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Spokes Spotted in Saturn’s Rings (Compass)

Compass image titled “Saturn: HST WFC3/UVIS—22 Sept. 2022” shows the planet Saturn with bright white rings and multi-colored main sphere. Spoke features (labeled “spokes” indicated in the white circle) 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 and orange, with brighter yellow 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. The compass graphic points to the object’s orientation on the celestial sphere.

NASA's Hubble Space Telescope has observation time devoted to Saturn each year, thanks to the Outer Planet Atmospheres Legacy (OPAL) program, and the dynamic gas giant planet always shows us something new. This latest image heralds the start of Saturn's "spoke season" with the appearance of two smudgy spokes (shown in the white circle) in the B ring, on the left in the image.

The shape and shading of spokes varies—they can appear light or dark, depending on the viewing angle, and sometimes appear more like blobs than classic radial spoke shapes, as seen here. The ephemeral features don't last long, but as the planet's autumnal equinox approaches on May 6, 2025, more will appear. Scientists will be looking for clues to explain the cause and nature of the spokes. It's suspected they are ring material that is temporarily charged and levitated by interaction between Saturn's magnetic field and the solar wind, but this hypothesis has not been confirmed.

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: 16790 (A. Simon).
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 Sept. 2022
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
February 9, 2023
Science Release
Hubble Captures the Start of a New Spoke Season at Saturn
Read the release
Credit
NASA, ESA, Amy Simon (NASA-GSFC); Image Processing: Alyssa Pagan (STScI)

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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

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