How I Killed Pluto and Why It Had It Coming (24 page)

The IAU was quick to act after the discovery of the first objects out beyond Neptune in the Kuiper belt. Things way out are named after creation gods in world mythology, though as the number of objects in the Kuiper belt grew faster than new creation gods, the rule began to be applied more and more loosely. Recently someone even got away with calling something in the Kuiper belt Borasisi, which is a god from a fictional story by Kurt Vonnegut.

For all of its preparedness for endless contingencies and countercontingencies, the IAU had never actually contemplated
a question that was suddenly on everyone’s minds: What do you call something new that is bigger than Pluto? How do you recognize a new planet when you see it?

Like any good international organization, it knew what to do when faced with such emergencies: It needed to form a committee. Better yet, it already had one. At about the same time that Xena was discovered and astronomers (and everyone else) began to try to figure out how small the smallest planet could be, astronomers were also struggling with the question of how big the biggest planet could be. We had it easy in the solar system; it was unlikely that I would ever find anything bigger than Jupiter that needed to be categorized, but discoveries of things larger than Jupiter orbiting around distant stars were beginning to become routine. Some were about as massive as Jupiter or only a little more so. They were clearly planets. Some were only somewhat less massive than the sun. Those were clearly stars. Some were in between. What to do? The IAU formed a committee to decide. This same committee was now charged with figuring out the small end of planets, too.

When the reporters called to talk about the discovery of Xena, they wanted to know where it was, how we had found it, and how big it was. We didn’t yet know the size for sure but thought it could be as much as half again the size of Pluto. And then they asked: When is the IAU going to make a decision about planets?

“I hope they’ll decide before my daughter starts crawling,” I joked when Lilah was three weeks old.

When a bevy of new reporters called after the story about the Spanish snooping broke, they asked what was going to happen to the Spaniards, how the conflict was going to be resolved, and how this might change the way astronomers interacted and protected their data. I explained that many scientists worldwide
suddenly realized that they, too, could be vulnerable to unintended snooping, and many were scrambling to find solutions. And then they asked: When is the IAU going to make a decision about planets?

“I hope they’ll decide before my daughter learns to stand,” I joked a few months later, since Lilah was already crawling by that point.

When we discovered that Xena was not alone at the edge of the solar system, that it had a tiny moon going around it, reporters called again and wanted to know how the moon got there, what it looked like, and what we were planning to call it (Gabrielle, of course, after Xena’s spunky TV sidekick). And then they asked: When is the IAU going to make a decision about planets?

“I hope they’ll decide before my daughter says her first words,” I joked the next winter, since by then Lilah was already standing and taking increasingly assured strolls around the periphery of the room.

In the spring, when we finally were able to use the Hubble Space Telescope to figure out just how big Xena really was, reporters called again and wanted to know what Xena was made of, how it had gotten so big, and how much larger than Pluto it was (only 5 percent, it seemed, which was uncomfortably close to not even being bigger than Pluto at all, particularly when you include approximately 4 percent uncertainty in the measurement). And then they asked: When is the IAU going to make a decision about planets?

“I hope they’ll decide before my daughter goes to college and takes an astronomy class,” I finally reverted to joking when it became clear that no decision was going to be made anytime soon.

People kept asking me when the IAU was going to make a decision because they thought I should know. But I didn’t know
anything. During this entire period, no one officially connected with the decision making—and I didn’t even know who that might be—ever once contacted me to ask a question or to tell me what was going on. I assumed that I was going to wake up one morning, open the
Los Angeles Times
, and see that I was suddenly the official discoverer of a planet. Or that there were only eight planets. Or that I had discovered many planets. Or that I had discovered the only thing in the solar system larger than a planet that wasn’t a planet.

In the face of this uncertainty, I figured it best to be prepared for all options. I called up the person in media relations at Caltech who had—months earlier now—pressed me to decide whether or not to call Xena a planet in that original press release. I told him that we needed to prepare another press release, this time for the IAU decision.

“Great!” he said. “What did they decide to do?”

“Well, actually, they haven’t decided anything yet.”

“But they’re deciding soon, right?”

“Well, actually, I have no way of knowing what they are doing. They might decide tomorrow, and they might decide a decade from now.”

“So …” He paused. “What are we going to say in a press release?”

I knew that I wanted to have the opportunity to tell the full scientific story to the public. I had missed that chance, I felt, back in the original hurried rush when we had to make the announcement right away. I wanted the beauty and subtlety and essential order of the solar system to be at the center of the discussion after a decision was finally made. I cared less what the IAU decided—within limits, of course—than that the science got explained correctly.

“We’re going to write four different press releases,” I explained.

Ten planets made sense if you wanted your planets to have more emotional resonance than scientific significance. We very quickly wrote that press release, hailing Xena as the tenth planet. It made me proud to think of my tenth planet, but even from early on I admit that it also made me feel a little fraudulent. The discovery of Uranus was a big deal, and that of Neptune was amazing. But Xena? Little Xena? The tenth planet? Still: I channeled my inner geologist. If it mattered emotionally, that was all that counted. I was ready.

Scientifically, I agreed much more strongly with our second press release, explaining why there were only eight planets. Eight planets made sense if you were a scientific historian and realized that 150 years ago people had already decided to divide the solar system’s objects into big planets and small asteroids and that Pluto—and now Xena, too—thoroughly fit into the category of the small objects. I liked to think of this one as what people would mean when they said the word
planet
if they really understood the solar system. We hailed the bravery of astronomers for taking a scientifically sound stance in the face of what would certainly be considerable opposition. Even though scientifically I agreed much more strongly with this press release, I was glad we wrote it quickly; it seemed quite clear to me that astronomers would never have the audacity to actually get rid of everyone’s favorite runt planet. Still, to be safe, I thought it best that we have a press release ready. Having the discoverer of the onetime tenth planet agree that it should not be a planet seemed like a powerful line of argument.

Our third press release was for the possibility that the IAU’s decision would be to simply keep nine planets. Keeping Pluto in
the planet club but refusing to allow in bigger newcomers didn’t make sense at all. Yet it did seem like an option that might be on the table, since I had heard a few people say, “Why do we need to change anything when we have nine perfectly good planets?” Our press release said that nine planets was a pretty dumb decision.

The last press release considered a more extreme possibility: that the IAU would stretch the definition of the word
planet
so far that there would suddenly be two hundred planets. A small but extremely vocal group of astronomers had been pushing for a while to thoroughly transform the meaning of the word
planet
. Unlike the ten-planet approach, which was an attempt to understand what people meant when they said the word
planet
, or the eight-planet approach, which was an attempt to discern what people would mean if they had all of their facts straight, or even the nine-planet approach, which was to stick to literally what people meant when they said the word
planet
(the nine planets and nothing else!), the two-hundred-planet approach was an attempt to legislate an entirely new and never before anticipated meaning for the word
planet
. The word was to mean, essentially, “anything in orbit around the sun that is big enough to be round.”

Why round? It is not simply that astronomers are enamored of that particular shape (though, really, why wouldn’t they be?). It is that that particular shape tells us something. If you throw a boulder into space, it will retain whatever irregular shape it originally had. If you throw a hundred boulders into space together, they might stick to one another due to the tiny amount of gravitational pull that each boulder generates, but they could still have almost any shape you might imagine. But if you put enough boulders up into space together, a fantastic thing will happen: The cumulative gravitational pull of all those boulders
will take over. The boulders will pull together and crush and smash one another until you can no longer discern what shapes they had to begin with; instead, they will form a beautiful, simple sphere. Finding something spherical in space indicates that you have found a place where gravity has taken over. I am pretty certain that at no time in the previous several-thousand-year history of the word
planet
did anybody say “planet” and really mean “things that are round due to self-gravity.” It was a new definition by simple fiat. And it would lead to something like two hundred new planets, most of them out in the Kuiper belt.

I explained all of this to the person writing the press releases.

“Why bother writing this one up? It sounds crazy. No one would decide this, would they?”

Well, yes. I actually thought this was the most likely decision that the International Astronomical Union would make—if it was ever going to make a decision at all.

“But why would astronomers do such a crazy thing?” he wanted to know.

Desperation
was all I could answer. Desperation.

As radical as the new definition was, it was the only one on the table that both smelled scientific and also retained Pluto as a planet. I could imagine that it would be hard for a scientific committee to conclude that the definition didn’t need to have a strong scientific basis (the nine- or ten-planet approach). I could imagine that an astronomical committee would be loath to provoke what would certainly be a huge public outcry if it kicked out Pluto (the eight-planet approach). So although the two-hundred-planet approach was the most radical, it had the cover of appearing the most conservative. I could just see it passing.

I didn’t like the definition, but I could live with it. The good news, for me, was that if this new definition was announced, I would have discovered more planets than anyone else in human
history. Not just Xena, Easterbunny, Santa, Sedna, and Quaoar, but dozens more. The bad news was that I couldn’t remember most of their names.

•   •   •

The first anniversary of the discovery of Xena came and went with no hint of what was happening at the IAU. But it was okay. I was busy. Chad and David and I, now joined by some of my students and outside colleagues, wrote scientific papers about the size of Xena, the discovery of Gabrielle (the moon of Xena), the discovery of a thoroughly unexpected second moon of Santa, and the slab of frozen methane covering the surface of Easterbunny; and we still had much, much more to do. There were press releases to develop, talks to give around the country, interviews on TV and radio. But when I think of this time period, I have a hard time remembering almost any of it. What I really remember is Lilah and the moon.

As with any overeducated first-time parents, we were fascinated with understanding Lilah and what she was thinking and doing and understanding. I began reading scientific books on early childhood development, not as a way of pushing Lilah along faster or making sure she was okay, but simply because it was, at the time, the single most fascinating thing I could imagine. I read studies of the development of facial recognition and motor skill control, but what I found the most interesting of all were studies of language development. It seemed so hard for me to imagine that this little baby, being carried around in a bundle in my arms, would someday be sitting in a chair next to me having a conversation.

Diane and I often joke about parents who think that everything their children do is exceptional. Intellectually, we always understood that Lilah would likely be good at some things, not
as good at other things. Exceptional is a pretty high bar. But reading these books about early childhood and watching Lilah develop, I finally understood. She
is
exceptional, because early childhood development is about the most exceptional thing that takes place in the universe. Stars, planets, galaxies, quasars are all incredible and fascinating things, with behaviors and properties that we will be uncovering for years and years, but none of them is as thoroughly astounding as the development of thought, the development of language. Who would
not
believe that their child is exceptional? All children are, compared to the remainder of the silent universe around them.

Emily Schaller, my Ph.D. student, who was always willing to try to engage my obsessions, handed me a book one day on how to teach your baby a primitive type of sign language. The thought was that children are ready to communicate before they have the vocal motor skills for speech. But they can use their hands and arms and fingers to tell you about the world around them.

Lilah’s first sign was, not surprisingly,
cat
(rake two fingers across your face as if to draw whiskers). The two cats—originally Diane’s, now a joint venture—who lived with us barely tolerated the loud newcomer to the house. But they eventually got used to her and realized that she posed no harm, so they would lie close to take advantage of me or Diane being immobilized while holding a sleepy baby and having a free hand available for an ear scratch. Then Lilah learned to roll over. The cats scattered, to eventually return when they realized she was still
mostly
immobile. Then Lilah started to crawl, and that started the years of Lilah chasing after the cats, the cats slinking away, always out of reach. To Lilah, the cats must have been like the end of the rainbow: always in sight, always just out of reach, and gone when you get there. Her first efforts to communicate with the external
world were targeted directly at them. They, sadly, never returned the favor.