New Study: Neptune’s Weather Driven By Solar Activity

Cap Allon

A new paper published August 17 in the research journal Icarus offers proof that solar activity drives planetary weather — even on a planet such as Neptune, which orbits 2.5 billion miles away from the Sun.

26-years of images taken by the Hubble Space Telescope reveal clouds forming perfectly in sync with the 11-year solar cycle:

High solar activity = more clouds on Neptune.


With Neptune being our solar system’s farthest major planet, this direct connection between its climate and solar activity has surprised planetary scientists.

Neptune receives only 0.1% of the sunlight Earth receives, explains Dr Tony Phillips of spaceweather.com. Yet Neptune’s cloudiness is mostly driven by solar activity, rather than the planet’s 4 seasons, which each last approximately 40 years.

“This is extremely exciting and unexpected,” said Erandi Chavez, a graduate student at Harvard-Smithsonian’s Center for Astrophysics, who led the study when she was a student at UC Berkeley.

Chavez and her team confirmed Hubble’s findings using data from the Webb Space Telescope, the Keck Observatory, and the Lick Observatory — the link between the Sun’s output and Neptune’s clouds seems solid, and it looks to be related to solar ultraviolet radiation, which peaks when sunspot counts are high.

“Our findings support the theory that the Sun’s UV rays, when strong enough, may be triggering a photochemical reaction that produces Neptune’s clouds,” said Imke de Pater, emeritus professor of astronomy at UC Berkeley, a senior co-author of the study.

Based on the data so far, it takes two years for Neptune’s clouds to fully form once the solar cycle reaches its peak. Solar Cycle 25 is fast-approaching its maximum now, with a peak expected in 2024. This means Neptune’s ‘cloudy season’ is about to begin.


This newly discovered link once again demonstrates the ruling influence the Sun has over complex planetary climate systems.

It also goes to show how different the influence can be planet to planet, dependent, it appears, on its atmospheric chemical composition. The effects on Neptune, for example, run counter to those documented here on Earth. Svensmark et al–for one–have clearly shown that it is low solar activity that leads to an increase in cloudiness on our home planet, which in turn leads to cooling via a reduction of incoming solar wind and an anti-correlated influx of cloud-nucleating cosmic rays:

Cosmic Ray Flux and Global Cooling: the implications are upon us


The Science is never settled, no matter the degree of propaganda.

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