Spokes Move Along Saturn’s Rings

Seven Hubble Space Telescope images, each taken about four minutes apart, are stitched together to show "spoke" features rotating around Saturn. The puzzling, transient features have defied easy characterization. Their rotation rate does not quite match up with the rotation of the rings or of the planet's magnetic field. The spokes are known to appear during the period leading up to and following the planet's equinox. With the northern hemisphere autumnal equinox approaching on May 6, 2025, scientists are hoping new observations by Hubble will help them to put the clues together and solve the spoke mystery—what are they, and why do they form? Hubble observations will be compared with those made by NASA's Cassini spacecraft in the period surrounding Saturn's last equinox, in 2009. With the Cassini mission completed, Hubble's annual observations of Saturn as part of its Outer Planet Atmospheres Legacy (OPAL) program will be crucial to studying and better understanding this dynamic world.