Kepler and Herschel Telescopes Team Up to Spy on a Dwarf Planet

Astronomers just announced that an unnamed object in the outer reaches of the Solar System is larger than previously thought. New research published in the Astrophysical Journal shows it's only slightly smaller than Pluto and Eris, which could upgrade it to dwarf planet status. If so, it would take the title of third largest dwarf planet away from Makemake.

Dubbed 2007 OR10, this enigmatic world is the largest body in the Solar System without a name. Jokingly referred to as "Snow White", due to its perceived brightness and because it was the seventh potential dwarf planet discovered, the world was first spotted in 2007 by a team of astronomers led by Mike Brown—the same Mike Brown who demoted Pluto and who discovered evidence of a massive planet lurking in the outer Solar System.

So how is it that astronomers misjudged the size of this icy world? It's not the first time our Solar System surprised us: recently, astronomers discovered a hidden moon lurking in Makemake's shadow. Objects like 2007 OR10—which was once estimated to be the second most distant object in the Solar System—are extremely far away, so it's difficult to determine its exact size with absolute certainty.

Originally Brown and his team estimated 2007 OR10's diameter to be approximately 745 miles (1200 kilometers), which puts it smaller than the Kuiper Belt's other dwarf planets: Pluto, Eris, Haumea and Makemake. However, a new team led by András Pál of the Konkoly Observatory in Budapest, Hungary estimates 2007 OR10's diameter to be 955 miles (1535 kilometers).

To more accurately measure its diameter, Pál and his team relied on data from two different space observatories: Kepler and Herschel.

On the heels of its largest planet haul yet, and after several brushes with death, the Kepler team is excited by the quality of science coming not only from this telescopic partnership, but from Kepler itself. Originally designed to determine the number of Earth-like planets in the cosmos, Kepler recently was given new life and a new mission. As part of Kepler's K2 mission, the planet-hunter is turning its sights on a myriad of cosmic objects. In this case, the mysterious 2007 OR10.

"K2 has made yet another important contribution in revising the size estimate of 2007 OR10. But what's really powerful is how combining K2 and Herschel data yields such a wealth of information about the object's physical properties," Geert Barentsen, Kepler/K2 research scientist at NASA's Ames Research Center in Moffett Field, California said in a statement.

According to the new measurements, 2007 OR10 is approximately 155 miles (250 kilometers) larger than previously thought. What does this mean? Well, the larger size implies higher gravity and it means the surface is much darker than we thought. In fact, 2007 OR10 is darker than most of the other dwarf planets. Astronomers are attributing this to the fact that its surface may be covered in methane ices, giving it a ruddy hue.

"Our revised larger size for 2007 OR10 makes it increasingly likely the planet is covered in volatile ices of methane, carbon monoxide and nitrogen, which would be easily lost to space by a smaller object," lead researcher András Pál, of Konkoly Observatory in Budapest, Hungary, said in a NASA press release. "It's thrilling to tease out details like this about a distant, new world—especially since it has such an exceptionally dark and reddish surface for its size."

So when will 2007 OR10 get a proper name? That is up to the discovery team. In the past they haven't known enough about this icy world to give it a fitting name. Perhaps now they can.