Acting Up
There's something strange going on with Saturn's beautiful rings.
The gas giant experiences four seasons, much like our own except seven Earth years in length, thanks to its tilted axis. During the planet's equinox, when its rings tilt edge-on to the Sun, mysterious and fleeting new features appear in its rings called "spokes."
As NASA explains, astronomers have started referring to this period as "spoke season," something that has been observed since the early 1980s thanks to NASA's Voyager mission.
Now, the agency's Hubble Space Telescope has captured images of these strange lines crossing Saturn's rings, heralding the start of the planet's most puzzling transitional period.
Spo(o)ke(y) Season
We still don't know why these mysterious spokes appear, let alone why they're seasonal in nature.
"Despite years of excellent observations by the Cassini mission, the precise beginning and duration of the spoke season is still unpredictable, rather like predicting the first storm during hurricane season," said NASA senior planetary scientist Amy Simon in a statement.
But scientists do have an educated guess: the spokes may be the result of changes in Saturn's magnetic fields caused by solar wind. This electrically charged phenomenon, which triggers northern lights back on Earth, may cause icy particles in the planet's smallest rings to float above the rest of the rings, causing them to appear as fleeting shadows in Hubble's observations.
"It's a fascinating magic trick of nature we only see on Saturn — for now at least," Simon said.
Astronomers are now combining data taken by Hubble with observations made by its Cassini probe to get a better handle on the mysterious phenomenon.