Hubble Spots Enigmatic “Spokes” in Saturn’s Rings

” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Saturn, 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 in the B ring, on the left in the image.

The spokes are enigmatic features that appear across Saturn’s rings. Their presence and appearance varies with the seasons — like Earth, Saturn is tilted on its axis and therefore has four seasons. With Saturn’s much larger orbit, each season lasts approximately seven Earth years. Equinox occurs when the rings are tilted edge-on to the Sun and marks the height of spokes’ visibility, while during a solstice when the Sun is at its highest or lowest latitude, the spokes disappear.

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 caused by interaction between Saturn’s magnetic field and the solar wind, which also causes aurorae to appear on the planet. The hypothesis is that spokes are the smallest, dust-sized, icy ring particles being temporarily electrically charged and levitated, but this has not been confirmed.

Saturn’s last equinox occurred in 2009, while the NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA/ESA/ASI CassiniThe Cassini–Huygens Mission, generally called Cassini, was a joint mission between NASA, the European Space Agency and the Italian Space Agency to study the Saturn system. Launched in 1997, Cassin provided astronomers with a massive amount of data about Saturn and its rings, its magnetosphere, and its moons. Cassini reached the end of its journey in 2017 when it deliberately dived into Saturn's atmosphere, where it disintegrated like a meteor.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Cassini spacecraft was orbiting the gas giant planet for close-up reconnaissance. With Cassini’s mission completed in 2017, Hubble is continuing the work of long-term monitoring of changes on Saturn and the other outer planets.

For more on this topic, see Saturn’s Rings Are Acting Strange.