Neptune’s blue clouds are gone – that’s why

in one The statement was issued on Thursday A research team from the University of Berkeley in the US state of California announced unexpected news about the planet Neptune. A more detailed article on this topic will be published in (already available online) November issue Appearing in Icarus Magazine.

Then, examining images taken between 1994 and 2022, the researchers found a strange pattern that began in 2019. First, it affected only the mid-latitudes of Neptune, and then spread to the entire planet.

Very slowly at first, then faster and faster, the planet’s azure clouds completely disappeared. Emke de Pater, professor emeritus of astronomy at the University of Berkeley and lead author of the study about the survey findings, said she was “surprised by how quickly the clouds on Neptune were disappearing.” Within a few months, cloud activity dropped to zero.

A drastic change in Neptune’s appearance was observed in late 2019 and persisted until June 2023. From before 2002 to late 2019, Neptune displayed several latitude-arranged cloud features, as seen in this set of images at 1.63 microns (microns) Captured using the adaptive optics of the Keck II telescope and NIRC2. After that, the clouds did not appear until near the South Pole. (Image credit: Imke de Pater, Erandi Chavez, Erin Redwing (UC Berkeley) / WM Keck Observatory)

A closer look revealed that the disappearance of Neptune’s clouds is closely related to the behavior of our Sun during its 11-year activity cycle. Within these eleven years, the Sun’s poles reverse – the North Pole becomes the South Pole and vice versa.

This change in the magnetic fields of our host star is not without consequences. Due to changes in the magnetic field, for example, there is an increasing number and higher intensity of so-called solar flares (flares), which are incredibly powerful radiation bursts in space.

These flares can be powerful enough to disrupt orbiting satellites. They are often associated with giant eruptions of solar plasma known as coronal mass ejections. Many charged particles can hit the Earth, causing temporary small disturbances in communication lines.

Because despite its homogeneous optics when viewed from Earth, the Sun is not a scorching hot planet, but merely a vast spherical ocean of charged particles called a plasma.

Based on the latest findings on Neptune, it is likely a different phenomenon, which is also caused by changes in the magnetic field. Thus, the Sun emits such an amount of ultraviolet radiation that, given the enormous mass of the Sun, it literally “floods” the rest of the solar system. It seems that this also applies to Neptune, although it is about 4.5 billion kilometers from the Sun.

In their investigations, the researchers used images of the planet from about 30 years ago, from NASA’s Hubble Space Telescope, the WM Keck Observatory in Hawaii, and some others.

They found a clear relationship between the number of clouds on Neptune and the point in time at which the Sun’s solar cycle occurs. About two years after the peak of the cycle—that is, the main event of the magnetic field reversal—Neptune’s solid cloud cover should have been detectable.

Only after this peak did the clouds seem to clear. The researchers hypothesized that the sun’s ultraviolet radiation — which is strongest when the sun is at its highest — triggers a photochemical reaction resulting in the absorption of energy in the form of light, which then leads to the formation of Neptune’s cloud cover.

“These impressive data provide the strongest evidence yet that Neptune’s cloud cover is connected to the solar cycle,” said de Pater. In addition, Neptune seemed to appear brighter the more clouds it had, because sunlight reflected off those clouds more.

“So far, four years later, the latest images we took in June of this year show that the clouds have not yet returned to their previous levels,” said Irandi Chavez, a graduate student at the Joint Center for Astrophysics and the Smithsonian Institution. .

Even without their own expertise, anyone can clearly see the changes shown in the images provided by the team. We owe this to the availability of observatories such as the Keck Observatory and the Hubble Space Telescope.

“It’s great to use telescopes on Earth to study the climate of a world more than 2.5 billion kilometers away,” said Carlos Alvarez, an astronomer at the Keck Observatory and co-author of the study.

Going forward, Alvarez and his colleagues will continue to monitor Neptune’s cloud activity to determine when previously observed features will return. In fact, over the past several years, they’ve already seen clouds reappear as UV output from the sun increases.

“In the latest Keck image, taken at the same time that NASA’s James Webb Space Telescope was observing the planet, we saw more clouds,” said de Pater. “These clouds were particularly visible at northern latitudes and at high altitudes, as would be expected based on the observed increase in solar ultraviolet light flux over the past two years or so.”