The rings that girdle Uranus are nowhere near as optically spectacular as those that surround Saturn. Indeed, they reflect so little light that they were not discovered until 1977.
Now, however, a composite of new images taken by the Atacama Large Millimetre/submillimetre Array (ALMA) and the Very Large Telescope (VLT), both in Chile, have provided new details.
“Saturn’s mainly icy rings are broad, bright and have a range of particle sizes, from micron-sized dust in the innermost D ring, to tens of metres in size in the main rings,” says astronomer Imke de Pater, from the University of California Berkeley, US.
“The small end is missing in the main rings of Uranus; the brightest ring, epsilon, is composed of golf ball-sized and larger rocks.”
Perhaps the most interesting finding to come out of the research by de Pater and his colleagues is a firm estimate of the temperature of the rings.
They may be glowing, but that doesn’t mean they’re warm. In a paper currently lodged on the Cornell University preprint site arXiv, they report that the rings of Uranus are just 77 degrees Kelvin above absolute zero – or minus-196 degrees Celsius.
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