2015 RR245: New Dwarf Planet Discovered in Solar System’s Kuiper Belt

Astronomers have discovered a new dwarf planet in the Kuiper Belt, a vast ring of icy debris that is encircling the outer rim of our Solar System just beyond the gas giant Neptune.

The newfound dwarf planet, named 2015 RR245, is approximately 435 miles (700 km) in size, making it the 18th largest in the Kuiper Belt.

The orbit of 2015 RR245 takes it more than 120 times further from the Sun than Earth.

The object was first spotted in February 2016 by Dr. J.J. Kavelaars, an astronomer with the National Research Council of Canada.

It was found in September 2015 images from the Canada-France-Hawaii Telescope as part of the Outer Solar System Origins Survey (OSSOS).

“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,” said Dr. Michele Bannister from the University of Victoria, Canada.

“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.”

“Finding a new dwarf planet beyond Neptune sheds light on the early phases of planet formation,” added Brett Gladman from the University of British Columbia.

Rendering of the orbit of 2015 RR245 (orange line). Objects as bright or brighter than 2015 RR245 are labeled. Image credit: Alex Parker / OSSOS Team.

2015 RR245 now circles the Sun among the remnant population of tens of thousands of much smaller trans-Neptunian worlds, most of which orbit’s is unseen.

“The vast majority of the dwarf planets like 2015 RR245 were destroyed or thrown from the Solar System in the chaos that ensued as the giant planets moved out to their present positions,” the astronomers said.

“2015 RR245 is one of the few dwarf planets that has survived to the present day — along with Pluto and Eris, the largest known dwarf planets.”

After hundreds of years further than 7.46 billion miles (12 billion km, or 80 AU) from the Sun, 2015 RR245 is traveling towards its closest approach at 3.1 billion miles (5 billion km, or 34 AU), which it will reach around 2096. The object has been on its highly elliptical orbit for at least the last 100 million years.

The discovery was announced this week in the Minor Planet Electronic Circular (MPEC) newsletter.