Planet Neptune's Cloud Cover over Three Decades: Linked to Solar Cycle | Hubble

Planet Neptune's Cloud Cover over Three Decades: Linked to Solar Cycle | Hubble

This sequence of Hubble Space Telescope images chronicles the waxing and waning of the amount of cloud cover on Neptune. This long set of observations shows that the number of clouds grows increasingly following a peak in the solar cycle—where the Sun's level of activity rhythmically rises and falls over an 11-year period. The chemical changes are caused by photochemistry, which happens high in Neptune's upper atmosphere and takes time to form clouds.

The images reveal an intriguing pattern between seasonal changes in Neptune’s cloud cover and the solar cycle—the period when the Sun's magnetic field flips every 11 years as it becomes more tangled like a ball of yarn. This is evident in the increasing number of sunspots and increasing solar flare activity. As the cycle progresses, the Sun’s tempestuous behavior builds to a maximum, until the magnetic field beaks down and reverses polarity. Then the Sun settles back down to a minimum, only to start another cycle.

When it is stormy weather on the Sun, more intense ultraviolet (UV) radiation floods the solar system. The team found that two years after the solar cycle's peak, an increasing number of clouds appear on Neptune. The team further found a positive correlation between the number of clouds and the ice giant's brightness from the sunlight reflecting off it.

The link between Neptune and solar activity is surprising to planetary scientists because Neptune is our solar system's farthest major planet and receives sunlight with about 0.1% of the intensity Earth receives. Yet Neptune's global cloudy weather seems to be driven by solar activity, and not the planet's four seasons, which each last approximately 40 years.

In 1989, NASA's Voyager 2 spacecraft provided the first close-up images of linear, bright clouds, reminiscent of cirrus clouds on Earth, seen high in Neptune's atmosphere. They form above most of the methane in Neptune's atmosphere and reflect all colors of sunlight, which makes them white. Hubble picks up where the brief Voyager flyby left off by continually keeping an eye on the planet yearly.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Credits: NASA, European Space Agency, Erandi Chavez (UC Berkeley), Imke de Pater (UC Berkeley)

Release Date: Aug. 17, 2023

#NASA #Hubble #Astronomy #Space #Science #Sun #SolarCycle #UltravioletRadiation #Planet #Neptune #Atmosphere #Photochemistry #Clouds #SolarSystem #SpaceExploration #VoyagerSpacecraft #Cosmos #Universe #HST #HubbleSpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #Infographic #STEM #Education