Astronomers have discovered a tiny dwarf planet swinging through the outer reaches of our solar system.
The new world, which is half the size of Earth and 9 billion kilometres away, is on a path far beyond Neptune.
Its highly elliptical orbit is up to twice as far out as Pluto and takes the planet 700 years to circle the sun.
The newly-discovered dwarf planet will be at its closest point to our star in 2096 before curving back out to a distance of 12 billion kilometres.
Scientists believe that the giant ball of rock, which has been temporarily named 2015 RR245, is covered with ice and frozen nitrogen, possibly carbon monoxide and what has been described as “hydrocarbon gunk”.
The dwarf planet was first noticed last September by astronomers using an Hawaiian telescope as part of the Outer Solar Systems Origins Survey.
“It was really remarkable to see how bright this object was,” Michele Bannister, an astronomer on the team at the University of Victoria, Canada, told the Guardian. “It’s far brighter than the objects we normally find.”
Discovery images of RR245. The images show RR245’s slow motion across the sky over three hours.
The icy worlds beyond Neptune shed light on how the giant planets formed and then moved out from the sun, according to Bannister, who said they help scientists to piece together the history of the solar system:
“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.”
Most dwarf planets were either obliterated or ejected from the solar system when the giant planets moved into their current positions.
Five dwarf planets, Ceres, Pluto, Huamea, Makemake and Eris, are recognised by the International Astronomical Union, but there could be hundreds more.
Pluto’s status as a planet was downgraded in 2006 after astronomers discovered Eris, another dwarf planet.
To be classified as a planet, a cosmic body must orbit the sun but not be a satellite, have a sufficient mass to form a spherical shape under its own gravity, and have cleared the area around its orbit.
Pluto was declassified because it failed to satisfy the final qualification.
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