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Astronomers spot an icy world beyond Pluto

The golden ellipse indicates the orbit of the newly confirmed object 2015 RR245. Click on the image for a larger version. (Credit: Alex Parker / OSSOS Team)
The golden ellipse indicates the orbit of the newly confirmed object 2015 RR245. Click on the image for a larger version. (Credit: Alex Parker / OSSOS Team)

Astronomers have found an icy world that ranges far beyond the orbit of Neptune and may well rank as a dwarf planet alongside Pluto.

The newly detected object, designated 2015 RR245, is thought to be less than a third the width of Pluto (435 miles vs. 1,474 miles), but its orbit is more eccentric. Its distance from the sun ranges from about 34 to more than 120 astronomical units, where each AU equals the distance between Earth and the sun. In comparison, Pluto’s orbit has a range of 30 to 50 AU.

Right now, 2015 RR245 is 80 AU from the sun and closing in, based on observations from the Canada-France-Hawaii Telescope on Hawaii’s big island. It should reach the nearest point in its 733-year orbit in the year 2096.

“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the sun. They let us piece together the history of our solar system. But almost all of these icy worlds are painfully small and faint: It’s really exciting to find one that’s large and bright enough that we can study it in detail,” Michele Bannister, an astronomer at the University of Victoria in British Columbia, said in a statement.

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By Alan Boyle

Mastermind of Cosmic Log, contributing editor at GeekWire, author of "The Case for Pluto: How a Little Planet Made a Big Difference," president of the Council for the Advancement of Science Writing. Check out "About Alan Boyle" for more fun facts.

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