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Two more rings discovered around Uranus First additions to planet's ring system in nearly 20 years Updated: 2:03 p.m. ET Dec. 22, 2005 Astronomers aided by the Hubble Space Telescope have spied two more rings encircling Uranus, the first additions to the planet’s ring system in nearly two decades. The faint, dusty rings orbit outside of Uranus’ previously known rings, but within the orbits of its large moons, said Mark Showalter, an astronomer at the SETI Institute in Mountain View, Calif., who made the discovery. Details will appear on the journal Science's Web site, in advance of print publication. The...

The researchers report that they were studying the planet's rings, which are collectively called Eta, and discovered that they had an oddly shaped orbit -- not round or even circular. Instead, they describe it as sort of triangular. More study showed that the odd orbit of the rings was due to gravitational pull from Cressida -- one of the planet's moons. The gravitational impact is exaggerated, they note, due to the moon keeping pace with the orbit of the planet. The particles in the ring, on the other hand, move faster than the moon. This results in the moon tugging...

The appearance of a massive white cap on Uranus may seem alarming, but as planetary scientists are learning, this is what a prolonged summer looks like on the remote ice giant. Ice giants Uranus and Neptune have water-rich interiors coated with hydrogen, helium, and a pinch of methane, the latter of which gives these outer planets their distinctive cyan complexion. Unlike Earth, where seasons last just a few months, Neptune and Uranus experience seasons that last for decades, resulting in strange and intense atmospheric phenomena. New images released by the Outer Planet Atmospheres Legacy (OPAL) program highlight a evolving atmospheric...