Observations made by NASA’s Kepler space telescope suggest that the icy world known as 2007 OR10 is bigger than astronomers thought –and that’s adding to the pressure to give the probable dwarf planet an official name, nine years after its discovery.
Some of the suggestions pick up on the recent controversy over a British ship-naming contest in which Boaty McBoatface emerged as the overwhelming favorite. So how about Dwarfplanety McDwarfplanetface, or Plutoid McPlutoface?
The cause of all this mirth is a research paper in the Astronomical Journal that provides a new size estimate for 2007 OR10, which lies far out in the Kuiper Belt, the broad ring of icy material just beyond Neptune. The object traces an eccentric orbit that takes 547.51 Earth years to complete, and ranges as far out as 66.9 times Earth’s distance from the sun (6.2 billion miles).
It’s hard to make out the object from that distance. Based on data from the European Space Agency’s Herschel space observatory, scientists had previously estimated its diameter at about 795 miles. But when Kepler’s readings were added in, the estimate rose to 955 miles.
That’s big enough for NASA to make the argument that 2007 OR10 is the third-largest solar system object beyond Neptune, and the solar system’s largest confirmed object without a name. (NASA isn’t counting Planet Nine, a theoretical Neptune-sized object thought to lie beyond the Kuiper Belt.)
When astronomers Meg Schwamb, Mike Brown and David Rabinowitz discovered 2007 OR10, they nicknamed it “Snow White” because they assumed it to be relatively bright. But the new estimate implies that the celestial body is more massive and darker than previously thought.
“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,” study co-author András Pál of Hungary’s Konkoly Observatory said in a NASA news 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.”
The International Astronomical Union has recognized five dwarf planets so far. In order of mean diameter, they’re Pluto, Eris, Haumea (which is an oblong oddball) and Makemake. 2007 OR10 would fit between Eris and Haumea.
To refresh your memory, the IAU defines a dwarf planet as a world that orbits the sun with enough self-gravity to pull itself into a roundish shape, but that has not “cleared the neighborhood around its orbit.” That last point has been the basis for the IAU’s distinction between dwarf planets and honest-to-goodness planets.
So when will 2007 OR10 get its name? That’s up to the discoverers, who have been waiting for astronomers to come up with a better characterization for the object. Snow White and Dwarfy McPlanetface are both out of bounds: According to the IAU’s naming rules, it’ll have to be named after a deity or figure related to creation. For example, Makemake is the Polynesian creator of humanity and god of fertility.
“The names of Pluto-sized bodies each tell a story about the characteristics of their respective objects,” Schwamb said in NASA’s news release. “In the past, we haven’t known enough about 2007 OR10 to give it a name that would do it justice. I think we’re coming to a point where we can give 2007 OR10 its rightful name.”
This week’s report sparked a flurry of tweets about the road ahead for 2007 OR10, including some thoughts from co-discoverer Mike Brown: Here’s a sampling:
— Daniel Fischer (@cosmos4u) May 11, 2016
That said, it definitely is the largest known object without a name. We'll get around to it. Promise. Really. Some day soon. Honest.
— Mike Brown (@plutokiller) May 11, 2016
— James Moore (@QuarkSpin) May 11, 2016
In addition to Pál, the authors of “Large Size and Slow Rotation of the Trans-Neptunian Object (225088) 2007 OR10 Discovered From Herschel and K2 Observations” include Csaba Kiss, Thomas Müller, László Molnár, Róbert Szabó, Gyula Szabó, Krisztián Sárneczky and László Kiss.