Suggested Searches

1 min read

Saturn Compass Image

Compass image titled "Saturn - October 22, 2023: HST WFC3/UVIS" shows the planet Saturn with bright white rings, multi-colored main sphere, and moons Mimas, Dione, and Enceladus. Spoke features (labeled "spokes" indicated in the white circles on the left and right sides) appear like faint gray smudges against the ring's bright backdrop, about midway from the planet to the rings' outer edge. Above the rings plane, the planet's bands are shades of red, orange and yellow, with white nearer the equator. This image is a composite of separate exposures acquired by the Hubble Space Telescope using the WFC3/UVIS instrument. Several filters were used to sample specific wavelength ranges. The color results from assigning different colors to each monochromatic (grayscale) image associated with an individual filter. The assigned colors listed in the upper right corner of the image are: red: F631N; green: F502N; blue: F395N. Compass graphic points to the object's orientation on the celestial sphere. Background is black.

This photo of Saturn was taken by NASA's Hubble Space Telescope on October 22, 2023, when the ringed planet was approximately 850 million miles from Earth. Hubble's ultra-sharp vision reveals a phenomenon called ring spokes.

Saturn's spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.

In 1981, NASA's Voyager 2 first photographed the ring spokes. NASA's Cassini orbiter also saw the spokes during its 13-year-long mission that ended in 2017.

Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble's Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.

Hubble's crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring show that both the number and contrast of the spokes vary with Saturn's seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.

"We are heading towards Saturn equinox, when we'd expect maximum spoke activity, with higher frequency and darker spokes appearing over the next few years," said the OPAL program lead scientist, Amy Simon of NASA's Goddard Space Flight Center in Greenbelt, Maryland.

This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth's diameter!

The leading theory is that spokes are tied to Saturn's powerful magnetic field, with some sort of solar interaction with the magnetic field that gives you the spokes. When it's near the equinox on Saturn, the planet and its rings are less tilted away from the Sun. In this configuration, the solar wind may more strongly batter Saturn's immense magnetic field, enhancing spoke formation.

Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery.

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.

    This image was created with Hubble data from proposal: 16995 (A. Simon). Image Processing: Joseph DePasquale (STScI)

  • Instrument
    InstrumentThe science instrument used to produce the data.
    WFC3/UVIS
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    22 October 2023
  • Filters
    FiltersThe camera filters that were used in the science observations.
    F395N, F502N, F631N
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    Saturn
  • Object Description
    Object DescriptionThe type of astronomical object.
    Gas giant with rings
  • Release Date
    December 21, 2023
  • Science Release
    NASA’s Hubble Watches ‘Spoke Season’ on Saturn
  • Credits
    NASA, ESA, STScI, Amy Simon (NASA-GSFC)

Downloads

  • Full Res (For Display), 1755 × 987
    png (403.12 KB)
  • Full Res (For Print), 1755 × 987
    tif (445.58 KB)
Compass image titled "Saturn - October 22, 2023: HST WFC3/UVIS" shows the planet Saturn with bright white rings, multi-colored main sphere, and moons Mimas, Dione, and Enceladus. Spoke features (labeled "spokes" indicated in the white circles on the left and right sides) appear like faint gray smudges against the ring's bright backdrop, about midway from the planet to the rings' outer edge. Above the rings plane, the planet's bands are shades of red, orange and yellow, with white nearer the equator. This image is a composite of separate exposures acquired by the Hubble Space Telescope using the WFC3/UVIS instrument. Several filters were used to sample specific wavelength ranges. The color results from assigning different colors to each monochromatic (grayscale) image associated with an individual filter. The assigned colors listed in the upper right corner of the image are: red: F631N; green: F502N; blue: F395N. Compass graphic points to the object's orientation on the celestial sphere. Background is black.
Color Info
Color InfoA brief description of the methods used to convert telescope data into the color image being presented.

These images are a composite of separate exposures acquired by the Hubble Space Telescope using the WFC3/UVIS instrument. Several filters were used to sample specific wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:   Red: F631N, Green: F502N, Blue: F395N

Share

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, STScI, Amy Simon (NASA-GSFC)