Astronomers discover new dwarf planet beyond orbit of Pluto


Astronomers are adding another member to the planetary roster with the discovery of 2015 RR245, a dwarf planet so far from the Sun it takes 700 years to make a full orbital journey. It is just the latest discovery of objects circumnavigating our star to be discovered in the Kuiper Belt.

“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the sun,” said Michele Bannister, a member of the team that discovered RR245 from the University of Victoria in British Columbia. “They let us piece together the history of our solar system.”

The numerical name is temporary and is given by the International Astronomical Union’s Minor Planet Center, which brings together astronomers, universities and organizations around the world. The planet was actually discovered at the Canada-France-Hawaii Telescope on Maunakea, Hawaii by the Outer Solar System Origins Survey (OSSOS), the internationally coordinated effort to locate these celestial objects.

Canada-France-Hawaii Telescope (CC BY 2.0 Vadim Kurland via Wikimedia Commons)
Canada-France-Hawaii Telescope (CC BY 2.0 Vadim Kurland via Wikimedia Commons)

The date assigned to the planet is actually according to the images recorded by the telescope, taken in September 2015. The movement between the slides was only realized by Dr. JJ Kavelaars (Canada) in February 2016.

“There it was on the screen — this dot of light moving so slowly that it had to be at least twice as far as Neptune from the Sun,” Bannister said, adding that little is known about the surface features. “It’s either small and shiny, or large and dull.”

Thanks to New Horizons, scientists have a bit more to speculate with. Images of Pluto and extensive analysis have given us a lot of insight into the surface composition and its unique relationship with its moon/co-planet Charon. Yet, knowing what’s going on with Pluto and Charon might not justify too specific a conclusion about this newly discovered dwarf planet.

“OSSOS was designed to map the orbital structure of the outer solar system to decipher its history.” said Prof. Brett Gladman of the University of British Columbia in Vancouver. “While not designed to efficiently detect dwarf planets, we’re delighted to have found one on such an interesting orbit.”

Multiple slides show movement of RR245, indicating the object is close enough to Earth that it is orbiting the sun (Credit: OSSOS team)
Multiple slides show movement of RR245, indicating the object is close enough to Earth that it is orbiting the sun. (Credit: OSSOS team)

New Horizon’s flyby of Pluto last year reawakened interest in astronomy for many people, as well as increased awareness for what is still a relatively new concept. The Kuiper Belt is the wide ring of icy and rocky objects that go around the sun beyond the orbit of Neptune (though the jury’s still out if anything can be beyond the orbit of Uranus).

The exact size of the object is difficult to estimate without another probe like New Horizons getting a closer look at the planet, but the initial estimate is it’s 435 km wide, about a third the size of Pluto. It is more than 120 AU away (an AU being the distance between the Earth and the sun).

The International Astronomical Union reorganized major objects in the solar system back in 2006 in conjunction with its infamous decision to reclassify Pluto, which was downgraded to a dwarf planet while asteroid belt object Ceres was upgraded to Pluto’s category. Most dwarf planets are in the Kuiper Belt, including Haumea (discovered 2004), Makemake (d. 2005), Eris (d. 2005) and Sedna (d. 2003).

As for future missions to the Kuiper Belt, New Horizons is still active. The probe was green lit on July 2 to set course for another recently discovered object, 2014 MU69, which is merely the size of Massachusetts’ Cape Cod Bay. The rendezvous is expected on January 1, 2019.


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