Mike Brown's Planets

(don't forget to read Part 1 and Part 2)

Snow White’s chance for redemption finally came last year.  I got an email from Adam Burgasser, an astronomer at UC San Diego, best known for his studies of brown dwarfs in the local universe (less well known, but perhaps more relevant in this case, is that I was his Ph.D. advisor a decade ago). Adam had just moved from MIT where he had helped design a new instrument for the Magellan telescope in Chile – the FIRE spectrograph -- perfectly suited for studying brown dwarfs. An instrument perfectly suited for studying brown dwarf turns out, by coincidence, to also be ideal for studying the surfaces of objects in the Kuiper belt. Adam wanted to take this new instrument on a quick test drive on something interesting in the outer solar system. He emailed me asking if there were any bright objects in the Kuiper belt worth observing. My instant response: YES!

One of the nicest things about science is that, usually, when you’re wrong  you’re just wrong.  There is no use sitting around arguing about it or trying to persuade someone to change his mind, you’re just plain wrong and the universe has explained it to you. Game over. Thanks for playing. Try again later. Next?

Only there really was no “next.” Red? For the most part, colors of objects in the Kuiper belt are relatively mysterious, so there wasn’t much of story there. Snow White remained nicknamed Snow White, despite the now obvious inappropriateness of the name, but it mostly became known as a moderately large object in the Kuiper belt that didn’t have a real name. As I mused in this space 2 1/2  years ago, Snow White needed a bailout. By which I meant, we needed to find out something interesting about it or it was never going to be worth talking about, much less naming. As I said back then, "Snow white? Well, it’s just a big Kuiper belt object."

And then something really interesting happened: Snow White got brighter.  While observing a slew of Kuiper belt objects at the Keck observatory two years ago, we swung the telescope around to Snow White and were shocked to find out that it was almost two times brighter than we had expected.

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?

I had a theory.

In part 1 of this story I told about the discovery of Sedna, the first – and still only – body found far beyond the edge of the Kuiper belt. Part 2 described some of our early theories on how Sedna had gotten there and what it was telling us about the early history of the solar system. Here I’ll begin talking about the most recent searches for more things like Sedna and how we’re doing so far.

Seven years ago, I knew with certainty that the discovery of Sedna in a strange orbit that never brought it close to any planet was telling us something profound about our solar system. I also knew that Sedna would never divulge her secrets alone. To learn more, we’d have to find more things like Sedna.