In the far limits of the Solar System, on Neptune, astronomers have seen clouds vanish. Images taken by the Hubble telescope over time revealed the phenomenon.

The 11-year solar cycle, which is caused by the waxing and waning of the Sun’s entangled magnetic fields, has an intriguing relationship with Neptune’s altering cloud abundance, which has been observed by astronomers.

Based on three decades of Neptune observations, this ground-breaking finding was made possible thanks to the Hubble Space Telescope, the W. M. Keck Observatory in Hawaii, and the Lick Observatory in California.

The global overcast weather of Neptune, the farthest major planet in our solar system, appears to be controlled by solar activity rather than by its own four seasons, which each endure for around 40 years. Neptune receives just about 0.1% of the sunlight that Earth does.

There are a few clouds floating over Neptune’s south pole right now, but the huge planet’s cloud cover is currently very low.

A group of astronomers from the University of California (UC) Berkeley found that the icy giant’s mid-latitudes typically have an abundance of clouds that started to diminish in 2019. Imke de Pater, senior author of the study and emeritus professor of astronomy at UC Berkeley, remarked, “I was shocked by how swiftly clouds dissipated on Neptune. “We basically noticed a decline in cloud activity within a few months.”

The most current photographs, which were taken in June, still reveal that the clouds haven’t recovered to their pre-disaster levels, according to Erandi Chavez, a graduate student at the Center for Astrophysics | Harvard-Smithsonian (CfA) in Cambridge. This was detected despite the passage of four years.

The researchers examined data from the Lick Observatory in California from 2018 to 2019, photos from the Keck Observatory in California from 2002 to 2022, and archived Hubble Space Telescope observations starting in 1994.

The periodic variations in Neptune’s cloud cover and the solar cycle, which occurs every 11 years as a result of the Sun’s rising number of sunspots and solar flare activity, were discovered to follow a fascinating pattern.

More stronger ultraviolet (UV) radiation enters the solar system when the Sun is inclement. The research team discovered that Neptune experiences an increase in cloud cover two years following the solar cycle’s apex. Additionally, they discovered a link between the quantity of clouds and the brightness of the ice giant as seen in the sunlight reflecting off of it.

According to de Pater, “our results lend support to the idea that, under some conditions, the Sun’s UV rays may be causing a photochemical reaction that results in Neptune’s clouds. But additional work is required. For instance, an increase in UV sunlight may result in more clouds and haze, but it may also cause them to become darker, lowering Neptune’s total brightness.