The gas giant Saturn is known for its iconic ring system. However, its B ring can have splotches and streaks of darker or lighter material, known as spokes, that may be tied to dust interactions with the planet’s magnetic field. A new image of Saturn, taken by the NASA/ESA Hubble Space Telescope on October 22, 2023, reveals the ring spokes.
Saturn’s spokes — named so because they look like bicycle spokes — are transient features that rotate along with the rings.
Their ghostly appearance only persists for two or three rotations around the giant planet.
During active periods, freshly-formed spokes continuously add to the pattern.
The ring spokes were first photographed in 1981 by NASA’s Voyager 2 spacecraft.
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 side of the rings.
Long-term monitoring show that both the number and contrast of the spokes vary with Saturn’s seasons.
“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 Dr. Amy Simon, an astronomer at NASA’s Goddard Space Flight Center and lead scientist of the OPAL program.
“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…
Read the full article here