Strange things are happening to the rings of Uranus.
Once every 42 years, the planet’s tilted angle lets earthbound observers briefly catch three edge-on views of the rings instead of the usual direct view that makes them appear as if they were sunlit paintings on the flat rim of a dinner plate.
The time for the rare views is right now, and a team of astronomers from the University of California at Berkeley and the SETI Institute in Mountain View, Calif., has seen some dramatic changes – some rings are growing brighter, at least one is fading away, and another is either newly formed or unexpectedly moving outward from Uranus by thousands of miles.
At the same time, a broad, diffuse cloud of microscopic dust particles seems to be pervading the entire ring system.
Imke de Pater, a UC planetary astronomer, and Mark Showalter at the SETI Institute, who has been studying Uranus for 20 years, reported Thursday in the online journal Science Express that the changes are not fully understood.
De Pater, who is in Potsdam, Germany, said in a phone interview that “the ring system looks completely different” from the way it did 21 years ago when the Voyager 2 spacecraft flew past Uranus and took thousands of pictures of its rings and moons before it flew on to the edge of the solar system.
“The rings are exquisite now,” de Pater said, “and the innermost ring, called zeta, seems to have moved since Voyager flew past.” Back then, she said, the Voyager images in 1986 showed that the zeta ring surrounded the planet about 23,000 miles out, but now the latest infrared images from the powerful Keck telescope atop Mauna Kea on the Big Island of Hawaii show that the same ring is nearly 25,000 miles out.
It’s possible, de Pater said, that incoming meteorites disturbed the ring and thrust it outward. Showalter suggested that some massive object may have crashed into the surface of Uranus and ejected a shower of dusty debris that has formed an entirely new ring while the old zeta ring has simply faded.
