Newly spotted distant dwarf planet orbits the Sun every 700 years

It's so lonely and cold out here I don't even have a name

Dwarf planet 2015 RR245
The big wheel; 2015 RR245's huge orbit. Image: Alex Parker, OSSOS

Astroboffins are excited about a newly-discovered dwarf planet, despite not knowing what it looks like.

The discovery of 2015 RR245 comes from the Outer Solar System Origins Survey (OSSOS), which back in March spotted alignments in Kuiper Belt Objects that fuelled the controversial “planet X” theory.

The new object has so large an orbit that astronomers don't yet have enough data to do much more than say residents would only get to sing “Happy Birthday” about once every 700 Earth-years.

At least 2015 RR245 (its Astronomical Union's Minor Planet Center designation), was spotted not by an algorithm, but by a human. As Canada's University of Victoria explains, researcher and adjunct professor JJ Kavelaars spotted the object as a point of light moving on-screen.

Astronomy postdoc Michele Bannister put it like this: “There it was on the screen, this dot of light, moving so slow that it had to be at least twice as far as Neptune from the sun.”

So far, the researchers have worked out that the planet's orbit takes it more than 120 Earth-orbits away from the Sun, and it'll get a name when enough data has been gathered to characterise its orbit properly.

Since just one-seven-hundredth of 2015 RR245's orbit has been observed, it will be a few years before its orbit is known well enough for the object to get a name.

The astroboffins will also be studying the roughly 700 km object to decide whether it's smaller and bright, or larger and dull. That will wait for better measurement of its surface properties.

Bannister explained that since most distant dwarves are “painfully small and faint … it’s really exciting to find one that's large and bright enough to study in detail”.

Such planets can help us understand what “makes an object go from being an unchanging lumpy mashed-together structure of ice and rock to having geological processes that separate and rearrange its material, as happens on Pluto.”

The images that spotted the slow-moving lump were taken by the Canada-France-Hawaii Telescope (location: Maunakea, Hawaii).

In 2013, that telescope spotted a much lonelier planet – one apparently orbiting no sun at all. ®




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