How I Killed Pluto and Why It Had It Coming (29 page)

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.