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.

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.


  1. Very nicely said....
    Something more on this particular picture, is that it is of a fairly easy to find star in the sky. This lets me (a planetarium presenter) tell the laymen that hey, we have a picture of a planet around this particular star. It's one thing to say (and we do) that we have found lots of planets around many stars, but another to say that we see a planet around Formalhaut.
    I'm going to enjoy pointing that out at the next star party as well. Lots of people have no idea that we have found a lot of exoplanets, this gives me a good visible reason to talk about them.

  2. Mike, I agree it is important to be excited despite the inevitability of the discovery. It is a major landmark on the way to developing a full catalog of the planetary systems around us. That one of the discoveries was made by Hubble, which (I assume) was not designed with exoplanet hunting in mind, makes it even more remarkable.

    Outside the bounds of our solar system, this type of discovery is the future of space exploration for at least the next century or two or three, so it's vital to keep the public engaged in the support of the planet-finding missions ahead.

    While it might not be much need for a Hitchhiker's Guide to the Galaxy yet, it is certainly high time we start to compile the Encyclopedia Galactica.

  3. >>> yes, these really were the first images of planets outside of the solar system

    Really ? And what about this one ?


  4. Hi, Mike :)

    The search for extrasolar planets is a fascinating story. It is, of course, a major acheivement of the intellect of man. I think there's a good object lesson in the history of the detection of these objects of our curiosity.

    Most extrasolar planets have been discovered by the Doppler shift technique. Doppler investigated this by, among other things, hiring a band to play on a passing railcar. Geoff Marcy and Paul Butler made the invention that made detection of other stars' planets possible. They ran the light of the star they were examinig through a gas cell to absorb certain frequencies and print a calibrated stationary spectra on the star's spectrum so that the Doppler shift could be measured accurately.

    They tried all kinds of gases in the cell, including a deadly WWI nerve gas, which was rejected for obvious reasons. When it was finally perfected, they published it. And they started looking for the extrasolar planets. Their method was very sensitive and they could detect analogues of Jupiter and Saturn so that's what they looked for.

    Didier Queloz and Michel Mayor picked up on the invention and set about discovering whatever showed up. One day they stepped back to look at the whole program and asked themselves, "What if there's a large signal?". They realized that their data analysis technique would miss a large signal, so they fixed that and promptly discovered several extrasolar planets.

    Marcy and Butler were stunned. They had been scooped! All that work and a simple adjustment caused them to lose the discovery of the first extrasolar planet. And they had invented the technique!

    So, of course, had Doppler.

    The "hot Jupiters" or "roasters" were a very important discovery that gave a disturbing answer to a mathematical problem that had vexed Laplace. Are solar systems dynamically stable? Laplace published a book-length proof that our system was, but later a graduate student went over it and discovered an error that invalidated the whole proof.

    The discovery of roasters and the high eccentricity of the known extrasolar planets is powerful evidence that solar systems are not neccessarily dynamically stable. Such a thing makes extrasolar life less probable.

    There's an observational bias here, though. You have to follow a planet through two orbits to prove that it's a planet using the Doppler technique. A randomly located alien astronomer using the same equipment would take 24 years to discover Jupiter and 52 years to discover Saturn. There's no way to rush it. So we won't know where the Sun fits in the statistical analysis of the prevelance of Solar type systems for at least 52 years.

    I don't think Queloz and Mayor should be castigated for a "rush to publish" because of the extreme importance of getting observational results for the stability problem. This was a vitally important discovery. As for being half the story, we won't see the other half for years so we should enjoy the existing discoveries now for all they're worth. The rest will come later.

  5. "It became a big deal culturally, as it precipitated the long-discussed downfall of Pluto..."

    This "downfall of Pluto" thing itself is bad science. Sorry, but you haven't killed Pluto as a planet; the scientific arguments for keeping it as one are alive and well, as can be seen here: http://www.sciencenews.org/index/generic/activity/view/id/38770/title/Debates_over_definition_of_planet_continue_and_inspire

    Here's a suggestion from a writer. When talking to reporters, how about being honest when discussing an issue still very much under debate as opposed to portraying one side as the only view and the issue as a done deal, when it is not.

  6. Hi, Laurel :)

    I went to the link you provided and I see it is by S. Alan Stern, Principal Investigator for the New Horizons mission to Pluto. And he does give us this piece of honesty: "I myself am a partisan in this debate." I guess there are some of those still around. Dr. Stern had a tough fight getting funding for his spacecraft and felt that calling Pluto a planet would help him in that regard. There were $650,000,000 at stake and a bunch of jobs so I suppose one can't get too hard on him for that.

    He's got a point, though, from looking at the dynamical disasters we've discovered so far it is beginning to look like in other solar systems, some planets clear other planets out of thier orbits. It looks like roasters are clearees, so do you not call them planets because they lost the orbital dominance food-fight? Most likely in these cases the other object got thrown out of the system to journey through cold space alone. Such a thing would truly be a "wanderer", which was the original Greek definition of a planet.

    I like the classification system used in our own Solar system right now just fine. Pluto is a "clearee" so it fits in an entirely different classification than Jupiter. But I must admit that kind of falls apart when viewed in the light of exoplanetary discoveries.

    Right now, with the serious observational biases of exoplanet surveys, it's kind of early to establish any kind of classification scheme for these objects. In the meantime, I think the IAU definition makes it a lot less confusing when talking about places closer to home.

  7. mikeemmert: Which classification scheme are you referring to when you mention you like the one being used for our solar system now? My point is that there isn't only one classification scheme currently in use--there are several competing ones. I'm not sure what you mean by a "clearee," but my point is that there are many planetary astronomers who use the criterion of hydrostatic equilibrium as the determining factor in whether or not an object is a planet. Yes, Stern is partisan, but so is Brown, so are all who have studied this issue and take strong positions on it. That is my point. New Horizons is already launched, so it doesn't make sense to attribute Stern's position to funding and jobs. I heard him speak at the Great Planet Debate in Laurel, MD, this summer, and it's clear he genuinely believes in hydrostatic equilibrium, and the resulting geological processes and differentiation it causes on celestial bodies such as Pluto, as the defining factor in determining what is a planet.

    I disagree that the IAU definition makes things much less confusing when talking about our solar system. No one would put Jupiter and Pluto in the same class regardless of the orbit clearing issue. In fact, Earth is much more similar to Pluto than to Jupiter. We can easily distinguish the 13 planets in our solar system (under the hydrostatic equilibrium criteria) by dividing them into terrestrial planets, gas giants, ice giants, and dwarf planets. The IAU definition makes things more confusing because it says that dwarf planets are not planets at all, defines objects solely by where they are rather than what they are (Earth in Pluto's orbit would not be considered a planet), and uses the fuzzy term "clearing the neighborhood of its orbit," which if applied literally would preclude every object in our solar system, including Jupiter, from being classified as a planet.

  8. Hi, Laurel :)

    The classification scheme I'm refering to is the IAU classification where there are eight major planets in our Solar system. They cleared their orbits because they were massive enough to do it. A "clearee" is one of those objects that got cleared out of another planet's orbit. Pluto got cleared out of Neptune's orbit.

    Yes, there are a lot of planetary classification systems out there, if you remember the old TV serial "Star Trek" had one of those. At the time it was believed that the Sun was a typical star and that other stars must have planetary systems similar to our own and that life must be very common in the Universe. So planets were classified according to what kind of life-forms populated it.

    That classification system is no longer used. But they are still showing reruns. And people are still enjoying them even though modern cellphones are much more capable and flexible than the then-novel communications devices depicted on the show.

    I would like to point out to you that the IAU is still calling Pluto a planet, except they add the term "dwarf" in front of it. I don't see a problem with this, after all, Jupiter, Saturn, Uranus, and Neptune have been called "gas giant" planets for as long as I can remember. At least they didn't tack on "ice" in front of "dwarf".

  9. Hi, Mikeemmert,

    I don't think the Star Trek example is comparable when discussing a planet classification system currently in use. Star Trek is fiction--although some astronomers have suggested appropriating its method of distinguishing among planets.

    In contrast, there are several planet classification schemes in use today by real astronomers (not in fiction), and the IAU definition is just one of many. Describing it as the only current one is misleading.

    According to the IAU definition, dwarf planets are not planets. If it were as you say, the definition would make a lot more sense. However, resolution 5b at the 2006 General Assembly, which would have included both classical planets and dwarf planets under the umbrella of planets, failed by 333-91. As a result the official IAU definition precludes dwarf planets from being classified as a subcategory of planets. This is a major reason why the IAU definition is so problematic.

  10. Mike, loved this post. Sorry the comments turned into a "what's a planet?" debate.

    Your final thought was enlightened. I've gotta know, did you think of that on the spot or were you holding that one in your head until the perfect moment?

    I'd also love to know what's the worst that a reporter has quoted you? :o)

  11. Howdy all :)

    I just read an exciting result this morning about exoplanets:


    It's called, "Odd planet's extreme global warming: Highs of 2240". It's about a strange planet in the Big Dipper called HD80606b. It has a very eccentric orbit which alternately takes it very close to it's star, then moves fairly far away. So it is alternately broiling and, well, not freezing, but cooler.

    There's a bit of hype in the headline on this. People are interested in global warming here on Earth so the reporter decided to tie this story in with that. Obviously HD80606b have weather and climate totally unlike that of Earth's.

    What we can see as visible here (and the research was done with the Spitzer telescope, which actually views infrared) is the result of changing light levels from the star, which goes to surface heating. That's a point of similarity with Earth for sure. But the high eccentricity and close proximity to it's star should be heating the planet throughout it's bulk due to tidal forces.

    Here's a quote from the story that shows why it is Breaking News:

    "The star is visible from Earth near the Big Dipper. On Feb. 14, HD80606b will travel between the Earth and its star. There's a 15 percent chance that amateur astronomers using small telescopes could see it swing by, obscuring a tiny part of the star, Laughlin said."

    This lucky accident of aligning a planet with it's star gives amateur astronomers a chance at making a contribution. We can find the diameter of this planet, which (since it's probably a gas giant planet) can give us some idea of how hot it is in the interior.

    There's one good thing about "license plate numbers". The lower case "b" in HD80606b tells us that there are at least two planets in this system. That's the only reference to this fact in the article.

    License plate numbers for dwarf planets at this time tell you only the date of discovery. It takes luck for these acronyms to make a pronouncable word, like 1992 QB1 which lent it's name to "cubewanos".

    With the chaos visible in this new system, I am beginning to fear that chaos rules in the Universe as a whole and that most other systems may be so chaotic that any kind of classification system is doomed :0 .


    -Mike Emmert