All of Neptune’s clouds disappeared, and scientists blamed the sun

Astronomers announced this unexpected update on Thursday, August 17. All of Neptune’s clouds have disappeared, and for the first time in three decades, Neptune is completely cloud-free.

Scientists observed detailed images of the planet between 1994 and 2022, and noticed a strange pattern beginning in 2019. Around the planet’s mid-latitudes, cloud coverage seemed to be starting to fade. In the end, all evidence of the clouds completely disappeared, Space.com mentioned.

Since 2019, scientists have seen only one speck of soft white drift around the planet’s south pole.

“I was surprised by how quickly the clouds on Neptune were disappearing,” Emke de Pater, professor emeritus of astronomy at UC Berkeley and senior author of a study on the findings, said in a statement. “We’ve basically seen a drop in cloud activity over the course of a few months.”

Scientists decided to dig deeper. To monitor the evolution of Neptune’s appearance, Chavez and her team analyzed Keck Observatory images taken from 2002 to 2022, archival observations by the Hubble Space Telescope that began in 1994, and data from the Lick Observatory in California from 2018 to 2019. They showed that Neptune’s clouds are closely related to the way our Sun behaves. during its 11-year activity cycle.

The pattern more or less matches the sun’s 11-year activity cycle, the scientist said, albeit with a two-year gap between the sun’s extremes and Neptune’s. It seems that when the Sun is more active, more clouds begin to form on Neptune, and when it is less active, Neptune’s clouds dissipate, new world The report said.

according to NASAIts release, when the sun is stormy, more intense ultraviolet radiation floods the solar system. The team found that two years after the peak of the solar cycle, an increasing number of clouds appear on Neptune. The team also found a positive correlation between the number of clouds and the ice giant’s brightness from sunlight reflecting off it.

“This remarkable data gives us the strongest evidence yet that Neptune’s cloud cover is linked to the sun’s cycle,” said de Pater. “Our findings support the theory that the sun’s ultraviolet radiation, when strong enough, possibly triggers a photochemical reaction that produces Neptune’s clouds.”

Scientists discovered the relationship between the solar cycle and Neptune’s cloudy weather pattern by looking at 2.5 cycles of cloud activity recorded over 29 years of Neptune observations. During this time, the planet’s reflectivity increased in 2002 and then died down in 2007. Neptune brightened again in 2015, then darkened in 2020 to the lowest level ever observed, which is when most of the clouds cleared.

Changes in Neptune’s brightness caused by the Sun appear to rise and fall relatively in sync with the coming and going of clouds on the planet. However, there is a two-year lag between the peak of the solar cycle and the abundance of clouds seen on Neptune. The chemical changes are caused by photochemistry, which occurs high in Neptune’s atmosphere and takes time for clouds to form.

“It’s great to be able to use telescopes on Earth to study the climate of a world more than 2.5 billion miles away,” said Carlos Alvarez, an astronomer at the Keck Observatory and co-author of the study. “Advances in technology and observations have enabled us to constrain models of Neptune’s atmosphere, which are key to understanding the relationship between the ice giant’s climate and the solar cycle.”

However, more work is necessary. For example, while an increase in the sun’s ultraviolet light can produce more clouds and haze, it can also darken them, thus reducing the overall brightness of Neptune. Storms on Neptune rising from the deep atmosphere affect cloud cover, but are not associated with photosynthetic clouds, and thus may complicate correlation studies with the solar cycle. Continuous observations of Neptune are also needed to see how long the near absence of clouds will last.

The research team continues to track Neptune’s cloud activity. “We saw more clouds in the latest Keck images taken during the same time that NASA’s James Webb Space Telescope observed the planet; these clouds were seen in particular at northern latitudes and at high altitudes, as would be expected from the observed increase in the outflow of solar ultraviolet radiation for about the past two years,” De Pater said.

The combined data from the Hubble, Webb Space Telescope, Keck Observatory and Lick Observatory will enable further investigations into the physics and chemistry that lead to Neptune’s dynamic appearance, which in turn may help astronomers deepen understanding not only of Neptune but also of the outer planets where many planets are thought to be. Outside our solar system it has Neptune-like qualities.

The results have been published in the journal Icarus.