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Are 2 Small, Dark Moons Hiding In The Rings Of Uranus?

The planet has 27 known moons. But are there more?

18/10/2016 7:04 PM AEDT
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UNSPECIFIED - JULY 03: Hubble Space Telescope view revealing Uranus surrounded by its four major rings and by 10 of its 17 known satellites. This false-colour image was generated by Erich Karkoschka using data taken on 8 August 1998, with Hubble's Near Infrared Camera and Multi-Object Spectrometer. Hubble found about 20 clouds - nearly as many clouds on Uranus as the previous total in the history of modern observations. The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Space Flight Center for NASA's Office of Space Science. (Photo by SSPL/Getty Images)
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A false-color image taken by Voyager shows the rings of Uranus. Astronomers believe they've found evidence of two previously unknown moons hidden in the rings.

Uranus might have a secret.

A new analysis of data from the Voyager 2 spacecraft, which passed Uranus in 1986, revealed that two of the planet’s rings have a telltale wavy pattern that could indicate the presence of a pair of small moons. These dark moons or “moonlets” would be smaller than Manhattan ― with diameters between just 2.5 and 8.5 miles ― and orbit outside the alpha and beta rings:  

NASAJPL
The alpha and beta rings, circled in this 1986 image taken by Voyager, could be hiding two very small moons. 

These moons are pretty tiny,” Rob Chancia, one of the two University of Idaho researchers to make the discovery, told New Scientist. 

Chancia said the moons were so small that they wouldn’t have been picked up by Voyager’s cameras when the spacecraft passed Uranus three decades ago, coming within 50,600 miles of the planet’s cloudtops. 

The moons also might have blended in with the rings.

“Not only are Uranus’ rings dark, so are most of the little satellites that are in that region,” Matthew Hedman, the other researcher involved in the discovery, told the magazine.

The two published their findings on arXiv.org

“Future Earth-based observations may be more likely to detect these moons” than re-examining the Voyager images, Chancia and Hedman wrote in the article, which was accepted for publication in the Astronomical Journal. 

NASAJPLSTScI
Uranus and its rings seen in a false-color image taken by the Hubble Space Telescope in 1995. The rings are normally very dark. 

If confirmed, the two moons would be the planet’s 28th and 29th known satellites.

While most moons in the solar system are named for characters in Greek mythology, most of the 27 moons of Uranus have names taken from Shakespeare, including Oberon and Titania, the two largest moons.

Eight of the smaller moons are grouped so closely together that NASA said “astronomers don’t yet understand how the little moons have managed to avoid crashing into each other.”

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