Nearly four years ago, during the Ph.D. thesis research of my former graduate student Meg Schwamb, we discovered a distant bright Kuiper belt object. Our hope had been that something so distant would be like Sedna – far away, but part of an even more distant population. But it wasn’t. The object was more like Eris – far away, but on its way back in. The object got an official license plate number, based on the date of discovery: 2007 OR10.
Back then, I was surprised to have found something so bright so far away. It’s true that Eris is even brighter, but partially it is so bright because it is covered in icy frost that reflects almost all of its sunlight. 2007 OR10 didn’t seem big enough to have enough of a gravitational pull to hold onto enough gasses to have a frosty surface. So why should it be so bright?
We know that the icy outer parts of the dwarf planet Haumea were blasted into space 4 billion years ago, and we have even found some of these left over pieces. When we find them, they are incredibly bright, not because they have frosts held on by gravity, but because they are essentially pure chunks of water ice with no dark contamination on the outside.
What if 2007 OR10 were one of these pieces?
The idea that 2007 OR10 could be a chunk left over from Haumea was a little crazy. After all, 2007 OR10 and Haumea were no even vaguely close to each other, while all of the other pieces that we had found were packed tightly into the same region of orbital space. But I knew that some orbits very near Haumea’s pieces were unstable. If 2007 OR10 had happened to land in such an unstable region right after collision, it could have found itself flung out to its current distant orbit.
Sometimes you don’t have enough evidence to prove a hypothesis and you just have to take a leap of faith. The idea just somehow made sense of a lot of disparate observations. It had that feel of correctness to it. I liked the idea so much that when it came time to give 2007 OR10 a nickname, we named it Snow White, with the assumption that it would have a nice bright white icy surface like all of those other pieces of Haumea. (I was clearly heavily influenced by the most popular movie in my house at that time when Lilah was 3 years old. It’s actually surprising that I didn’t immediately recognize that 2007 OR10 was so far away exploring the outer parts of the Kuiper belt that I should have nicknamed it Dora.)
It was a leap, but at least one that we could eventually prove, if it was indeed true. All we needed was to determine the surface composition of Snow White, see that it looked like pure water ice, and then announce success. And as an even easier first step, all we needed to do was to measure the color of Snow White. All of the icy pieces of Haumea are, in fact, white, while most everything else in the Kuiper belt has more of a reddish color. It would be quite easy. As soon as we found that it was white we would pretty much know that we were right.