Why did the ice giant Neptune’s clouds suddenly disappear?

Those over 40 may miss the first distributed close-up images of the planet NeptuneNeptune there NASANASA During the summer of 1989, Voyager 2 passed about 4,950 km above Neptune’s north pole. It was found from these images thatAtmosphereAtmosphere The ice giant was much more active than previously thought, and data collected by the probe showed that Neptune emitted slightly more energy than it received from the Sun.

You can clearly see the equivalent of Jupiter’s Great Red Spot, but here ColourColour Dark blue background resulting from Neptune’s atmosphere having a large amount of methane. of the cloudsthe clouds Whites were also clearly visible in the upper atmosphere. All this data puzzled planetary scientists, as they also wondered what the source of it could be.internal energyinternal energy of Neptune which made it hotter than the Sun and the light from our star could also clearly contribute chemistrychemistry associated with the existence of active and complex linear and brilliant clouds, reminiscent of cirruscirrus on the earth.

a large faint star barely 1/30th the diameter of a full moon

Located about 4.5 billion kilometers from the Sun, Neptune receives only 0.1% of the radiation measured on Earth. a supervisor in To revolve aroundTo revolve aroundFor example, on Neptune’s moon Triton, the Sun would appear barely 1/30 as a large faint star.^I of diameter full moonfull moon,

To better understand Neptune’s mysteries, planetary scientists have worked since OverviewOverview Of Voyager 2Voyager 2To periodically monitor its atmosphere first with the Hubble telescope and then with instruments from the WM Keck Observatory in Hawaii that allow adaptive optics.

Planetary scientists, such as the renowned Imke de Pater, Astronomy and Emeritus Professor of Terrestrial and Planetary Sciences at the University of California at Berkeley (and author of a famous treatise on planetary science), are therefore studying modifications of Neptune’s activity, and in 2019 I got a surprise. Within a few months, much of the ice giant cloud had disappeared, and much of it remains today.

Today in the famous newspaper Icarus these 30 years of observation and review of this mysterious disappearance has been published. The article in question can be found in open access on arXiv.

Cloud cover is controlled by the sunspot cycle

Data collected during the monitoring program now strongly suggest that the disappearance of Neptune’s clouds is cyclical and controlled by the 11-year solar cycle known from sunspots. This cycle is controlled by the mechanisms present on the Sun at its core. Magnetic FieldMagnetic Field By the physics of the solar plasma in our star’s and turbulent magnetic fields. There is an entanglement of field lines in relation to the differential rotation of the inner layers of the Sun, which concentrates energy which is eventually released.

The publication also includes a statement from NASA Icarus And we can read Emke de Pater’s declarations thus: I was amazed at how quickly the clouds on Neptune disappeared. We’ve basically seen a decline in cloud activity over the course of a few months. ,

, Even now, four years later, the most recent images we took last June still show that the clouds have not returned to their previous levels. This is extremely exciting and unexpected, especially since Neptune’s previous periods of low cloud activity were not so dramatic and prolonged. “, says Erandi Chávez, stationed in the centerastrophysicsastrophysics – Harvard-Smithsonian (CFA) in Cambridge, Massachusetts (USA) and who edited the article forIcarus When she was an astronomy student at UC Berkeley.

The press release continues with re-clarifications from Imke de Pater regarding comments made since 1994: ” These remarkable data give us the strongest evidence yet SolidSolid So far Neptune’s cloud cover is related to the circle of the Sun. Our findings support the theory that UV rays from the Sun, when strong enough, can trigger a photochemical reaction that forms Neptune’s clouds. ,

However, there is a gap of two years between its peak solar radiationsolar radiation and the number of clouds observed on Neptune, which can be explained by the amount of time it takes to generate the amount of energy injected by solar radiation into Neptune’s atmosphere. chemical reactionschemical reactions Required for cloud formation.

Researchers will continue to study Neptune’s clouds with combined data from Hubble, the James Webb Space Telescope.Keck ObservatoryKeck Observatory and Lick Observatory. Theoretical analysis of these data will also help us to understand in future exoplanetsexoplanets Neptune-like.