And change happened unexpectedly quickly, especially in 2019. It disappeared to Neptune,” he said. Imke de Patel, and is also a member of the team at the University of California, Berkeley. “Basically, we’ve seen a decrease in cloud activity within a few months.”
This pattern appears to be roughly consistent with the 11-year cycle of activity on the Sun, but there is a two-year gap between the Sun’s and Neptune’s extrema. When the Sun is most active, more Neptune clouds begin to form, and when the Sun is least active, the Neptune clouds seem to disappear.
This most likely happens because when sunlight hits the upper part of Neptune’s atmosphere, its energy can initiate chemical reactions there, producing clouds of methane and other chemicals. These chemistries take time, resulting in a two-year delay. However, this correlation is surprising. Because Neptune is so far from the Sun, it receives only 1% of Earth’s sunlight. From there, the sun looks more like a particularly bright star in the night sky than the dazzling orb we see. view from earth.
The correlation has not yet been fully confirmed. Sunlight can certainly trigger reactions that create clouds on Neptune, but it can also darken clouds and haze, so cause and effect may not be so simple.
Neptune also occasionally experiences giant storms that begin deep in the atmosphere and then rise to the surface, but it is unclear what role they play. Researchers continue to monitor Neptune to better understand the intricacies of Neptune’s cloud layers.
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