Astronomers using the Canada-France-Hawaii Telescope on Hawaii’s Mauna Kea announced today that a new trans-Neptunian dwarf planet has been discovered.
Known as RR245, the frigid, newly-discovered world was discovered as part of the ongoing Outer Solar System Origins Survey (OSSOS). With an orbital period of 700 years and a semi-major axis of 11.8 billion km (almost twice the distance to Pluto), the icy planet will be at its perihelion point (closest approach to the sun) of 5 billion km from the sun in 2096. Its aphelion point (or greatest distance from the sun) is a staggering 116 AU (Astronomical Units) from the sun!
Designated as 2015 RR245 and first sighted in February 2016 by Dr. JJ Kavelaars of Canada’s National Research Council in the OSSOS images from September 2015, RR245 is the 18th largest object discovered to date in the Kuiper Belt, the region of the solar system beyond Pluto. A dwarf planet is defined as an object with a mass range of planets or moons, sufficient for the object’s self-gravity to have it form as a spheroidal body. Unlike moons however, dwarf planets are in direct orbit around our sun. Unlike the major planets though, dwarf planets have not cleared out the debris in their orbital paths. The guidelines set forth in the 2006 IAU definition of planets, those that caused Pluto to lose its major planet status, have described these terms.
Astronomer at the University of Victoria, British Columbia and postdoctoral fellow with OSSOS, Michele Bannister said of the newly discovered dwarf planet:
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.
Just how big is RR-245? That remains an open question as we have insufficient information about its physical properties (mass, density, surface composition) to make a precise size determination but current estimates put it at 700 km. What we can say about it by way of paraphrasing Dr. Bannister, it is either small-to-average and shiny or large and dull.