A Requiem for Xena

Mike Brown
25 August 2006

Many people around the globe are mourning the loss of Pluto from the pantheon of planets today after astronomers voted overwhelmingly in favor of a definition of the word "planet" that includes only the first 8 planets. The change had been discussed for years, so no one should have been surprised that it finally happened. The new definition essentially corrects an astronomical mistake from 76 years ago, and shows that astronomy can move forward in the face of new information about the solar system. Pluto is now rightly classified with the rest of the recently discovered Kuiper belt objects, rather than awkwardly stuck in with the planets.

I've gotten many phone calls asking for my comments, wanting to hear what I have to say about Pluto. I understand that people are mourning. I understand that people are in pain. Pluto, like all of the planets, is part of our mental landscape of the universe around us. It is a sign post in how we view our neighborhood. We all know a few inviting facts that help to personalize the sign post, even:  the funny tilted orbit, the giant moon, the discovery by a Kansas farm boy. Ripping such a sign post out  feels wrong, like the feeling you got when you were a kid and your best friend across the street moved to another state never to be heard from again. How can it be true?

I don't want to be insensitive to the Plutophiles out there, but enough about Pluto, OK?. I've got my own mourning to do. By the same decision that relegated Pluto to a mere dwarf planet, Xena (aka 2003 UB313), which I discovered 19 months earlier ago, also got the official boot. For the past year it had been mostly known as "the tenth planet" for good reason: it was the largest object found in the solar system in 150 years and was bigger, even, than Pluto itself. This was the discovery that ultimately forced the hand of  astronomers. Either this object was going to have to be called a planet like Pluto or both were going to have to go. When I discovered it and realized that it was, indeed, bigger than Pluto, I immediately called my wife and excitedly told her "I found a planet!"

Right after the astronomical vote yesterday, I made the same phone call again. I had to tell her that the 10th planet was being buried alongside Pluto. Her voice dropped. Really? She said. Really.  My wife was already mourning the little planet that we had gotten to know so well. I think her reaction was like that of the many Pluto fans out there who feel an emotional attachment to Pluto. See, to us Xena was more than just "the tenth planet." We had gotten to know her quite well over the past year. We knew about her tiny moon (Gabrielle, of course), her incredibly shiny surface, and her atmosphere frozen in a thin layer all around the globe. We had discussed her name, her orbit, and how many more like her might be out there. She had become as much a part of our own mental landscapes as Pluto could have been for anyone. In some ways she was like the counter-part to our daughter Lilah, who had been revealed to the world only three weeks before Xena was. All of those memories of the first months of our Lilah's life -- the lack of sleep, the dazed confusion, the incredible happiness -- are tied up with all of those memories of 10th planet craziness -- the rush to learn more, the push to write papers, the quest to get more telescopes pointing that way. And now, just a little after her first birthday, she was gone.

The astronomers did the right thing. Xena is not really gone, of course, she is now actually the largest of the dwarf planets, where she rightfully deserves to be. And now that Xena has a real classification she will even get a real name sometime soon. But my wife and I will still always call her Xena. Lilah may not learn about Xena or whatever the new name will be, in school, but some day we'll tell her that when she was three weeks old the world learned about the 10th planet, and we'll pull out our little box of Xena news clippings and talk about that year when Lilah and the 10th planet were both burning themselves into our minds as things that we could never again imagine the universe without.