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Neptune Cloud Cover and Solar Cycle Over Three Decades

This graphic shows a scientific plot in the form of a graph displaying changes in Neptune’s cloud cover compared to the 11-year-long repeating solar cycle of relative activity and inactivity on the Sun's surface. The vertical axis plots the level of ultraviolet radiation coming from the Sun. The horizonal axis is a timeline from the years 1994 to 2022. Seven Hubble photos of Neptune taken in the years 1994, 1998, 2002, 2006, 2010, 2015, and 2020 are plotted above the graph. The planet is blue (due to methane absorption of red light in its atmosphere) and the high-altitude, cirrus-like clouds are white. A comparison of Neptune's waxing and waning amount of cloud cover corresponds to peaks in the solar cycle. This graph clearly demonstrates the level of solar activity influences Neptune's weather.

This sequence of Hubble Space Telescope images chronicles the waxing and waning of the amount of cloud cover on Neptune. This nearly-30-year-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 Sun's level of ultraviolet radiation is plotted in the vertical axis. The 11-year cycle is plotted along the bottom from 1994 to 2022. The Hubble observations along the top, clearly show a correlation between cloud abundance and solar peak of activity.

The chemical changes are caused by photochemistry, which happens high in Neptune's upper atmosphere and takes time to form clouds.

 

About the Object

  • Distance
    DistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
    The semi-major axis of Neptune's orbit about the Sun is 30.06 astronomical units (roughly 2.8 billion miles or 4.5 billion kilometers).
  • Dimensions
    DimensionsThe physical size of the object or the apparent angle it subtends on the sky.
    Neptune has a diameter of roughly 30,800 miles (49,600 kilometers) at the equator.

About the Data

  • Data Description
    Data DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
    Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.

    The HST observations include those from several programs throughout three decades of observations including: 5221, 5329, 5831, 6219, 6650, 7324, 8634, 9393, 10170, 10534, 11156, 11630, 12675, 13937, 14044, 14334, 14756, 15262, 15502, 16057, 16084, 16454

  • Instrument
    InstrumentThe science instrument used to produce the data.
    WFPC2 and WFC3
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    Several observations spanning a time frame from 1994 to 2022
  • Filters
    FiltersThe camera filters that were used in the science observations.
    F845M, F850LP, F953N, CH4p15
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    Neptune
  • Object Description
    Object DescriptionThe type of astronomical object.
    Planet
  • Release Date
    August 17, 2023
  • Science Release
    Neptune’s Disappearing Clouds Linked to the Solar Cycle
    Read the release
  • Credit
    NASA, ESA, Erandi Chavez (UC Berkeley), Imke de Pater (UC Berkeley)

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This graphic shows a scientific plot in the form of a graph displaying changes in Neptune’s cloud cover compared to the 11-year-long repeating solar cycle of relative activity and inactivity on the Sun's surface. The vertical axis plots the level of ultraviolet radiation coming from the Sun. The horizonal axis is a timeline from the years 1994 to 2022. Seven Hubble photos of Neptune taken in the years 1994, 1998, 2002, 2006, 2010, 2015, and 2020 are plotted above the graph. The planet is blue (due to methane absorption of red light in its atmosphere) and the high-altitude, cirrus-like clouds are white. A comparison of Neptune's waxing and waning amount of cloud cover corresponds to peaks in the solar cycle. This graph clearly demonstrates the level of solar activity influences Neptune's weather.
Color Info
Color InfoA brief description of the methods used to convert telescope data into the color image being presented.

These images were acquired by the WFPC2 and WFC3 instruments on the Hubble Space Telescope. The color results from assigning a blue hue to a monochromatic (grayscale) image.

Related Images & Videos

This sequence of Hubble Space Telescope images chronicles the waxing and waning of the amount of cloud cover on Neptune. This display shows Hubble snapshots of the planet taken in the years 1994, 1998, 2000, 2002 (top row, from left to right) and 2006, 2010, 2015, 2020 (bottom row, from left to right). The planet is blue (due to methane absorption of red light in its atmosphere) and the high-altitude, cirrus-like clouds are white. A comparison of Neptune's cloud cover corresponds to peaks in the 11-year-long repeating solar cycle where the Sun's level of activity rhythmically rises and falls. Apparently, an increase in solar ultraviolet radiation causes chemical changes that affect Neptune's amount of cloud cover.

Neptune Cloud Cover Over Three Decades

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...

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Details

Last Updated
Mar 10, 2025
Contact
Media

Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov

Science Credit

NASA, ESA, LASP, Erandi Chavez (UC Berkeley), Imke de Pater (UC Berkeley)

Image Processing Credit

Joseph DePasquale (STScI)

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