Pretty sunsets generally require clouds. Clouds generally ruin astronomy. But tonight I don’t mind. After 11 years of (robotically) scanning the skies almost every single night looking for planets – or at least dwarf planets – I am done, as of last night. No more fretting when a cloud appears at night. No more getting up every morning to look outside to see if it might have been clear the previous night. No more looking at the weather forecast and only wondering how it will help or hinder the search for planets. From now on, I get to mainly be a nighttime civilian.
It’s been a good 11 years. In fact, I think it is not too much of an exaggeration to say that these 11 years of scanning the skies have made a bit of astronomical history. So forgive me if I do a little reminiscing here.
The sky-scanning has evolved greatly over the past 11 years.
The very first version, started in July 1998, consisted of real people at the telescope taking real photographic plates (!) of the sky. Night after night, after our nightly pre-sunset strategizing discussions, Jean Mueller and Kevin Rykoski at Palomar Observatory would crawl out into the dark dome, load up photographic plates in the complete dark, expose them to the sky, develop them, check them, and do it all over again. When the photographic plates were finished we sent them to David Monet at the U.S. Naval Observatory in Flagstaff who digitized the photographic plates using an outrageously precise mega-scanner he had painstakingly develop just for these purposes. Finally I would get boxes and boxes of computer tapes, load them into my computer, and start searching. After three years of hard work, we had found, precisely, nothing. It was a lot of work to find nothing, too. And it was more fun than you could possibly imagine.
Soon after the initial survey ended, the telescope got a giant digital camera and a robotic brain. This refurbishment was the beginning of the golden period, when we had the privilege and fun of being the first people to ever do a modern digital camera survey of most of the sky looking for things in the outer part of the solar system. Chad Trujillo, a recent Ph.D. from the University of Hawaii, came on board to lead this new effort. Within a year we had a first major discovery: Quaoar. At about half the size of Pluto, Quaoar was the first of the huge Kuiper belt objects. It helped keep the Pluto-planet debate going strong in late 2002. I was quoted in my hometown paper as saying that Quaoar was a “huge icy nail in the coffin of Pluto as a planet.”
The robotic telescope soon got a second generation camera (which, in the end, turned out to be worse than the first generation camera; such is the way of progress), Chad moved on to a new job in Hawaii (though he stayed an important collaborator in the ongoing search), and David Rabinowitz from Yale University (who had helped build the new camera) began working with us. From 2003 until 2005 we came closer and closer to the jackpot. First we found Sedna, about 2/3 the size of Pluto, well beyond the edge of the Kuiper belt, whose orbit is still unexplained. Next was Orcus, half the size of Pluto, whose orbit is a near-mirror-image to that of Pluto. Then, in one four month period, we found the big three: Haumea (3/4 the size of Pluto), Makemake (2/3 the size of Pluto), and Eris (5% bigger than Pluto!).
That was the end of that major survey. We had finally covered as much sky as Clyde Tombaugh had 70 years earlier in the survey that led to the discovery of Pluto. But we weren’t finished.
Since 2006 we have retooled again and started searching for more things out in the distant region where we found Sedna. To do it, we basically had to cover the sky all over again. So we did. Most of this survey was carried out by a new graduate student of mine, Meg Schwamb.
And then, last night, it finished. The telescope is being fitted with a third generation digital camera which will, it is hoped, actually be better than the 1st and 2nd generation cameras. But that will be for someone else to find out. We have done pretty much everything that there is to be done from this telescope, so we decided to bow out of this new generation.
People often ask me: “Do you have any new dwarf planets that you’re tracking that you’re going to announce soon?” “Anything big coming up?” “What aren’t you telling?”
I always try to give a slightly cagey response. I never want to give away what might be coming soon.
But, now, finally, I can give you the final answer: No. That’s it. No more coming up. We have nothing up our sleeves (well, OK, we haven’t completed the analysis of last night’s data, so there is a miniscule chance that we happened to make a huge discover on the last night of our 11 year program, but that doesn’t seem so likely).
Does that mean there is nothing more to be found? Not necessarily. We estimate that we were only ~70% efficient at finding things, so there are certain to be 1 or 2 big bright dwarf planets left to be found in the places we already looked. The most likely people to find them are a group running a new survey out of the University of Hawaii. Someday I expect that I will open my newspaper and read that they discovered something bigger than Eris, or more distant than Sedna, or something else that I’ve never thought of. They’re in for a fun ride. I’ll be the one cheering them on in the stands.
I am going to enjoy my new nighttime civilian status. I am going to revel in those beautifully cloudy sunsets that used to make me feel so nervous. Well, I will enjoy it for at least for a few months. Starting next January my new student Michele Bannister is going to start a new project; she will be looking for new planets every night. But this time I won’t have the luxury of looking up at the sky to check the status. She’ll be doing it from Australia. The southern sky is the last pristine territory to search for dwarf planets. So, starting in 2009, if you see me on the street and start to casually chat about the weather, you might find that I haven’t noticed that, for example, it is raining on top of my head right now. I might instead tell you about how wonderful and clear the outlook is for the next week in southeastern Australia.