Mike Brown's Planets

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.

Is it real, or is it cat hair?

Seven years ago this week I was preparing one of my favorite lectures for The Formation and Evolution of Planetary Systems, a class I frequently teach at Caltech. “Preparing” is probably the wrong word here, because this lecture, called The Edge of the Solar System, was one I could give even if instantly wakened from a cold deep sleep and immediately put on stage with bright lights in my eyes and an audience of thousands and no coffee anywhere in sight. The lecture explored what was known about the edge of our main planetary system and the ragged belt of debris called the Kuiper belt that quickly faded to empty space not that much beyond Neptune. Conveniently, one of my most active areas of research at that time was trying to figure out precisely why this ragged belt of debris had such an edge to it and why there appeared to be nothing at all beyond that edge. I could wing it. So instead of preparing the lecture, I really spent that morning doing what I did whenever I had a few spare moments: staring at dozens of little postage-stamp cutouts of pictures of the sky that my telescope had taken the night before and my computer had flagged as potentially interesting. Interesting, to my computer, and to me, meant that in the middle of the postage stamp was something that was moving across the sky at the right rate to mark it as part of the Kuiper belt. I was not just lecturing about this debris at the edge of the solar system, I was looking for more of it, too.

For most of the past decade the last thing I would do before going to bed was to step out on to my back patio and stare up at the sky for a few minutes, checking for clouds. If the skies were clear I always slept better. In the morning, I would hop out of bed and do the same thing, to see if any unexpected weather front had passed or cirrus had snuck in while I had been sleeping. If all was well with the skies, I knew that my robotic telescope 95 miles southeast of me, likely had a successful night scanning the skies, and I was excited to get up and get to my office to see the results. I knew that any clear night we might (and eventually did!) discover something larger than anything else ever seen past Neptune. It was just a matter of time and of keeping those pesky clouds away.

After writing last week about a pretty major 5 year anniversary – the discovery on Dec 28^th 2004 of what is now called Haumea – it seems funny to be writing once again about a 5 year anniversary. But that’s just the way that reality worked. Eight days after discovering Haumea, and just a few days into the new year of 2005, I was back in my office again. I wanted to be studying Haumea – or Santa, as we called it then – since I was certain that it had to be bigger than Pluto, but, sadly for me, we still didn’t have any new data on it. We only had those first three pictures and there was nothing new to learn. We were scheduled to get more data soon, but not soon enough for sooth my anxiousness. My fingernails were nubs.

Last night, for the second time this decade, I got to have dinner and give a talk on the floor of the dome of the famous 200-inch Hale telescope at Palomar Observatory. It’s rare for anyone to give a talk on the floor of the 200-inch telescope, because Palomar, like every other large telescope around the planet, is used night after night after night looking at everything from the nearest asteroids to the edge of the universe. Few or no pauses are allowed for frivolities such as dinners and talks (in this case we got in, had dinner, gave a talk, and vacated the floor just as the sun was setting). So it was a treat when I got invited to speak to an intimate gathering of supporters of Palomar and Caltech – the university where I work and the one which, not incidentally, owns and operates Palomar – on the floor of the dome. It was even more of a treat because I had been the speaker at the last one of these dinner 8 ½ years ago, and it was particularly interesting to reminisce about what had happened in the almost-decade since then.

When I gave that first talk, in September of 2000, I was a young assistant professor at Caltech who had embarked on what I think it is fair to say was an audacious project: I was going to go find the 10^th planet. I had spent the previous two years systematically scanning a wide swath of sky using the seemingly ancient technology of manually slapping giant glass photographic plates to the back of a wide-field telescope, exposing the photographic plates to the sky for half an hour at a time, developing the photographic plates in the darkroom downstairs, and then looking at repeat exposures of the same patch of the sky to see if – perhaps! – I could find something that had moved. It was exactly what Clyde Tombaugh had done 70 years earlier that had led to the discovery of Pluto, but, no, I had the advantage of a much larger telescope and the use of computers to help analyze the final photographic plates.

At the time of the talk 8 ½ years ago I was in the third year of the project, where I was going back with a larger telescope to try to confirm anything that I thought I had detected during the first two years with the photographic survey. I told my audience sitting under the 200-inch telescope about what I was doing and about what I hoped to find. I told them about photographic technology versus the new digital cameras now widely in use. I told them about why I thought that after this third year I was going to have made that discovery I was hoping for and the 10^th planet would be in our grasp. It was, I daresay, a talk full of exciting promise.

It’s a good thing I wasn’t asked to give a follow up talk right away.

By the following year it was clear that my three year survey had found a grand total of absolutely nothing.

I told that story last night at the 200-inch telescope and everyone chuckled. They chuckled, of course, only because they knew what came in the years that followed. What came next? We scraped the photographic plates, installed experimental digital cameras, roboticized the telescope, and kept scanning and scanning and scanning. With the benefit of the faster and more sensitive digital cameras we slowly surveyed the whole northern sky and blew the outer solar system open.

Last night I showed my baby pictures from the past decade. I showed Quaoar, the first large Kuiper belt object that we found, the one named for the creation force of the local Tongva Native American tribe, the harbinger of larger objects to come. I showed Orcus with its newly named moon Vanth, and talked about its odd mirror-image orbit to Pluto. I showed Sedna, far beyond the Kuiper belt, in an orbit that takes 12,000 years to go around the sun, named for the frigid Inuit goddess of the sea, a beacon pulling us even further in the distant solar system. I showed Haumea, with her two moons Hi’iiaka and Namaka, spinning her was across the sky, I showed lonely Makemake, bird god of the Rapa Nui, the runt of the litter that produced the Big Three of Makemake, Pluto, and Eris. And then, of course, I showed Eris her, in all of her discord and strife, with her tiny moon Dysnomia circling her.

I really do feel like each one of these is like a child to me. And, like children, whenever the rest of them are not in the room, I will secretly tell you that this one is my favorite. They’re all my favorites. I can tell you stories about their little quirks, their odd habits, and a funny thing that this one did the other day when it thought no one was watching (did you know that the night before Namaka went right behind Haumea playing a little hide-and-seek with us? Silly little moon.).

Something else was particularly interesting to me about my talk 8 ½ years ago at Palomar. Something happened that day that I am certain I will never forget. I was inside the telescope waiting for the group of Caltech supporters to arrive, and finally hearing the knock on the outside door, I opened the door, and, as my eyes adjusted to the blinding outside light, I was greeted by the director of the group of Caltech supporters. She had worked on the Caltech campus for years, but somehow our paths had never crossed. I had certainly never seen her before. How do I know for sure -- you might ask. Trust me -- is my answer. I would have remembered. She walked in the door, and I fumbled my words introducing myself. Her name was Diane Binney.

Diane Binney doesn’t work at Caltech anymore, but she came on the trip to Palomar last night anyway. It was her first time back to the mountain since that time 8 ½ years ago when I gave a talk up there. She came to see old friends and revisit old places. And, since she hadn’t seen many of the people in a long time, she brought baby pictures of her own. She has a 3 ½ year old daughter named Lilah. Lilah has Diane’s last name as a middle name, but she gets the last name from her father. Me. Lilah Binney Brown.

It’s true. A year ago the loss of that much money would be front page of every newspaper, instead of buried inside of an analysis in the business section. We were all getting used to such numbers that only hundreds of billions – or perhaps trillions – matter much anymore.

It reminds me a lot of the Kuiper belt.

Almost seven years ago we discovered our first truly large object in the Kuiper belt. It was given the license plate number of 2002 LM60, but we quickly named it Quaoar, after the creation force of the Tongva Native American tribe indigenous to the Los Angeles basin, in homage to the fact that the discovery was made by us right here in the Los Angeles basin. Quaoar made the front page of most major newspapers (except, amusingly, the Los Angeles Times).

At the time of the announcement of the discovery, the most important thing that we knew about Quaoar was that it was about half the size of Pluto. It was thus likely bigger than anything that had been found in the solar system in the past 72 years. The main part of the story that newspapers honed in on was, of course, whether or not Pluto should actually be called a planet. My very favorite quote, published in the Birmingham, Alabama newpaper, quotes me saying “Quaoar is a big icy nail in the coffin of Pluto as a planet.” Pretty good quip, I thought.

The hunt continued.

The next year we announced the discovery of Sedna, both larger than Quaoar and on a distant elongated orbit that made it more distant than anything else that we had ever found. Explaining that odd orbit has been a task I have been trying to continue to this day. I still don’t know the answer, but the mystery made the front cover of Discover magazine.

The hunt continued.

A year later we hit the jackpot, with the discoveries of Haumea, Eris, and Makemake. With Eris being larger than Pluto and eventually providing the silver bullet into the heart of Pluto’s planethood, it received a lot of attention.

The hunt continued.

After some time we started all over again, looking specifically for really super distant things like Sedna. We found a lot of things, but only one thing really far away. It wasn’t as far as Sedna, or even as far as Eris, but it was indeed the third most distant thing we had ever seen.

By now we understood the distant Kuiper belt to know that, basically, we should never see it. The only reason we ever see things is when they are brighter – or more reflective – than they are supposed to be. The only reason that things are more reflective than they are supposed to be is that they are big. The only thing that made sense is that this new thing we had found was big and reflective.

We nicknamed it Snow White.

The survey that found Snow White was specifically looking for quite distant things like Sedna; things that would help us better understand the beginning of the solar system. Snow White, we finally learned, was not like Sedna at all. It was just a normal Kuiper belt object found slightly far away. Bigger than most, but otherwise, as far as we knew, unremarkable.

What to do?

Our normal policy is to delay the announcement of particularly interesting Kuiper belt objects until we have prepared a full scientific paper on them. Snow white perhaps deserved the same treatment. It is big; big is inherently interesting. But… we had nothing interesting to say about this one. It has a typical Kuiper belt object orbit. Its reflectance spectrum shows nothing particularly unusual.

It’s just a big Kuiper belt object. Perhaps even the 5^th largest one known. It probably fits between Sedna and Quaoar in size. A few years ago it would have been front page news. Now? Yawn. Nothing.

A few people have written me asking why the press has been so unkind as to ignore Snow White. But don’t blame the press. Just blame me. We didn’t even write a press release to warn the press that there was anything interesting to write about. Because, in the end, I couldn’t think of anything interesting to write about.

It’s just a big Kuiper belt object. I don’t think that it individually tells us anything particularly new about the outer solar system. Quaoar was a good signal that Pluto’s demise would come soon; Sedna was a sign of an entirely unknown distant population; Haumea and Makemake and Eris were each scientifically rich in the things they taught us about what it is like to be a tiny icy body.

Snow white? Well, it’s just a big Kuiper belt object.

Someday we’ll learn more. Perhaps it will have a moon. Perhaps our quick look at surface composition overlooked something particularly interesting. If so, we’ll be ready with a bail out: prepare a full scientific paper, maybe even tell the press this time and use the opportunity to educate the public, once again, about what is fun and interesting out there at the edge of the solar system.