Mike Brown's Planets

Five years is a long time.

Five years ago this month there was a major scientific conference in Chile on the Kuiper belt. Astronomers from all over the world converged on a small coastal town to discuss what was know and what might be learned in the future. We knew a lot about the Kuiper belt then. Or at least we felt we did. But what a difference five years have made.

Five years ago Quaoar was the largest known Kuiper belt object, and we counted Pluto as a planet. Today Quaoar is not even in the top five, and Pluto is not a planet, but just the second largest Kuiper belt object.

Five years ago the most distant object that had ever been seen was an otherwise obscure Kuiper belt object with the name 1999DG8. It is 61 times further from the sun than the earth is, in what seemed like the outer fringe of the solar system at the time. Today we know that Eris is much further away (90 times further than the earth), though it is soon going to work its way in close. But we also know about Sedna, which we would have never predicted. Sedna is currently just a little closer to the sun than is Eris, but, soon, it will be on its way out. At its most distant, Sedna is about 1000 times the distance from the earth to the sun. Sedna takes about 12,000 years to go around the sun; the last time it was this close to the sun the earth was working its way out of the most recent of the ice ages. I often wonder what will be happening on the earth the next time Sedna comes around, in the year 14,000 AD.

Five years ago, no one sitting at the conference in Chile would have ever guessed that we would eventually find an object like 2003 EL61 -- aka Santa -- the fast spinning elongated Kuiper belt object that we now know to be the product of massive collision in the outer solar system perhaps 4.5 billion years ago. And people would never have believed that we would even be able to find many of the shards from the impact and start to be able to reconstruct the original humpty dumpty.

One thing that would not surprise anyone from five years ago is that we finally found something bigger than Pluto. Most people studying the Kuiper belt assumed it would eventually happen, and I think many were finally relieved when it happened. No one could have known, of course, just how crazy the year-long debate about planets would be, but I think most of the people at the conference five years ago were pretty convinced that eventually we would fix the classification of objects in the outer solar system by placing Pluto in its rightful place with the rest of the Kuiper belt.

It was a fascinating conference five years ago, I am told. But I didn't have the chance to go. I was, by chance, also in Chile during the conference itself, but I was not sitting in an auditorium in the north of the country with my fellow astronomers, I was hiking in the southern Patagonia regions with my wife. My then-brand new wife. We were on our honeymoon. We got married on March 1st, 2003. Five years ago today. Five good years.


[disclaimer: it is still significantly proposal season, so this column only counts as procrastination when I should be working on a proposal instead.]