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upstart writes:

Hubble is investigating mysterious spokes in Saturn's rings:

Saturn is famous for its beautiful rings, but these rings have a strange feature: "spokes" which appear intermittently. These spots in the rings can be light or dark and can look like blobs or like lines stretching radially outward from the planet, and they appear in a regular cycle related to the planet's equinox. Now, the Hubble Space Telescope has the opportunity to study these oddities of the rings in more detail and researchers hope they can learn more about what causes these features.

The spokes were first noticed by the Cassini mission to Saturn in the 1980s, and since then they have been seen just before and after the equinox: the time at which day and night are of equal length across the planet because the sun is directly over the equator. On Earth, we experience two equinoxes each year, and the same is true for Saturn — but because Saturn is further out in its orbit and its year is much longer, its equinoxes occur just once every 15 Earth years.

[...] "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," Simon explained.

[...] The current theory of the spokes' origin is that they are related to Saturn's magnetic field, as charged particles from the sun interact with it in a way that could charge particles within the rings, shifting these particles out of place with the rest of the ring structure. But astronomers need to do more research to be sure of this theory — and to find out whether similar spokes could occur on other planets with rings, such as Neptune or Jupiter.

"It's a fascinating magic trick of nature we only see on Saturn —for now at least," Simon said.

Original Submission