How I Killed Pluto and Why It Had It Coming - Mike Brown (2010)


Keeping Pluto dead has taken a lot of work.

In the days, months, and years since the decision was made, I’ve been accosted on the street, cornered on airplanes, harangued by e-mail, with everyone wanting to know: Why did poor Pluto have to get the boot? What did Pluto ever do to you?

It is at these moments that I am most happy that astronomers ignored my initial advice to simply keep Pluto and add Xena and forget about a scientific definition. I am thrilled that astronomers instead chose to put a scientific foundation behind what most people think they mean when they say the word planet. They don’t mean “everything the size of Pluto and larger,” and they certainly don’t mean “everything round.” Instead, when people say “planet,” they mean, I believe, “one of a small number of large important things in our solar system.”

My job is just to explain the solar system as it actually is. People, I think, will then realize themselves that Pluto is not one of these large important things in our solar system.

Here is what I say to people:

Many astronomers, tired of the endless debates before and after the demotion of Pluto, will tell you that, in the end, none of this matters. Whether Pluto is a planet or not is simply a question of semantics. Definitions like this are unimportant, they will say. I, however, will tell you the opposite. The debate about whether or not Pluto is a planet is critical to our understanding of the solar system. It is not semantics. It is fundamental classification.

Classification is one of the first processes in understanding something scientifically. Whenever scientists are confronted with a new set of phenomena, they will inevitably, even subconsciously, begin to classify. As more and more things are discovered, the classifications will then be modified or revised or even discarded to better fit what is being observed and what they are trying to understand. Classification is the way that we take the infinite variability of the natural world and break it down into smaller chunks that we can ultimately understand.

So how should we classify the solar system? It’s hard, because we are sitting in the middle of it and have known planets our whole lives. But let’s try to do it from the perspective of someone who has never seen a planet before. Imagine that you are an alien who has lived your whole life on a spaceship traveling from a distant star to the sun. You don’t know that planets exist. You don’t even have a word for planet in your language. All you know is your spaceship and the stars you can see surrounding you. The sun—which originally looked like any other star—now gets brighter and brighter as your destination nears.

As you start to stare at and wonder about the sun, you suddenly notice that—wait!—the sun is not alone! You see that there is something tiny right next to it. You’re excited beyond alien words. As your spaceship gets closer and you look even more carefully, you suddenly realize there are two tiny things next to the sun. No, three. No, four!

You have just found the things that we call Jupiter, Saturn, Uranus, and Neptune: the giant planets. From your perspective, still quite far from the solar system, they look tiny and so close to the sun as to be barely distinguishable. You don’t have a word to describe them, so you make one up in your alien language: Itgsan.

You keep looking for a fifth Itgsan out beyond that fourth one you found, because it seems logical that there should be more, but even as your spaceship gets closer and closer to the system, you don’t see anything out there. Trust me, I understand your disappointment.

Finally, as you get close and the four Itgsan get brighter and appear more distinguishable from the sun, you realize you were looking in the wrong place all along. There are other things next to the sun, but they are inside the first Itgsan, not outside. There are four of them, but they’re much smaller than the first four things you found. So you come up with a new word. You call them Itrrarestles. You don’t know it, but you’ve just found Mercury, Venus, Earth, and Mars.

For a very long time, as you keep getting closer, there is nothing new. Finally, when you’re almost on top of the solar system, you realize that between the small Itrrarestles and the large Itgsan there is a band of millions and millions of tiny things going around the sun. And looking even more carefully, you see that outside the large Itgsan there is another band with even more. You call them something that I can’t pronounce, but I call them the asteroid belt and the Kuiper belt.

Nowhere in that alien brain of yours would it be likely to occur to you to take one or two or even a few hundred of the things sitting in the Kuiper belt or in the asteroid belt and put them in the same category as the big things, the Itgsan and the Itrrarestles. Instead, you would quite rationally declare that the solar system was best classified by four major categories. And you would, I think, be correct.

The only thing wrong with our current classification of the solar system as a collection of eight planets and then a swarm of asteroids and a swarm of Kuiper belt objects is that it ignores the fundamental distinction between the terrestrial planets—Mercury, Venus, Earth, Mars—and the giant planets—Jupiter, Saturn, Uranus, Neptune. In the class on the formation of planetary systems that I teach at Caltech, I try to convince my students that, really, there are only four planets and that Mercury, Venus, Earth, and Mars shouldn’t count. But even students who worry about their grades aren’t willing to go that far. So, even though the aliens call them Itgsan and Itrrarestles, we’ll lump them together and just call them all Tsapeln.

You can classify anything at all in many different possible ways. If you are studying birds, you might split them into land birds and seabirds; carnivorous birds and seedeaters; red birds, yellow birds, black birds, and brown birds. All of these distinctions can be important to you, depending on what it is you are studying about birds. If you are studying their mating habits, you might classify them in categories of monogamous and polygamous. If seasonal migration is your thing, you could classify them by those that stay put and those that fly south for the winter.

Things in the solar system can equally well be categorized in many different ways. Things with atmospheres. Things with moons. Things with life. Things with liquids. Things that are big. Things that are small. Things that are bright enough to see in the sky. Things that are so far away that only the biggest telescopes will ever see them. All of these are perfectly valid categories, and they might be of utmost importance to you if you study one specialized type of thing about the solar system. As with birds, your favorite solar system classification will depend on your interests.

Most people, though, don’t have specialized interests in the solar system. The only classification scheme they will ever know is the word planet. They will know what a planet is and how many planets there are and what their names are. Their entire mental picture of what the solar system is, of how our local bit of the universe is put together, will be carried in the understanding of that simple word. The definition of the word planet, then, had better carry with it the most profound description of the solar system possible in a single word.

If you think of the solar system as a place consisting of eight planets—or, better, four terrestrial planets and four giant planets—and then a swarm of asteroids and a swarm of Kuiper belt objects, you have a profound description of the local universe around us. Understanding how such a solar system came to be is one of the major tasks of a wide range of modern astronomers. If, on the other hand, you think of the solar system as a place with large things that are round and smaller things that are not quite round, you have a relatively trivial description of the universe around us. There is nothing important to study here: We’ve known for hundreds of years that gravity pulls big things in space into the shape of a sphere.

•   •   •

Sometimes you don’t even have to go through such extensive arguments. If you catch a person early enough, before the idea that Pluto deserves to be a planet has sunk in, you can teach things correctly from the start. Take Lilah, for example. Everywhere I went in the months following the IAU decision, people wanted to know if I thought Pluto had been treated fairly. Did I think Pluto was a planet? After a few weeks, I taught Lilah to answer for me.

“Lilah, is Pluto a planet?” I would ask, beginning our choreographed banter.

She would frown and shake her head.

“No no no no no no no.”

As she got older the banter continued: “So what is Pluto, Lilah?”

“He’s not a real dog. He’s a dwarf dog.”

My friends would laugh, and then invariably go out and buy Lilah Pluto toys. She has stuffed dogs, of course, but also a collection of nine-planet memorabilia. Early on she learned to figure out which one of the nine little circles on whatever picture she had was Pluto and then promptly declare, “Pluto is a dwarf dog.” The continued laughs from that line were more reinforcement than I could possibly have given.

Another friend was worried how Lilah would react when she got older and discovered that I was a planet killer. “What will Lilah think,” the friend said, “when she learns that Pluto is not a planet and that you are to blame?”

“I know what’s going to happen,” I replied. “In second grade or third grade, when she learns about planets she’ll come home and say, ‘Daddy, today we learned about the eight planets,’ and I’ll say, ‘Lilah, did you know that when you were born we thought there were nine or even ten planets?’ She’ll look at me, shake her head, and say, ‘You know, adults are so stupid.’ ”

•   •   •

Now that Xena, too, was officially called a dwarf planet, it finally got a real name. The possibilities were wide open, but Chad, David, and I had decided that because—at least in our minds—Xena had been the tenth planet in good standing for an entire year, we wanted to give it a Greek or Roman name, like all of the other planets have. The problem was that there were very few left to go around. Back in the 1800s, when asteroids were first being discovered, they were, of course, called planets. And people wanted them to have Greek or Roman names, like the other planets. So they used up almost all of the major gods and goddesses and most of the minor ones, too. Every time we found a name we thought might be nice, we had to look it up in the databases of asteroid names to see if it had been used. Usually it had been. Finally, David wrote a quick computer program to correlate all asteroids with all names of Greek and Roman gods so we could see what—if anything—was left.

There wasn’t much, and what there was was hardly recognizable. Obscure demigods of long-forgotten activities. Minor protectors of long-gone professions. But one name grabbed my attention. I remembered this name from my high school mythology readings, and I couldn’t believe no one had used it before. Here was a major goddess with a fascinating backstory, overlooked in the solar system for two centuries. I quickly double-checked all of the asteroid databases. I double-checked that my mythological memory was correct. And then I sat down and wondered, for the first time since I had correctly predicted my sister’s pregnancy, whether or not there was some sort of cosmic force governing the stars and planets and even the dwarf planets after all. Maybe there was some sort of fate that had kept this name free until now, the perfect time for it to be unveiled. Maybe there was no free will in any of this. That idea is, of course, crazy, but it’s hard not to think crazy thoughts now and then.

I quickly e-mailed Chad and David, and we all agreed: the largest dwarf planet, temporarily nicknamed Xena, cause of the largest astronomical showdown in generations and the killer of Pluto, would henceforth be called Eris, after the Greek goddess of discord and strife.

I love the myth of Eris. As a perpetrator of discord and strife, she was not everyone’s favorite goddess to have around, so when the human Peleus and the sea nymph Thetis decided to wed, they didn’t invite her to the wedding. I understand their dilemma. Having gotten married myself, I know that there are always touchy issues involving the invite list. There are A lists and B lists and whole categories where you think, “Well, if I invite one person from this category, I should really invite everyone from this category,” and then the bar tab gets out of control. If you find yourself having a wedding and are trying to decide whether or not to invite the goddess of discord and strife, my only recommendation to you is that if you decide not to invite her, make sure that she is not the only goddess who is not invited, which was the mistake Peleus and Thetis made.

The goddess of discord and strife doesn’t take snubs lightly. She crashed the wedding anyway, and to cause, well, discord and strife, amid the guests she rolled in a golden apple on which she had inscribed “Kallisti,” meaning “to the fairest.” As Eris had planned, all of the goddesses at the wedding got into a fight over who was the fairest and most deserving of the apple. They asked Zeus to decide. But Zeus, being no dummy, took the rather dim-witted mortal Paris, put him on the throne, and asked him to decide. The goddesses, being no dummies either, knew that they had best resort to bribery. Hera offered Paris domination over men. Athena offered Paris victory in battle. Aphrodite offered the love of the most beautiful woman in the world. Paris didn’t have to think twice about that one and promptly handed Aphrodite the golden apple. Aphrodite then mentioned the fine print: The most beautiful woman in the world now did indeed love him, but she was married and living in Greece, and the Trojan Paris would have to go abduct her. He did, but the other Greeks didn’t take it well. The decadelong Trojan War ensued.

I was sold, but I still had to name the moon of Eris. Gabrielle had been the obvious counterpart to Xena, but who went with Eris? I read through all of the literary mentions of Eris from the past. I pondered geographical considerations. I looked at family ties. I was in search of something very specific; I had a plan that I had told nobody. Again, fate intervened, and I found precisely what I was looking for. I sent the proposed name of the moon to the IAU, and I told no one.

At home that night, I told Diane all about Eris. She thought it was a fabulous name. “What about the moon?” she asked.

“It’s a surprise,” I said. “A surprise for you.”

When the name Eris was announced in the press a few weeks later, many people who had been following closely got what they took to be the inside joke on the name of the moon. I had called the moon Dysnomia. Dysnomia was one of the children of Eris, and she was the daemon spirit of lawlessness. Xena on TV had been played by Lucy Lawless. People assumed that Dysnomia was a sly nod to that original nickname.

I was happy to take credit for the wordplay, but in reality it was an accident that I hadn’t even noticed until someone pointed it out to me. I’ll just chalk that up, once again, to cosmic fate.

On the day that the names were announced, I couldn’t wait to get home to tell Diane.

“I named the moon for you,” I told her.

“You named the moon Diane?” she asked.

I explained that since the name Diane had long ago been taken by an obscure asteroid, I had had to be subtle. When Jim Christy discovered Pluto’s moon, he took the first syllable of Charlene—his wife’s name—and made a name out of it that’s found in mythology: Charon. In searching for the perfect name for Eris’s moon, I had looked for one that had the first syllable of Diane. Dysnomia is, admittedly, a bit clunkier than Charon, but there, in the first syllable, is my wife, Diane, whose family frequently calls her Di.

“Dysnomia is named for you,” I said. “It’s my present forever.”

“Um, thanks, I think,” said Diane.

After some contemplation, she added, “This doesn’t excuse you from Christmas presents, you know.”

A year earlier, when the existence of Xena was first announced, I had considered naming the potentially tenth planet after Lilah in some way. Diane had dissuaded me.

“What if we have a second child and you never find another planet?” she said.

That was a convincing argument.

I told her she should take the moon naming as a good sign: While it was possible that we might had a second child, there would be only one wife!

“Um, thanks, I think,” said Diane, again.

•   •   •

Many people know about the Rose Parade, which winds through Pasadena every New Year’s Day just as it did four days before the discovery of Eris in 2005. Less well known is the yearly alternative version of the Rose Parade called the Doo Dah Parade, which goes along some of the same main parade route as the Rose Parade. It attracts large crowds and features things such as marching toilets, a Doo Dah Queen (usually in drag), flying tortillas, and a Precision Grill team, cooking up barbecue along the way. In 2006, it also featured a New Orleans Jazz Funeral for Pluto organized by some local astronomers with a sense of humor. The eight planets were each represented by a costumed astronomer with a large cardboard name tag hanging around his or her neck. They carried Pluto in a casket to sounds of New Orleans jazz. The astronomers invited me to participate and gave me a cardboard name tag that read: “Mike Brown: Pluto Killer.” I had agreed to march in the parade on one condition: that Eris also be invited. Eris, played by Lilah, was pushed in a stroller down the parade route by her father.

Like most marchers in the Doo Dah Parade, we got quizzical looks, a few claps, a smattering of boos, and a lot of tortillas thrown at us. I spent most of my time trying to make sure Lilah didn’t pick them up and eat them. But still, Pluto was dead, and it was good to participate in its burial.

•   •   •

But not everyone was ready to bury Pluto just yet.

On the very day of the vote to demote Pluto and Eris, a few astronomers began collecting signatures protesting the details of the IAU decision. They issued a simple statement:

We, as planetary scientists and astronomers, do not agree with the IAU’s definition of a planet, nor will we use it. A better definition is needed.

It’s hard to argue with that statement. As much as I am proud of the astronomers who had the guts to go against emotional sentiment and to remake the solar system correctly, the actual definition by which they did it is pretty clunky. In fact, I won’t use it, either.

In the question-and-answer session of a recent talk I gave at Sarah Lawrence College, a very agitated young woman raised her hand and began to read from notes: “In the IAU definition of the word ‘planet’ it says you have to be three things to be a planet …”

“Wait, wait, wait,” I said. “Before you even start, let me tell you why you should never think about the IAU definition of the word ‘planet.’ ”

In the entire field of astronomy, there is no word other than planet that has a precise, lawyerly definition, in which certain criteria are specifically enumerated. Why does planet have such a definition but star, galaxy, and giant molecular cloud do not? Because in astronomy, as in most sciences, scientists work by concepts rather than by definitions. The concept of a star is clear; a star is a collection of gas with fusion reactions in the interior giving off energy. A galaxy is a large, bound collection of stars. A giant molecular cloud is a giant cloud of molecules. The concept of a planet—in the eight-planet solar system—is equally simple to state. A planet is one of a small number of bodies that dominates a planetary system. That is a concept, not a definition. How would you write that down in a precise definition?

I wouldn’t. Once you write down a definition with lawyerly precision, you get the lawyers involved in deciding whether or not your objects are planets. Astronomers work in concepts. We rarely call in the attorneys for adjudication.

The young woman in the audience was not satisfied.

“You can’t just dismiss the definition. The definition is the reason that Pluto is no longer a planet!”

I tried to explain to her that the concept, not the definition, is the reason that Pluto is not a planet. The definition was simply a poor attempt at codifying the concept.

She went on: “But by part three of the definition even Jupiter is not a planet!”

The young woman could probably make a reasonable case in court for her strict reading of the definition. But when the case was appealed to the Supreme Court—and it certainly would be—some justices might try to discern the original intent of the definers. I am certain that it was not anyone’s intent to exclude Jupiter from being a planet. The original intent was simply an attempt to describe the eight-planet solar system. The case for a strict reading of the definition would ultimately be tossed out. And then, if the justices were wise, they would also toss out the definition altogether. We’re better off without one. Pluto is not a planet not because it fails to meet the three-headed criteria laid out by the IAU. Pluto is not a planet because the criteria were written to try to explain the concept that Pluto is not a planet.

•   •   •

But the astronomers who organized the petition saying that they would never use the IAU definition were not quibbling over the logic of having a definition in the first place. They wanted the eight-planet solar system overturned. They wanted Pluto resurrected. While most of the rest of the astronomical world has acknowledged the reasonableness of the decision and moved on, a small group is continuing to try to have Pluto make a comeback.

Over the months and years, their arguments have changed, in the attempt to get some traction. At first, they took a line straight from the people trying to get creationism taught alongside evolution in schools: “Teach the controversy!” they said. Then they argued that the IAU decision was undemocratic because many of the members of the IAU had not been there that day to vote. The complaint is true, but the implication that the outcome would have been different is quite a stretch. Sometimes the argument is that only planetary astronomers are qualified to make the decision—again, as if that would make a difference. In my unscientific poll of seven professors of planetary science who happen to work on the same floor as I do, all seven thought that eight planets make the most sense.

Particularly amusing to me was the complaint about the phrase dwarf planet. By the simple rules of grammar, a dwarf planet is a planet, they would say. The fact that the IAU would say that a dwarf planet is not a planet demonstrates that the entire decision must be wrong. What no one making these arguments remembers—or admits to remembering—is that the only people who liked the phrase dwarf planet at first were the ones who hoped that it would save Pluto when the other planets were renamed “classical planets.” Yet Resolution 5B was a specific vote on this issue, and it clearly stated that dwarf planets are not planets—just as Matchbox cars are not cars, stuffed animals are not animals, and chocolate bunnies are not bunnies. I don’t particularly like the phrase dwarf planet, either, but it is serviceable.

I’ve heard the argument that the definition is unworkable because it is inconsistent with the rest of astronomy. Nowhere else in astronomy, some say, do you classify an object by its relationship to its neighbors instead of by its own individual properties. Therefore the only definition that makes sense is that all round things are planets, regardless of where they find themselves. Well, not all round things are planets, just round things that orbit stars. And what if the round thing orbits another round thing? Well, then it is a moon, of course. But but but, doesn’t that violate the rule that things aren’t defined in relationship to other things? Well, yes, but that’s just common sense, they would say. Okay. Got it.

•   •   •

A few weeks after Xena became Eris, I received a note from a friend:

The Spanish are trying to steal Santa again.

The Spanish? I hadn’t thought much about them in the preceeding eighteen months and certainly hadn’t heard anything from them. By this time, I was almost able to laugh about the whole incident.

But they were really back.

After the IAU decided to call round things dwarf planets, Easterbunny and Santa were eligible for real names, too, and the Spanish astronomers quickly submitted a name for Santa—because, of course, the discoverers get to name their discovery.

Rumor had it that the IAU was going to act swiftly, so Chad, David, and I quickly consulted and came up with our own name: Haumea, after the Hawaiian goddess of childbirth. Like the name Eris, the name Haumea seemed almost custom made for this object. The goddess Haumea gave birth to her many children by breaking them off from parts of her body. Santa the dwarf planet also had many children throughout the solar system that had broken off from its body. It seemed a perfect fit. And whatever the name was, it definitely should not be whatever the Spanish astronomers were submitting!

I wrote an impassioned letter to the various committees of the IAU proposing the name Haumea and also proposing names for two moons: Hi’iaka, the patron goddess of the Big Island, and Namaka, a water spirit, both daughters of Haumea. In the letter, I laid out—once again—all that had transpired. And then I explained why it was important that the IAU choose wisely which name to use. There was no question that eighteen months earlier someone had done something unseemly. If the Spanish astronomers had fraudulently claimed discovery of something that they had never actually discovered, it would be appropriate for the IAU to condemn such a thing. If, on the other hand, their discovery was legitimate, they should be exonerated and I should be censured for making a spectacularly damaging wrongful accusation. Through choosing a name, the IAU would be officially choosing a side. I thought that the members of the IAU would not want to take sides and would instead pick a name themselves. I urged them not to cop out. No one else had the authority to render any type of meaningful verdict.

I sent in my letter and waited to see what would happen.

And I waited.

Lilah’s second birthday came around.

And I waited.

Lilah’s third birthday came around.

I was hoping that the IAU was taking its job quite seriously and had launched a multiyear investigation into what had happened. Apparently not. My inside sources tell me that nothing happened that entire time. Finally I got a tip that making a decision about Santa was just too hard and that perhaps we should try giving a name to Easterbunny as a way of getting things restarted.

Ah, Easterbunny. I had been thinking about it now for years. The names Sedna and Orcus (another large Kuiper belt object that we had turned up) had fit the characteristics of the objects’ orbits, and the names Eris and Haumea had practically fallen out of the sky at us. Even Quaoar, we felt, was a nice tribute to local mythology.

But what about Easterbunny? Unlike Santa, which has so many interesting characteristics that there were many possible names, Easterbunny has no obvious hook. Its surface is covered with large amounts of almost pure methane ice, a consequence of the fact that it is just a little smaller than Pluto and lacks enough gravity to hold a substantial nitrogen atmosphere, which is scientifically fascinating and all (really, it is) but not easily relatable to terrestrial mythology. For a while I was working on coming up with a name related to the oracles at Delphi: Some people interpret the reported trancelike state of the oracles to be related to natural gas (methane) seeping out of the earth there. After some thought, I decided this theme was just dumb. Strike one.

I spent some time considering Easter- and equinox-related myths, as a tribute to the time of discovery. I was quite excited to learn about the pagan Eostre (or Oestre, or Oster, or many other spellings) after whom Easter is named, until I later realized that this mythology is perhaps itself mythological and, more important, that an asteroid had already been named after this goddess hundreds of years ago. Strike two.

Finally, in mythological desperation, I considered rabbit gods, of which there are many. Native American lore is full of hares, but they usually have names such as Hare or, better, Big Rabbit. I considered Manabozho, an Algonquin rabbit trickster god, but I must admit, perhaps superficially, that the “bozo” part at the end was a turnoff. There are many other names of rabbit gods, but the names just didn’t speak to me. Strike three.

These initial attempts had all happened long ago, and I had given up, figuring I would wait for the IAU decision on Santa. But now, with some prodding, I got back to work.

Suddenly, it dawned on me: There was a potentially interesting small island in the South Pacific that I hadn’t looked into before. I wasn’t familiar with the mythology of the island, so I had to look it up, and I found Makemake (pronounced Hawaiian style as “mah-kay mah-kay”), the chief god, the creator of humanity, and the god of fertility. I had discovered Easterbunny during the time that Diane was pregnant with Lilah. Easterbunny was the last of these discoveries. I have the distinct memory of feeling a fertile abundance pouring out of the entire universe during that time. Easterbunny was part of that. Easterbunny would be Makemake, the fertility god of the island of Rapa Nui.

Rapa Nui was first visited by Europeans on Easter Sunday, 1722, precisely 283 years before the discovery of the Kuiper belt object now known as Makemake. Because of this first visit, the island is known in Spanish (it is a territory of Chile) as Isla de Pascua, but around here, it is far better known by its English name of Easter Island.

•   •   •

The name Makemake was accepted quite quickly and with a modest fanfare by the IAU; as predicted, a decision on Santa was soon rendered, only two years after the initial proposals had been submitted. This time there was no fanfare, no press release, no official pronouncements. The name just appeared on the official IAU list of names one day as Haumea. Three years after the Spanish astronomers either did or did not fraudulently steal our discovery, we were officially vindicated by the IAU, which accepted our name, signaling that we appropriately deserved the credit.

Sort of.

On the IAU’s list, next to the newly added name Haumea, in the space reserved for the name of the discoverers, is a big blank spot. Haumea, unique among all objects in the outer solar system, has no discoverer. It simply exists.

Oddly, though, for an object that no one discovered, it does have place of discovery listed. While the name of the object is Hawaiian, based on a proposal by astronomers from California, Haumea was officially discovered at a small telescope in Spain. By nobody.

What does any of this mean, officially? Mostly, I think, that the IAU didn’t try too hard to figure anything out. Probably the majority of whatever committee was voting thought my version of the story was the most plausible, but there were enough dissenters that a decision was made to soften the pronouncement by listing no discoverer and by backhandedly acknowledging the Spanish claim.

I am disappointed that they made no real effort to figure out what happened, at least as far as I can tell. No one ever asked me anything or requested extra information from me. I suspect the same is true of the Spanish side. In the end, this is as good as it will get. I will never know for sure what actually took place in those two days before the Spanish astronomers announced their discovery.

•   •   •

I still haven’t drunk the celebratory champagne. The friend with whom I made the five-year bet on the foggy night at Palomar Observatory had generously given me a five-day extension, and Eris fit all of the characteristics that she and I had decided a planet must meet. She happily delivered the champagne the next time she was in town. In the end, though, Eris was not the tenth planet; it was instead the killer of the ninth. Champagne doesn’t make a good funeral drink.

Those five champagne bottles sit on my shelf still. I look at them every once in a while and wonder if the time will ever come to pop the corks. I’m still looking for planets, but the bar is now much higher. Anything new that wants to be called a planet needs to be a significant presence in our solar system, and I am not certain that there are any more hiding in the sky. But I keep going. Someday, I hope, I’ll be sitting in my office looking at pictures of the sky from the night before, and there on the screen will be something farther away than I’ve ever seen before, something big, maybe the size of Mars, maybe the size of the earth—something significant. And I’ll know. And, as I did years earlier, I’ll immediately pick up the phone and call Diane. “Guess what?” I’ll say. “I just found the ninth planet.” And—once again—the solar system will never be the same.