A thoroughly sporadic column from astronomer Mike Brown on space and science, planets and dwarf planets, the sun, the moon, the stars, and the joys and frustrations of search, discovery, and life. With a family in tow. Or towing. Or perhaps in mutual orbit.

Lilah Brown's Planets

Since late summer, my three year old daughter Lilah has been mesmerized by Jupiter. Every night for a few months now it has been high in the evening sky, one of the first things to pop out of the murky twilight and reveal itself night after night after night. Back in the summer we would have to go outside right at her bedtime, when it was just barely dark enough to make out Jupiter, so she could say good night. These days it is plenty dark as we drive home every day, and , for her, the highlight of the drive is the moment after we’ve climbed the little hill to our neighborhood and we take the final left hand turn to point west, and Jupiter suddenly appears in her window, high enough in the sky to even be seen from the moderate depths of her child car seat.
Anyone who, like Lilah, has been following Jupiter has noticed that it is no longer the king of the evening skies. A while back Venus crept up into the twilight to start to steal the show from Jupiter. Or, at least, in Lilah’s view, to share the show. She went from having only one planet to now having two planets to say goodnight to every night.
Lilah sees planets everywhere. You never quite realize – until you have an obsessed 3 year old – how prevalent images of planets are in everyday life. She’s got them on her lunchbox (a gift from friends who thought it would be funny if Lilah carried a lunchbox where Pluto is a planet); she sees pictures in magazines and catalogs; she sees mobiles and puzzles at stores. I would tend to just walk by them without noticing, but she always runs up – “Daddy daddy daddy daddy LOOK!” She always quickly picks out Jupiter (the big one) and, of course, Saturn. She recognizes the globe-like look of Earth. And she gets Venus right more often than I think she should.
A few nights ago, after a long cloudy spell when we couldn’t see the planets at night, Lilah looked up at the sky and was a bit startled. “Daddy daddy daddy daddy daddy daddy daddy LOOK! Jupiter MOVED!’ And she was right. While Venus and Jupiter had been slowly edging closer to each other over the past few weeks, you wouldn’t notice it unless you were watching closely. But now they were suddenly so close that even a three year old could look and see that something had changed.
As much as I am charmed by Lilah picking out pictures of planets in magazines to show me, having her point out to me that Jupiter moved was – for me – the pinnacle of planetary charm. While most kids and adults can name the planets and point out pictures, almost nobody notices the real thing even when it is blazing in the evening sky. Planets are not just things that spacecraft visit and beam back pictures from. They’re not just abstractions to put on lunch boxes. They are really there night after night after night, doing what only planets do: moving.
Last night – Saturday – the show got even better. The sliver moon showed up low in the early evening sky anda began working its way toward Jupiter and Venus. For half of the month, Lilah and I watch the moon get bigger and move east night after night in the evening sky, so we both know what is going to happen next. Based on how far the moon is from Venus and Jupiter, it looks like on Monday night the moon will be packed tightly in the evening sky with Jupiter and Venus. It will, I suspect, be a spectacular sight, with the three brightest objects ever visible in the night sky in an unmistakable grouping in the southwest just after sunset. It’s the sort of site that I think – that I hope – will make even non-night sky watchers suddenly look up and wonder. And when they look the next night, to see if it is still there, they will notice the moon has already moved further east and gotten a little bigger, and they will see that two other bright lights – Jupiter and Venus – are in slightly different spots. Maybe even a person or two will follow the moon’s movement for the next week as it grows to full. Maybe a lucky few will watch as Jupiter gets lower night after night, leaving Venus alone in the sky by next month. It’s a show worth following. I know Lilah and I will.
I’m on a flight across the country tonight. I touch down long after Jupiter and Venus and the Moon will all have set in Florida. As I was packing my bags this morning Lilah asked: “Daddy, are you going away to go talk about planets?” Yes, Lilah. I’m going away to talk about planets. I forgot to tell her, though, that I’m going to see some, too. I was sure to pick a window seat on the south side of the airplane so I could watch the show from the air. And when I arrive I’ll call back home and tell Lilah all about it and tell her to go outside right now and LOOK! she can see all of our favorite planets and LOOK! the moon has moved and grown and I’m sorry that planets are taking me far from home tonight but I’m glad we have these here in the sky to share tonight and forever.

A winding path

I’m in Tucson this week and right now about to go out to dinner as part of three days of talks and meetings and lunches all in conjunction with me being awarded the Marc Aaronson Memorial Lectureship this year. I do not tend to talk much about things like this because it seems a bit unseemly, but I am going to break my usual silence and tell you why this particular award is particularly meaningful to me.
The award is given every 18 months to an astronomer who makes a significant contribution to observational astronomy at a young age. I’m happy they didn’t check the birth date on my driver’s license. The lecture itself was last night, at the University of Arizona, and I began my lecture with a story I have never told anyone before. I said something like this:
There are several reasons why I am quite flattered and honored to be receiving this award. First, the list of the people who have received the award over the past two years is particularly impressive. It is thoroughly flattering to be considered to be in the same company as people who I think of as superstars in the field. It’s also gratifying to receive such an award from what I still can’t help but think of as “real astronomers.” Astronomers who study the solar system have long been considered the ugly step-sisters of astronomy. Nobody really wants to give us telescope time or accolades or awards. In fact, we had to set up our own societies so we could give each other awards and not feel totally left out.
Both of those reasons for being honored to receive the award, however, would be reasons I could give no matter what the award was. But, to me, receiving the Aaronson award means even more.
When I was a senior in college in 1987 [which, by the way, means I just had a 20th college reunion, which I am pretty sure disqualified me from being considered “young”] I found what I thought was going to be the field in which I was going to make my career. I had been doing research projects with physicists who were interested in the large-scale structure of the universe – where galaxies are, why they have the distributions they do – and I thought that that was about the most interesting thing that any human could possibly study. The only problem with the projects on which I was working was that there were more theoretical or computational than observational. I wanted to be someone who went out to telescope and collected data and discovered things myself. I didn’t want to just sit in the computer lab in the basement and make endless computer models about how the universe might be, I wanted to go out look at the night sky and figure out how it actually is.
Nobody did that at my university, so I started looking around to see if anyone did that anywhere. Every time I looked up the topic or anything related, a single name would always pop to the top: Marc Aaronson. Aaronson was an astronomer at the Steward Observatory at the University of Arizona, and he was doing exactly what I wanted to be doing. I decided that what I really wanted was to be Marc Aaronson, but that, since this seemed unlikely, I was going to go to graduate school at the University of Arizona and I was going to work with Marc Aaronson.
That spring, Aaronson was crushed to death by the dome of telescope where he was working.
I decided maybe I wouldn’t go to graduate school. I went biking around Europe instead.
The following year I was ready to go, but Arizona didn’t seem right anymore. I ended up at U.C. Berkeley working with someone who did generally similar research on distant galaxies. Which, through a path that is convoluted to explain but extremely clear in my head, led to my Ph.D. thesis on the magnetosphere of Jupiter and my current work on the outer solar system. Which led me to Tucson, to receive the award. The citation reads:
Marc Aaronson Memorial Lectureship
Awarded to
Dr. Michael E. Brown
California Institute of Technology
November 21, 2008
for his outstanding research and lasting contribution to astronomy through the characterization of the outer solar system and the discovery of objects comparable to Pluto
To which, they could have added, which all came about through a winding complicated path whose direction was never certain, but whose start was clear after being pointed out by Aaronson.
I never met Marc Aaronson, but, based on his wife and daughter, who I met yesterday, I think I would have liked him. If I’d had a chance, I’d like to have said “thanks.”

Land ho!

If you pay any attention to space news, or even just to the front page of the LA Times you will know that this week brought reports of the first-ever pictures of planets beyond our solar system.
I had no inside scoop on this one, so I learned it the hard way: a reporter called me up to ask for commentary. My immediate comment: “uhhhh…. Can I go and read the scientific paper first?” A good reporter will say “of course” but many less good ones will say “well I just want a quick quote; can you give me a reaction?” Luckily, this one said “of course.” I read the paper. Papers, actually. Two groups of astronomers had taken pictures of planets around other stars at about the same time. I went into reading-a-scientific-paper mode and started asking the standard questions that I ask whenever a read a scientific paper:
· Do I believe the results? I tend to be quite skeptical of results, whether they are mine or anyone else’s. Cutting edge science is hard, or someone would have done it already. There are many ways to make mistakes and to misinterpret data, particularly when you desperately want a certain result to occur. These astronomers clearly want their results to tell them there are planets. Did they take any shortcuts that could have led them astray? Did they stray into wishful thinking? I read carefully looking for sloppiness, as I would do when reading any other scientific paper.
In this case there appeared to be no sloppiness, and no wishful thinking. The observations were quite meticulous. The analysis solid. I don’t see any reason not to believe that they had indeed seen something. So far so good.
· Do I believe the interpretation? At this point, I believed that, yes, indeed, the thing that had caught their attention in their data was probably real. I d something. But what was it? Was it really a planet, like they claimed? Many scientific papers can be meticulous about discovery and then sloppy about interpretation. The reason for the sloppiness is often, again, wishful thinking. The astronomers here saw something, and they really wanted that something to be a planet. That desire for discovery can lead to data cherry picking just like that that has often been discussed about the intelligence community interpretation that there were weapons of mass destruction in Iraq. You pay close attention to the data that supports what you want to be true, you discount data which is less supportive. Scientists are supposed to be driven purely by facts and immune to such thinking, right? Well, no. Science is supposed to be driven by facts, but scientists are just people who can’t help but be influenced by many outside things.
Did it happen here? I kept reading. I couldn’t find any flaws in their interpretation. They did all of the things that they needed to do to really prove that what they were seeing was a planet going around a distant star. They didn’t ignore any of the counter evidence. The news was good. I believed the results and the interpretation. Only one question more to go!
· Do I buy the spin? Any paper that is being covered by the press is being spun, whether the authors intend for it to be or not. Sometimes the spin is fair, sometimes it is a bit oversold, and sometimes the spin can be so off that it takes an accurate scientific paper and turns the public interpretation into bad science. These papers about imaging planets around other stars were, in my opinion, a bit oversold. These pictures of planets around stars were more of a long-expected technical milestone than astounding discovery.
OK! I was ready to talk to the reporter. What to say? I thought through my reactions: yes, these really were the first images of planets outside of the solar system; yes, the scientists are good and credible; yes, people have been working for a long time to achieve this thing. But how was I going to deal with the other thoughts that I had? No, this was not nearly as exciting as people were making it out to be. We have known about planets around other stars for more than a decade now, and taking a few pictures adds very little to our scientific understanding of them. There was a race to see who could take these pictures first, not because anyone really had many questions about what the planets would look like, but simply so that someone could be declared the winner and put the feather in his cap.
That’s not a very kind thing to say about work by a colleague who has worked hard to achieve this result. And it’s not really what a reporter – searching for the breathless quote – wants to hear. Yet that was my initial reaction.

o o o o o o o
Five years ago today I discovered Sedna. Sedna is an unexpected oddity in the outer solar system. It is on a looping 12,000 year long (!) orbit around the sun that carries it as far away as 1000 times the distance from the earth to the sun and as close as 76 times the earth-sun distance. Nothing else known has such an orbit, and no one really knows how Sedna got there. For five years we’ve been searching hard for something else like Sedna, and, so far, we’ve come up blank.
Four and a half years ago, we had a big press conference to announce the discovery. As usual, the reports called up other astronomers around the world for comment. Some were indeed quite excited by the discovery, but more than a few told the reporter some version of “well, it’s true, but it’s really no big deal. We’ve know to expect things like this for a long time so it is not surprising that someone found one.”
Most scientists don’t talk to the press that much, and, when they do, they talk to them like they would talk to another scientist. When talking to a fellow astronomer, for example, I am able to step back and freely say that the discovery of Eris was not particularly a big deal. It was simply an object slightly larger than Pluto with very few intrinsic scientific implications (Sedna, in contrast is a big deal and has huge implications, but that discussion will have to wait). It became a big deal culturally, as it precipitated the long-discussed downfall of Pluto, but, scientifically, it really didn’t change much of the way that we view the solar system.
When reacting to scientific papers, scientists are more used to the idea of peer review (more on this next week!), where you are supposed to be detached and point out the good and the bad and the utterly mistaken parts of a paper. You are certainly not supposed to be excited.
But commenting to the public on scientific papers is not peer review. Reporters are not scientists. They are not reporting to scientists. They are reporting to people who have a million other bits of news coming in and may or may not pay attention to this one. But if they do pay attention to this one, they will actually think about and learn a little bit about science that day. Any scientist should be happy when that happens. The role of the commenting scientist in this case is not to downplay the significance of some other scientist’s result, but to explain the excitement.
After the experience with Sedna (and, later, Eris and Haumea and Makemake, which all went through the same process) I thought hard about the right way to interact with scientific news. These days, I try to keep in mind my:
Five Rules for a Scientist Talking to the Press about Someone Else’s Result
1. Momentarily forget scientific detachment: If the result is exciting, allow yourself to be excited. Explain why you’re excited.
2. Re-explain the science. More often than not, the person talking to you has heard more of the spin than the science. The science is actually the cool part. Emphasize it.
3. Resist the cliché. In commentary about exo-planets, someone will invariably say “and this will help us discovery earth-like planets.” For Mars the cliché is “and we can look here for life.” For Titan: “and no we will better understand the origin of life.” Clichés are nice things to say, since you don’t have to think much to say them, but, as a consequence, they don’t actually mean much, either. And, since they are clichés which can be used for almost anything, they don’t do much to actually explain the science. The real science is probably much more interesting than the cliché.
4. Never ever hesitate to point out bad science. Bad science is worse than no science. Never hold your nose and pretend to be excited when things smell funny. In many circumstances, explaining why something is bad science provides an excellent education as to what good science should be. If the science is good but the spin makes it bad, unspin. Talk about what the science really says.
5. Congratulate and thank your colleagues. Someone did something good that allowed you to have a chance to do a little public scientific education. Send him or her a quick email and say thanks and job well done.
The reporter called back to talk about planets. I was excited. I re-explained the science and why it mattered. I talked about how interesting it is to me to start to see the architecture of other planetary systems and what this will tell us about planets near and far. At the end of the interview I summed up my thoughts in a way that, in retrospect, I like enough to repeat here:
I can’t say the pictures are surprising. We have known for a long time that these planets are out there and that someone someday would take pictures of them. But that doesn’t take away from the exciting fact that we are seeing planets around other stars for the first time. When you start to sail across the ocean you know that you are finally going to reach shore, but, still, when you see land for the first time it is the most beautiful and exciting thing in your universe. “Land ho!” is never said in a quiet voice.
And then I hung up the phone and sent congratulations to my colleagues for their exciting discoveries.

Moon shadows galore

Last spring I was extremely excited about the possibility that there was a possibility that the orbit of the satellite of the Kuiper belt object 2003 EL61 might be precisely edge-on when seen from the earth (you can re-read all about it here). As I explained then, such a thing only happens twice each orbit – so only once every 140 years in this case – and has the possibility to teach us an amazing number of things. When we finally got the data and precisely figured out the orbit we were excited – it is edge on – and dismayed – it was only going to be edge on for one more month. We had basically missed all of the action by 2 years and would have to wait 140 more years to see it again.
Things have changed since the spring.
First, 2003 EL61 is now, of course, Haumea, and the satellite with the edge-on orbit is the small inner one, Namaka. Haumea also has an outer satellite Hi’iaka. And Hi’iaka changes everything. When we did our preliminary calculations in the spring we did the comparative simple job of considering Namaka in isolation. It took us the remainder of the summer to get a solution to the full problem, where we also figured out how the orbit of Namaka changes due to the gravitational influence of Hi’iaka (“us” and “we” here is a euphemism for “my graduate student Darin Ragozzine” who actually did all of the work as part of his Ph.D. thesis). We knew there would be an effect, but we assumed early on that it would be a minor perturbation. It is, in a sense, a minor perturbation, but it makes all of the difference in the world.
Hi’iaka ever-so-slightly twists the orbit of Namaka, slowly changing the direction it is pointing. It doesn’t change by more than a degree or two a year – almost imperceptible! But, due to luck or fate or karma or cosmic design, it is changing it just enough to keep the orbit edge-on as seen from the earth for longer than usual. Normally the edge-on events would last for maybe two years. Because of Hi’iaka, they are going to last eight years! So, OK, we have missed the first two years, but we have six more years of this to go!
What are we going to see?
Namaka goes around Haumea once every 19 days. So every 9 ½ days Namaka either goes in front of or behind Haumea. We don’t have any telescopes that are good enough to see the actual event take place; it’s all much much too small. Instead, we’ll simply notice that at the moment Namaka goes behind Haumea and disappears, the whole system gets a little fainter.
Measuring a lot of these disappearances means that we will be able to reconstruct the shape of Haumea pretty precisely. Haumea is that strange object that we think is shaped like a squashed football; a precise measurement will teach us much about how and why such a crazy thing could exists.
So we need to measure a lot of these disappearances.
The problem is, they happen at specific times. It’s only nighttime over half of the earth at a time. And Haumea can only be seen by half of the earth at a time. And those two halves are not precisely the same. So there are sometimes only little slivers of the earth when it is night time and also Haumea is up in the sky. And we don’t have telescopes on all of those little slivers. So what to do?
We don’t have telescopes everywhere, but other people have them in many places. We are right now attempting to encourage a huge international collaboration to all measure these events from wherever they can best be seen (you can see the web site where we explain to astronomers what is happening). We will then all pool our data together and see what comes out. These observations are a strong case for such cooperation; a small number of measurements from just one location are almost worthless, but the full set will be priceless.
We’ve started signing people up already. First, we will be observing from our own telescopes at Palomar Observatory east of San Diego. We quickly enlisted people in Hawaii and Australia. These three telescopes cover the western US and the Pacific. We then have a huge gap of India and China and Russia and Europe until we get to a telescope that we hope to be able to use in the Canary Islands. We’ve contacted and had encouraging responses from the two largest telescopes in India and from a telescope in Armenia.
We’ve got much to do. The first good event occurs on December 7th and then they occur every 9 ½ days until about June when Haumea is too close to the sun again to see. We’re in good shape for about half of them but still struggling to get more telescopes. By next year, though, perhaps we’ll know what we’re doing a little better and we’ll get it all down smooth. And then we’ll still have 5 more years of events to go!
It’s hard to predict just how much we’ll learn about Haumea in these five years, but I think it is safe to say that Haumea, which I’ve long said is the single most interesting object out there in the Kuiper belt, will only get more and more interesting with time.

The End

This evening I am going to do something I have rarely done in past 11 years. I am going to go outside and hope for a pretty sunset.

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.

What is a dwarf planet?

Now that the IAU has officially declared the fifth dwarf planet (in order of size: Eris, Pluto, Makemake, Haumea, Ceres), we are likely in for a dry spell on new dwarf planets. The preliminary searches of the sky are all but complete, and (as far as I know) no one has any new objects the size of Haumea hiding in their back pockets. We'll probably be at five official dwarf planets for a while.

Now is a good time, then, to remind ourselves what a dwarf planet really is.

When the final vote on the definition of "planet" was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined. The "dwarf planets" are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. The best description I can come up with is that a dwarf planet is something that looks like a planet, but is not a planet. The official definition is that dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction.

Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object which is geologically dead and one which might have interesting processes worthy of study.

[Haumea is, of course, not round, but that is only because it is spinning so fast. If you stopped it spinning it would become a sphere. That still counts.]

So how many dwarf planets are there? Five, of course. The IAU says so.

But let's ask the more scientifically interesting question: how many (non-planet) objects in the solar system are large enough to be round due to their own gravitational pull?

Still five, right?

Well, no. Here is where the IAU and reality part ways.

There are many more objects that precisely fit the definition of dwarf planet but that the IAU chosen not to recognize. But if the category of dwarf planet is important, then it is the reality that is important, not the official list. So let's examine reality.

So how many dwarf planets are there? Ceres is still the only asteroid that is known to be round. After that it gets complicated. All of the rest of the new dwarf planets are in the distant region of the Kuiper belt, where we can't actually see them well enough to know for sure if they are round or not.

While we can't see most of the objects in the Kuiper belt well enough to determine whether they are round or not, we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round.

The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn's satellite Mimas, which has a diameter of about 400 km. Several satellites which have diameters around 200 km are not round. So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round, and thus a dwarf planet. We might be a bit off in one direction or another, but 400 km seems like a good estimate.

How many objects larger than 400 km are there in the Kuiper belt? We can't answer this question precisely, because we don't know the sizes of more than a handful of Kuiper belt objects, but, again, we can make a reasonable guess. If we assume that the typical small Kuiper belt object reflects 10% of the sunlight that hits its surface we know how bright a 400 km object would be in the Kuiper belt. As of now, about 50 objects this size or larger are known in the Kuiper belt (including, of course, Eris, Pluto, Makemake, and Haumea). Our best estimate is that a complete survey of the Kuiper belt would double this number, so there are roughly 100 dwarf planets in the Kuiper belt, of which 50 are currently known.

The new dwarf planets in the solar system are very different from the previous 8 planets. Most are so small that they are smaller across than the distance from Los Angeles to San Francisco. They are so small that about 30,000 of them could fit inside the earth.

Does it matter how many dwarf planets we say there are?

I think the answer is "yes." If you believe that there are only 4 dwarf planets in the Kuiper belt then you place an oversized importance on those 4 objects and you get an exceedingly warped picture of what the outer solar is like. The important thing about the Kuiper belt is that beyond Neptune there are many many many objects with hundreds being large enough to be round. The four "IAU Dwarf Planets" in the outer solar system are all fascinating objects -- hey! I discovered 3 of them, I must think there are at least a little interest -- but it would be a gross exaggeration to think of them as the only objects, or even the only important objects, in the fascinating region of space beyond Neptune.


On December 28th, 2004, I discovered a Kuiper belt object brighter than anything anyone had ever seen before. Being only a few days after Christmas, I naturally nicknamed it Santa.
The discovery was bittersweet. I had made a bet with a friend 5 years earlier that someone – anyone! – would discover a new planet by January 1st, 2005. The deadline was in 3 days, but I knew that Santa didn’t count. We didn’t know exactly how to define “planet” back then, but we decided that something of a particular brightness would count. Santa was bright , but not quite bright enough. Three days later I had still not found anything bright enough to count, and I lost the bet.
But, still: Santa! How would I have known back in 2004 that Santa would be the single most interesting object ever discovered in the Kuiper belt? It has a moon – wait, no, two moons! It is oblong, sort of like a football (American style) that has been deflated and stepped on. And it rotates end over end every 4 hours, significantly faster than anything else large known anywhere in the solar system.
Large? Well, at least sort of large. The long axis is about the same size as Pluto or Eris or Makemake. Back when I thought that maybe the IAU was going to vote that anything the size of Pluto or larger was a planet I was going to argue that Santa was indeed a planet – as long as you looked at it at exactly the right angle (luckily, the IAU was much more sensible, so I did not have to make such a crazy argument).
Stranger still, Santa has the density of a rock. We think that most things out in the Kuiper belt are about equal portions of rock and of ice, but, apparently, this does not apply to not Santa. It’s only rock. Except that even that is not true. When we finally got a chance to look closely at its surface with the Keck telescope we realized that the surface is nothing but ice. Santa must have a structure like an M&M, except that instead of a thin layer of sugar surrounding chocolate, the thin outer shell is ice and the interior is rock. Don’t bite.
These characteristics already make Santa the strangest object in the Kuiper belt. Several years ago we came up with what thought was a good explanation. What if, eons ago, Santa was an even larger Kuiper belt object and it got smacked – in a glancing blow – by another Kuiper belt object? That would explain the fast spin. And the fast spin would be enough to explain the oblong shape; anything spinning that fast would be pulled into such a big stretch.
What’s more, the initially large Santa could have had a rocky interior and icy exterior, much like the Earth has an iron interior and a rocky interior. When the huge impact occurred, it could have cracked that outer icy mantle and ejected all of that ice into space. The two moons that circle Santa are pieces of that icy mantle.
This explanation was, we thought, pretty good. And then it got really good.
While looking across the Kuiper belt at many different objects, we realized that a small number of objects in the Kuiper belt look like tiny little chunks of ice. How strange. Even stranger, though, was that all of these chunks of ice were, relatively speaking, next-door neighbors of Santa. We had found the other chunks that had been removed from the mantle of Santa. The story was complete.
After we discovered Santa, we worked hard to get the first scientific paper ready to announce the discovery. In science there is always a tension between doing the careful work to make a complete announcement and doing an instant but incomplete announcement in order to make sure you don’t get scooped. We were as worried as anyone about being scooped, but we resisted the temptation for instant announcement. We felt that the science was too important.
On July 7th 2005, as I was putting the finishing touches on the scientific paper, in hopes of submitting it the next day, I had a minor delay. My daughter was born. I had somehow convinced myself that there was no way that she would be born for another week. I was certain that I had more time. But I had no more time, no more time at all. I forgot about Santa and the rest of the Kuiper belt and turned my obsession from it to her. The announcement about Santa would have to wait, I was too busy sending out announcements about Lilah, instead. What difference would a few months make, really?
The announcement did indeed wait, but only for 21 more days. On a late Thursday night, between changing diapers and filling bottles and descending ever more into sleep deprivation, I checked my email and saw the announcement of the discover of Santa myself. A previously unheard-of Spanish team had just discovered Santa a few days earlier. And they called it the tenth planet.
No no no no no no no no! I was horrified. My discovery had just been scooped by a group who decided not to wait to learn more. They didn’t know any of the information about Santa that we did, in particular that it has a satellite and from the orbit of the satellite you could tell that it was only 1/3 the size of Pluto, and that it was definitely not the tenth planet. Worse, a few months earlier, we had actually discovered something that was bigger than Pluto. This was going to cause nothing but confusion.
That night, on no sleep but much caffeine, I stayed up to finish the paper about Santa that I had put aside three weeks earlier. We would not get credit for discovery, which was painful enough, but at least we would quickly set the record straight about its size and importance. After I sent the paper off, I sent a quick email to congratulate the Spanish team on their discovery and I filled them in on everything that we knew so that they could answer questions from the press correctly. Finally I nodded off to sleep.
I woke to a nightmare. In the intervening hours it appeared that someone had used the knowledge that we had been tracking Santa to start looking into what else we had been doing. Someone had traced where we had been pointing our telescopes for the past months. We had been pointing them at the object that would one day be called Eris – the object bigger than Pluto, the real tenth planet! That morning, the astronomical coordinates of Eris were posted to a public web page with discussions about what might be there that we had been watching. It was clear to me that as soon as the sun went down that night, anyone with a moderately large amateur telescope could point up in the sky at those coordinates and, the next day, claim they had discovered the 10th planet.
After breakfast, I apologized to my wife; I would have to go in to work today for the first time in three weeks.
I called my wife later in the day to apologize again. I was going to have an international press conference that afternoon and would she mind bringing me some nicer clothes? And a razor, perhaps? And more coffee. Definitely more coffee. That evening, the world learned that there were 10 planets.
After more than three years, Santa received a formal name today. Santa is now, and forever, officially Haumea. From the official citation issued by the International Astronomical Union:
Haumea is the goddess of childbirth and fertility in Hawaiian mythology. Her many children sprang from different parts of her body. She takes many different forms and has experienced many different rebirths. As the goddess of the earth, she represents the element of stone.
The name was chosen by David Rabinowitz of Yale University, one of the co-discoverers of Santa (along with me and Chad Trujillo of Gemini Observatory in Hawaii). He chose the name because Haumea is closely associated with stone, and Santa (as we knew it at the time) appeared to be made of nothing but rock.
But the name is even better than that. Just like the Kuiper belt object Haumea is the central object in a cloud of Kuiper belt objects that are the pieces of it, the goddess Haumea is the mother of many other deities in Hawaiian mythology who are pieces pulled off of her body.
Two of these pieces are Hi’iaka, the patron goddess of the big island of Hawaii, who was born from the mouth of Haumea, and Namaka, a water spirit, who was born from the body of Haumea. These names were chosen for the brighter outer moon and the fainter inner moon, respectively.
Haumea I, Hi'iaka, discovered 2005 Jan 26 by M.E. Brown, A.H. Bouchez, and the Keck Observatory Adaptive Optics team

Hi'iaka was born from the mouth of Haumea and carried by her sister Pele in egg form from their distant home to Hawaii. She danced the first Hula on the shores of Puna and is the patron goddess of the island of Hawaii and of hula dancers.

Haumea II, Namaka, discovered 2005 Nov 7 by M.E. Brown, A.H. Bouchez, and the Keck Observatory Adaptive Optics teams

Namaka is a water spirit in Hawaiian mythology. She was born from the body of Haumea and is the sister of Pele. When Pele sends her burning lava into the sea, Namaka cools the lava to become new land.
But wait! Shouldn’t the official discoverer get to name the object? What of the Spanish team?
Yes. The discoverer should.
Several weeks after the Spanish team announced the discovery of Santa which precipitated the announcement of the object that would eventually be named Eris, which precipitated the entire discussion of dwarf planets, it became clear that the Spanish team had not been forthcoming. They themselves had been the first to access the web sites which told where our telescopes looked. And they did this access two days before they claimed discover (you can see a detailed timeline reconstructed from the web logs here)
Did they use this information to claim the discovery for themselves?
As a scientist, my job is to examine the evidence and come up with the most plausible story. Here are some possibilities. It is impossible to disprove this story, claimed by the Spanish team: while looking through two-year-old data, they discovered Santa legitimately, and then, only hours later, accessed information about where our telescopes had been looking and were shocked (shocked!) to realize that the object they had just found was the same object that we had been tracking for months. Wanting to establish priority, they quickly announced, knowing essentially nothing about the object.
Though this story cannot be disproved, it does not have much of an air of plausibility about it. Data that were two years old happened to get analyzed just hours before – whoops! – the team found out that someone else had found the same thing? Hmmmmm. Perhaps most damning, you would think that perhaps the Spanish team would be willing to admit this early on. Instead they appeared to attempt to hide the fact that they ever knew anything about our telescope pointings.
Let’s try a more plausible explanation: the Spanish team found our telescope pointings, used that information to infer the existence of Santa, and assumed that no one would ever know they had not found it legitimately.
No way to prove it, but the later hypothesis certainly sounds more plausible. To be fair, though, I don’t think there is any way to ever know the full extent of the truth, except on the off chance that someone on the Spanish team eventually spills the beans about what really happened. I keep waiting, but I don’t hold my breath.
But wait, there’s more to ask! If the telescope pointings were – even if inadvertently – on a publicly accessible web site, was it wrong to look at them? The obvious answer is that there is nothing wrong with looking at information on any publicly accessible web site, just as there is nothing wrong with looking at books in a library. But the standards of scientific ethics are also clear: any information used from another source must be acknowledged and cited. One is not allowed to go to a library, find out about a discovery in a book, and then claim that discovery as your own with no mention of having read it in a book. One is not even allowed to first make a discovery and then go to the library and realize that someone else independently made the same discovery and then not acknowledge what you learned in the library. Such actions would be considered scientifically dishonesty.
In the end, while we are likely to never know exactly what happened, it appears clear that the Spanish team was either dishonest or fraudulent. They have claimed the facts that merely make them dishonest. If I had to bet, though, I would bet for the later.
Officially, the naming of Haumea does nothing to put to rest this three-year-old controversy. The committee that voted to accept the name has said that, while they will take the name proposed by our team rather than the name proposed by the Spanish team, they are not favoring one claim over the other. They will let posterity decide.
OK, posterity, have at it. If I am no longer around to hear the news on the decision, that’s ok, you can tell my daughter Lilah instead. She will have been waiting, nearly precisely, her entire life.

The Joys of Rejection and Lake-effect clouds on Titan

Remember my new paper that describes my interesting discoveries about Titan (see Your Saturday Newspaper)? submitted it to Science magazine a few weeks ago in the hopes that it will be published and some day make it to your Saturday newspaper. But it won't. It has been rejected.
It was a kind rejection. They didn't say "we think you're paper is wrong." Just, "we don't find it of general enough interest to publish in our journal."
Rejection is always hard. My first response was generic sputtering “wha.. wha… what?” and then disbelief “this can’t be!” and anger and dismissal “those idiots don’t even know what they are missing.” This sequence lasted about 7 seconds, and then I got over it. After about 1 minute I became excited.
Why be excited about rejection from Science? Along with the publicity benefits of publishing a paper in somewhere like Science comes the hard part. You agree not to publicize or discuss the paper before the publish it. This process can take 6 months or longer.
But having been rejected from Science, I quickly turned around and submitted the paper to a more specialized journal -- Geophysical Research Letters (aka GRL) -- which has no such restrictions, and then I went a step further and submitted it to an on-line electronic archive ( which means you can go read it right now! http://lanl.arxiv.org/abs/0809.1841 ).
Scientists these days are increasingly speeding up the slow process of formal publication with an informal process of web publication. Such web publication has good and bad aspects to it. Good: instant. Bad: unreviewed.
Anything that is published in a major journal has had one or two experts read it closely and suggest changes. My paper on Titan is currently undergoing this process at GRL, and, when the reviewers are done, I will modify and respond. But my paper is on the electronic archive for everyone to see before that even happens.
Posting a paper on-line before it has been reviewed can lead to great embarrassment. What if the paper has fundamental flaws and needs to be withdrawn or rejected? What if the referees point out places where major changes need to take part? All of this is certainly possible, and should make any on-line submitted wary. But, for me, the benefits outweigh the risks. I am sufficiently confident in the accuracy of what I did that I am not worried about any of these major problems. While there is no doubt that the reviewers will suggest some improvements, I don’t believe the overall conclusions of the paper will change significantly. And I think the conclusions are sufficiently interesting that I relish the idea that people will begin to read the paper and think about the results now, rather than 6 months from now. So I submitted.
And now, even better, I can talk about the discovery of lake-effect clouds on Titan.
Earlier this summer, while looking through NASA’s on-line archives of images of Saturn’s satellite Titan taken from the Cassini mission, I began to notice a recurring pattern up near the north pole of the satellite. The north pole of Titan has been in the darkness throughout a long long winter (a full year on Titan takes 30 years; winter is almost a decade) and is just now emerging into some spring time daylight. As it began to emerge, I noticed what appeared to be tiny little clouds popping up and disappearing right over the pole.
Titan is in some ways bizarre and exotic yet in some ways very earth-like. Both earth and Titan have mostly-nitrogen atmospheres; on both the surface pressure is about the same (the big difference on Titan: it lacks that minor contaminant – oxygen – that makes the earth a more interesting place….).
Titan and earth are the only bodies in the solar system known to have large expanses of liquid at the surface. On Titan, though, the temperature is so low that water is frozen solid. The lakes of Titan are made, instead, of methane and ethane. If you could figure out a way to get a pipeline there, Titan’s lakes could supply all of our needed natural gas for years to come.
On earth the liquid water is globally distributed. On Titan it appears that the liquid methane and ethane is confined to the poles.
Finally, Titan and earth both have clouds in its atmosphere, and these clouds are made from the dominant liquid on the surface. On earth: water. On Titan: methane.
Now, back to the little clouds I had seen popping up at the north pole during Titan’s early spring.
These clouds surprised me; they appear to be cumulous clouds – like large thunder heads. On the earth we only get such clouds in hot, humid places. Arizona in August. Year-round in the tropics. Temperate latitudes during summer storms. How could such clouds possibly be up at the north pole just as winter is waning?
It occurred to me that we do get winter cumulus-type clouds on the earth in at least one case: lake-effect clouds and storms. Lake-effect storms on the earth are those winter storms that blow across the Great Lakes, pick up moisture, and then proceed to dump many many feet of snow on places like Buffalo, New York.
The effect occurs in many other places around the world. Or, I should say, they same effect occurs in many other places around the solar system. I believe this process is precisely what is causing the sporadic clouds at the north pole of Titan.
Like everything else, Titan and earth have similarities and differences in their lake-effect clouds, too. On the earth, the formation of these clouds is greatly aided by the fact that deep lakes stay relative warm over the winter. So as cold air passes over these lakes the air both picks up humidity and a little heat. This heat causes the air to rise (like a hot air balloon) which, in turn, causes those cumuli and the subsequent snow.
On Titan, a decade of polar winter means that none of the lakes retain any heat, so passing air only picks up humidity (methane humidity, in this case). Something else needs to help push the air higher to cause those cumuli. In the paper, we speculate that there might be mountains at the north pole that help, but really that is just a wild guess.
Cold lakes won’t evaporate, so these clouds have only started to become active in the last few years as sunlight has started to every-so-slightly heat the lakes. Every time the lakes warm up just a bit, a huge dollop of evaporation occurs, which re-cools the lake, and we see a cumulus cloud pop up. The lake then has to wait for some more sunlight before it happens again.
If our general story is correct – and I think it is – then as spring and then summer approaches at the north pole, the sunlight will increase dramatically, and the lake-effect clouds will start to go crazy. And we’ll be watching. The Cassini spacecraft is slated to continue flying past and taking pictures of Titan for several more years. And we might find more exciting things.
And what will we do when we find exciting things? Well, in the end I will probably never learn my lesson. We’ll submit them to Science. Or we’ll submit them to Nature. And then we will have to wait for months to talk about them. And maybe they will get a paragraph in your Saturday paper. But, if we – and you – are lucky, we will instead be rejected, we’ll post to a freely available on-line archive, and everyone can hear early about the latest happenings on this bizarre satellite.

The occult sciences

Last weekend I had my first experience with the occult sciences.
Maybe I should rephrase that.
Last weekend I did my first occultation science. That’s what I meant.
Occultations are interesting events that can be seen here on earth. They are like miniature total eclipses except that instead of the sun being blocked, it is a star. And instead of the moon doing the blocking it is something else, an asteroid, a planet, a Kuiper belt ice ball. You know an occultation is occurring when a star suddenly disappears and then reappears seconds to minutes later. Something dark must have moved in front of the star.
Scientifically, occultations provide a unique glimpse at the dark object that is passing in front of the star. If you measure how long the star disappears and you know how fast the object was moving, you have just directly measured the size of the object. Or at least measured the size of the object across one line. To really measure the full size of the object you need more than one line. To do that, you station astronomers in something resembling a north-south string over the full expected size of the object. Everyone watches and carefully times the event, and then you combine all of the information to find out the real size and shape of the object. If you’re lucky, you might even detect that the star does not blink out, but fades out, instead. This fading shows the atmosphere of the object. If you’re even luckier, you might see a second disappearance of the star a little before or after the main event. You would have just discovered a moon of your object.
The occultation last week was by a large Kuiper belt object. Kuiper belt objects are so far away and appear so small from our point of view that the probability of one of them covering up a star at any point in time is quite small. Astronomers carefully track these Kuiper belt objects and carefully measure positions of stars over and over in the hopes that one of them will be found to occult.
Sometimes these predictions can be made months ahead of time and astronomers can prepare for the event. Sometimes, like for the one last week, no one knew for sure that the occultation would occur until a last set of careful measurements of the position of the star occurred a few weeks before. Suddenly it appeared that this occultation would be visible across much of North America and that the path would go over some of the major observatories: McDonald, Kitt Peak, Palomar, Lick.
With only two weeks to prepare, though, it is tough to suddenly get a telescope. All of the large telescopes are fully scheduled months in advance, but there sometimes some observatories have smaller telescopes that can be made available at shorter notice if you know the right person.
At Palomar, the right person to know if you want to observer on the brand-new 24-inch robotic telescope is me. I’ve been constructing this new telescope for an embarrassingly long time now, but it is almost finished and ready for real scientific observations. One of its major long-term projects is to monitor Saturn’s moon Titan for signs of major storm activity. But the telescope is still not quite ready yet; we hope to really have it finally commissioned by October.
But when we heard that this occultation was potentially going to be visible from Palomar we decided it was worth going up and trying to use this little telescope even though it was not quite ready.
We arrived Saturday afternoon for the Sunday occultation. Emily Schaller – my now former graduate student (who moved to Hawaii last week to begin a new position as a Postdoctoral Fellow at the Institute for Astronomy at the University of Hawaii) – and I left Pasadena at noon, stopped once for coffee, and arrived at Palomar Observatory at around 3pm. We went right to the small dome of the 24-inch telescope, unlocked the door, and peered inside a bit apprehensively. No one had even been in side for the past few months as we were waiting for the final control systems to be finished. We knew that there was a moderate chance that something would have broken over this time period and the telescope simply would not work. We knew that last winter the dome had leaked. What would we find?
To our relief, everything looked fine. We plugged the telescope and the computer that controls it in and double checked that we could, at least, move things. We could! We set to work to get things going. We had brought some new software up on a laptop to control some important auxiliary functions. But we had forgotten to check if the laptop control ports were compatible with the telescopes, and, of course, they weren’t. We’d have to drive back down the mountain on Sunday to the electronics store and then pray we could get them to work on Sunday.
But still, we could at least try to make sure we could do some basic things, like point to things in the sky.
We did a few daytime pointing tests and, to our sudden horror, realized that the telescope did not move the way it was supposed to. When we said go north, it went south. East was west. Looking carefully through the software we eventually realized that someone the telescope was confused about who it was. It thought it was its [bigger] sister telescope in southern Arizona. Somehow the control software had been switched. The sister telescope had enough different parameters (like which way was east and west) to know that this would never work.
Frustrated, we went to dinner with all of the other astronomers who were at Palomar for the evening, and we brainstormed about how we might fix things. By the end of dinner we had decided that no fix was possible; we needed the right software.
We were in luck, though. Another of my graduate students was awake and looking at her email and realized what we needed and, more importantly, realized where we the software was. We copied it over tested things out, and realized that we were in business.
Because the telescope was not actually ready to be used yet, we had to do some very low-tech things to get it to work right. First, we found nice bright Jupiter up in the sky. Then we used a hand paddle to get the telescope pointing in approximately the right direction. Then I stood up on a ladder, looking down the barrel of the telescope, trying as hard as I could to line up on Jupiter while Emily took continuous pictures with the telescope’s digital camera. We finally meandered around enough that we found it (it helps that Jupiter is so bright that when you get even moderately close to the right place you can see the glow off to one side). Once we were at Jupiter, the telescope was smart enough to know the rest of the sky, so we quickly pressed a few buttons and the telescope automatically slewed to where our occultation was going to be the next night. We weren’t sure how accurate the slew was going to be, but, to our surprise, the star that was going to be occulted was right there in the center just as it was supposed to be. This might work!
We spent the next 2 hours pretending like it was Sunday night and doing exactly what we were going to do that night. Everything worked well except for the occasional problem we had when we forgot that one thing not quite finished yet on the telescope is the dome control software. We had to move the dome by hand to following the moving sky. Sometimes we forgot. We vowed to do better the next night.
The next morning we woke up and drove down to San Diego to pick up some computer equipment. On the drive back up the mountain we looked up at the sky and groaned. Summer thunderstorm clouds had completely covered the sky while we were going. It was possible that they would abate as the sun went down, but they looked pretty bad.
We got back up to the telescope, installed the new equipment, tested it, and realized, again to our thorough surprise, everything was going to work perfectly. Before dinner time, we finally stuck our heads out of the dome to see what the sky looked like. It was hopeless. The sky was 100% covered, and the possibility of observing at all that night seemed very very remote.
We went to dinner in sour moods and lingered over our deserts longer than usual, knowing that looking outside was going to make matters worse.
But we were wrong. When we finally forced ourselves to look, the sky was miraculously clear. Not a single cloud. I have no idea how it so thoroughly cleared itself in under 45 minutes. We ran back to the 24-inch, opened the dome (we had closed it, fearing thunderstorms!), and waited for it to get dark enough to find Jupiter. As soon as it was visible in the twilight glare, we swung the telescope, pointed it up, and punched in the coordinates of the star. Again, on the screen, was just the right field. It looked pretty crummy though; everything seemed too faint. Ah! The dome! We turned the dome in the right direction and everything looked fine.
It was 8:30pm. The occultation was predicted to begin in an hour, so we started acquiring the data, meaning that we took a picture of the star every 4 seconds (which makes many many pictures of the star). At about 9pm clouds suddenly appeared north of where we were, but we quickly realized they were heading even further north. Still safe. At 9:20pm we took one final look outside: not a single cloud. We then crowded in front of the computer screen to watch our pictures come in. At about 9:26 we started thinking that the star was getting fainter. But really? We made some very rough instant measurements and thought: yeah. Maybe. By 9:27 we were sure. Every single image showed the star consistently fainter. It stayed that way for 4 full minutes before getting back to normal bright again. We had seen it! At 9:40pm we sent a quick email to the other astronomers who were observing around the country. The subject line was “Subj: Report from Palomar: We saw it!”
Over the next hour other reports came in. Many observatories were clouded out, but a handful got good data. A quick comparison revealed that Palomar had, I think, been right down the center, giving the longest of all possible occultations. An even more careful look at the data revealed that the occultation was certainly not sudden; we had without a doubt detected an atmosphere around this Kuiper belt object.
We went to sleep, exhausted but thrilled. Heading back we realized that the sky was 100% covered in clouds again. We had just snuck in some clear skies at the right time.
Enough people had collected good data that useful information would come out of these observations. We would get a nice measurement of the atmosphere and whether or not it has changed recently. Looking at the atmosphere was one of the main hopes of the observations. The Kuiper belt object is currently receding from the sun and many astronomers suspect that its atmosphere will soon freeze out. Of course, only the very largest few Kuiper belt objects even have atmospheres, but this one has been known to have had an atmosphere for a while. The Kuiper belt object we were studying was Pluto.

The great planet debate wasn't

Last week, in Baltimore, at the conclusion of a conference about planets and definitions, two astronomers faced off in what was termed the Great Planet Debate.
I missed the conference, and thus missed the debate, but, nonetheless, courtesy of a press release supplied by one of the participants, I can already declare a winner by default.
As I have said earlier, there is important science in classification, and that science is really not much of a subject of debate. Everyone can agree which objects in the solar system are dynamically dominant. Everyone can agree which are round. Everyone can agree which are rock or gas or ice. The only debate is about which of the many different important classification schemes should get to use that magical word “planet” to describe its members. And that debate is merely aesthetic, not scientific. So the “Great Planet Debate” is merely a debate about aesthetics, which I guess is OK, but, in my opinion, unlikely to be terribly Great.
But, according to the press release, the astronomer who was arguing against the current 8 planet definition wants, instead, to use a definition that says that anything round is a planet, and thus there should be 13 planets.
Suddenly there could be a scientific debate here, and this astronomer should be crushed. Everything round is a planet and there are thirteen round things? Where did that come from?
The planets would be the familiar Mercury through Pluto, for nine. Ceres, the largest asteroid, makes ten. Charon’s moon makes eleven, and my two discoveries, Eris and Makemake, make 12 and 13.
Regardless of your opinion of whether or not this is a fitting definition of the world planet, this is bad classification, and thus bad science.
So how many round things are there?
We don’t actually know the answer to that, since most of the objects in the Kuiper belt are so far away that we can’t see their shapes. Pluto and Charon have been measured to be round, so they count. Eris is assumed to be round because it is more massive than Pluto. Makemake has a poorly measured size and no known mass (it has no moon, which is the only way to measure a mass), but it is big, so probably massive, so probably round.
So what about other objects in the Kuiper belt? We can’t see them well enough to determine whether they are round or not, but we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round. The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn's satellite Mimas, which has a diameter of about 400 km. Several satellites which have diameters around 200 km are not round. So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round.

How many objects larger than 400 km are there in the Kuiper belt? We can't answer this question precisely, because we don't know the sizes of more than a handful of Kuiper belt objects, but, again, we can make a reasonable guess. If we assume that the typical small Kuiper belt object reflects 10% of the sunlight that hits its surface we know how bright a 400 km object would be in the Kuiper belt. Currently there are about 60 objects this size or larger in the Kuiper belt (including, of course, Eris and Pluto and Makemake), and one (Sedna) in the region beyond the Kuiper belt.

We have not yet completed our survey of the Kuiper belt. Our best estimate is that a complete survey of the Kuiper belt would double this number. For now, the number of known objects in the solar system which are likely to be round is about 70, with the number increasing as the survey of the Kuiper belt is completed.

Beyond the Kuiper belt there may be even more dwarf planets than in the Kuiper belt. Our best guess is that the region where Sedna resides could contain another ~2000 round objects.
So the victory in the Great Planet Debate goes, by default, to the 8 planet side. Whether or not you like the aesthetics of the 8 planet side, you have to disqualify the everything-round-is-a-planet side for thoroughly mangling the science of their own classification scheme. This is not to say that an 8 dynamically dominant planet definition is better than a ~70 round planet definition, but there can be no debate that an 8 planet definition is vastly superior to a 13 planet definition based on bad scientific classification.
How can this fundamental mistake have been made? Surely if you believe in the utmost importance of things being round, you would at least try to understand what was round and what was not, right? My speculation (some would say “paranoid speculation”) is that this was done on purpose. There is no doubt that the astronomer arguing the everything-round definition knows that there are many other round things. So why would he pretend there were not? Because, I suspect, he knows that arguing for 13 planets sounds more palatable than arguing for 70 planets. Arguing for 13 planets makes it seem like stingy astronomers are just being mean to the 4 being excluded. Arguing for 70 makes you seem a bit of an extremist.
There are good aesthetic arguments that can be made for the 70 planet everything-round definition. Make them! Argue them! Have a lively aesthetic debate! But don’t start by getting the science wrong. Particularly if it is being done on purpose.

Your Saturday Newspaper

I don’t know about other newspapers, but every week my local -- the Los Angeles Times -- devotes about a half a page to a few science stories. I love these, not just for learning a little bit about the universe around us, but also for getting a quick glimpse into the life of some scientist somewhere finally getting his or her paragraph of fame. This week: estrogen may ease psychosis; mummified fetuses from King Tut’s tomb are going to have their DNA tested, a hidden tribe of gorillas was found, virus can get sick from other viruses, and Antarctica used to have moss. Having a paragraph or two of your science appearing in your daily newspaper is both exciting – “my research is interesting to the world” – and depressing – “I spent two years on this project and all that makes the newspaper is that schizophrenic women should take estrogen.”
The route from doing research to that Saturday paragraph is indeed a long one, and one of the important steps after the research is all completed is publication of the results in the right scientific journal. Scientific journals are not all the same. Some are trade journals that specialize in a specific field (I publish much of my research in, not surprisingly, “The Astronomical Journal”) and accept most of the papers submitted to them (after a sometimes lengthy review and revision process). Others are more general with the implicit promise that the papers published there are more interesting, more important, and will get more notice. And, of course, it is much harder to get a paper published in one of these. Reporters know which journals are those top exclusive general ones, and so, when looking for stories for that Saturday column, they peruse those journals (and read press releases, presumably) and never bother with the trade journals.
The two top general journals in which everyone seems to want to get papers published are Nature and Science. If you start looking at those Saturday columns you will be amazed by how many of the stories come from papers published there.
Interestingly, though, along with publishing important ground-breaking papers appears to come the requirement that a larger than usual fraction of the conclusions published in these journals turn out to be incorrect. This leads to the semi-joking line that you often hear amongst astronomers: “Just because it is published in Nature doesn’t necessarily mean that it is wrong.” But it also leads to the real ambivalence that some feel for results published in those journals. People sometimes consider them to be flash and hype with no real substance and turn their noses up at the papers published inside.
I’ve been known to fall into this camp myself.
So it might be amusing to know that, tomorrow, my hope is to have a new paper ready for submission to Science. Why would I do this when I then turn around and scoff at others? Hypocrisy, I think is the answer. Or, as my friend Caltech oceanographer Jess Adkins likes to say: Nature and Science are the People Magazine of science. And like People, no one wants to admit to reading it, but everyone wants to be in it.
And so I submit.
The process is an interesting one. By tomorrow, I should have the full manuscript describing all of the results and with a few figures demonstrating important points and a slew of references to previous work all written in the precise format demanded by Science. I’ll log on to their web site and do all of the submission there. And then I’ll wait.
I think the rest of the process goes something like this (I may have some of the precise details mixed up here, but you’ll get the general idea). The paper will first go to an editor in the field of astronomy/planetary science who will decide whether or not there is even a chance that the results are interesting enough to warrant publication in Science. If the editor doesn’t think so, I will get a rejection notice within days. If the editor likes it, the paper will go to an editorial staff meeting with all of the other editors where it can again be voted up or voted down. I can again get that rejection notice (this one would be in, perhaps, two weeks).
If the editorial board likes it, the editor will send it out for peer review. The manuscript will get mailed to (typically) two experts in the field who will offer their detailed advice on the technical merits of the paper and whether or not it warrants publication in Science.
As is often said: peer review is a highly flawed system, but it beats all of the alternatives. It is easy to imagine some of the problems that could arise at this stage. A few that I have run across: reviewers who are competitor, reviewers who just don’t like you, reviewers who aren’t knowledgeable enough about your field. With only two reviewers for most manuscript, the process can be thoroughly random. The same paper sent to twenty different reviewers would get twenty different reviews. But, sadly, it beats all of the alternatives.
With luck, the two reviewers will like the paper and, with even more luck, suggest ways to improve the paper. They may point in flaws in the paper and how those flaws can be fixed. Or they may point in flaws in the paper and say they are not fixable.
If the reviewers don’t like the paper sufficiently that is the end of the line and you are rejected. If they potentially like it but with reservations you are given a chance to respond to their suggestions or complaints and modify the paper accordingly and then they get to review it again.
Finally, again, with luck, the editor send you that email saying the paper is accepted, and you sigh from relief. Or you get the rejection email, and you decide what to do next: another general journal? Reformat to go to a trade journal? Sulk in irritation for a while? I have done all of these and more.
The whole process can take a long time. If I submit the paper tomorrow, there is a chance that it might appear in your newspaper in, perhaps, January. Keep your eyes peeled to that Saturday section. But don’t look for an article on dwarf planets or on the Kuiper belt or on the early solar system. I’m taking a break from those this summer to pursue research on what I think of as my hobby field, Titan. Titan is a fascinating world with methane lakes at the north pole, dark dunes at the equator, a thick atmosphere that is almost like the Earth’s (it’s just missing a minor component [oxygen] that we like so much), and a Los Angeles-like haze that makes the surface hard to see. It’s my favorite body inside the Kuiper belt, and, when I get a little tired of studying the little points of light that make up the Kuiper belt, I move in to the relative warmth of the Saturn system and see what’s new on Titan. During my break this summer I think I discovered something pretty interesting. Interesting enough to be published in Science, even. But we’ll all have to wait to see if I can navigate that laborious publication paper and make it to that one paragraph in your Saturday newspaper.


Several readers pointed out that the correct Polynesian pronunciation of Make-make is not Maki-maki, as I suggested, but rather MAH-kay MAH-kay (where the capitals show accent). These readers are, of course, correct.

I find this mistake distressing as I spend so much time in Hawaii at telescopes that I think myself a proper Hawaiian-pronunciater. I can glance up at a street sign and read ten syllables in appropriate Hawaiian while my wife is still sounding through the first letters.

Hawaiian is easy. The "e" is always pronounced "ay". I get a demonstration of this every time I visit the summit of Mauna Kea to use the Keck telescope. Or when I just stay in the town of Waimea, where the Keck headquarters are. Or make sacrifices to Pele before observing (which, well, I admit to sometimes doing; she allegedly likes hard alcohol these days rather than virgins, being in shorter suppy).

But the first time I saw the name Make-make the wrong pronunciation just flowed out so easily (influenced, no doubt, by the Wiki-wiki buses at the Honolulu airport [wiki-wiki, meaning something like "quick quick." The buses are not particulatly wiki-wike, though]) that I never paused to get it right.

Sorry Make-make. And thanks to those who set me straight.

What's in a name? [part 2]

While a rose by any other name would surely smell as sweet, the Kuiper belt object/dwarf planet/Plutoid formerly known mostly as 2005 FY9 now smells a good bit sweeter to me after the International Astronomical Union has finally accepted our six month old proposal to give the object a proper name. The official citation reads:
Makemake, discovered 2005 Mar 31 by M.E. Brown, C.A. Trujillo, and
D.Rabinowitz at Palomar Observatory

Makemake is the creator of humanity and the god of fertility in the mythology of the South Pacific island of Rapa Nui. He was the chief god of the Tangata manu bird-man cult and was worshipped in the form of sea birds, which were his incarnation. His material symbol, a man with a bird's head, can be found carved in petroglyphs on the island.
Makemake, being of Polynesian descent, is pronounced Hawaiian-style (or at least what I think of as Hawaiian style), as “Maki-maki.”
Three years is a long time to have only a license plate number instead of a name, so for most of the time, we simply refered to this object as “Easterbunny” in honor of the fact that it was discovered just a few days past Easter in 2005. Three years is such a long time that I think I’m going to have a hard time calling Makemake by its real name. For three years we’ve been tracking it in the sky, observing it with telescopes on the ground and in space, writing proposals to observe it more, writing papers based on what we see, and, all the while, we have just called it – at least amongst ourselves – Easterbunny. If you came in tomorrow and told me that from now on my daughter – who also just turned three – was to suddenly be called something new, I would have a hard time with that, too.
Nonetheless, I’ve been waiting for Makemake to get a name for a long time, so I’m going to walk in to my regular Monday morning research group meeting tomorrow, pour a cup of coffee, and casually tell me students that I am working on a paper on the detection of ethylene ice on Makemake. My students, who will probably not yet have heard the word that the name is out, will look at me a little blankly, shake their heads, and proceed to ignore me, as they often do when I say things that make no sense (which, they would claim, happens weekly in these meetings). But then I’ll tell them: 2005 FY9, Easterbunny, K50331A (the very first name automatically assigned by my computer once I clicked the button indicating that I had found it; 5=2005, 03=March 31=date A=first object I found), will henceforth be know solely as Makemake, the chief god of the small Pacific island of Rapa Nui.
We take naming objects in the solar system very carefully. We’ve picked out the names for Quaoar (creation force of the Tongva tribe who live in Los Angeles), Orcus (the earlier Etruscan counterpart to Pluto, for an object that appears much like a twin of Pluto), Sedna (the Inuit goddess of the sea, for the coldest most distant Kuiper belt object at the time), and Eris (the greek goddess of discord and strife, for the object that finally led to the demotion of Pluto). Each of these names came after considerable thought and debate, and each of them fit some characteristic of the body that made us feel that it was appropriate.
Coming up with a new permanent name for Easterbunny was the hardest of all of these. Orcus and Sedna fit the character of the orbit of the body. Eris was so appropriate it is enough to make me almost start believing in astrology. Quaoar was, we felt, a nice tribute to the fact that all mythological deities are not Greek or Roman.
But what for Easterbuuny? It’s orbit is not particularly strange, but it is big. Probably about 2/3 the size of Pluto. And it is bright. It is the brightest object in the Kuiper belt other than Pluto itself. Unlike, say 2003 EL61, which has so many interesting characteristics that it was hard choosing from so many different appropriate name (more on this later), Easterbunny has no obvious hook. Its surface is covered with large amounts of almost pure methane ice, which is scientifically fascinating, but really 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 trance-like 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 names) after whom Easter is named, until I later realized that this mythology is perhaps mythological, and, more importantly, that an asteroid had already been named after this goddess hundreds of years ago. Strike two.
Finally 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 spent a while considering “Manabozho” an Algonquin rabbit trickster god, but I must admit, perhaps superficially, that the “Bozo” part at the end didn’t appeal to me. There are many other rabbit gods, but the names just didn’t speak to me. Strike three.
I gave up for about a year. It didn’t matter anyway, as the IAU was not yet in a position to act, and I was still waiting for them to decide on a proposal for 2003 EL61 which I had made 18 months ago (again, more later).
This Christmas, though, it was suggested to me that there were rumblings within the IAU that perhaps they would just chose a name themselves and not worry about what the discoverers thought. One could say that this should not matter and I should not care; there is no science there, after all, but, I enjoy, take seriously, and spend way too much time on this giving of names. I was not interested in a committee telling me the name of something I had discovered. So I went back to work.
Suddenly, it dawned on me: the island of Rapa Nui. Why hadn’t I thought of this before? I wasn’t familiar with the mythology of the island so I had to look it up, and I found Make-make, the chief god, the creator of humanity, and the god of fertility. I am partial to fertility gods for things I discovered around that time. Eris, Makemake, and 2003 EL61 were all discovered as my wife was 3-6 months pregnant with our daughter. Makemake was the last of these discoveries. I have the distinct memory of feeling this fertile abundance pouring out of the entire universe. Makemake was part of that.
Oh, and Rapa Nui? It 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 better known by its English name of Easter Island.