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.

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.


  1. I think any talk of "nails in the coffin of Pluto as a planet" is highly premature, as can be seen from the continuing controversy over this issue. Instead, many see you as having discovered a whole new subclass of planets alongside Pluto.

    I'm sorry to hear you won't be involved in future planet hunting, as I can't wait for the discovery of a Mars-sized object in the Kuiper Belt that will likely force the IAU to realize the absurdity of its planet definition, in which the same sized object is a planet in one area and not a planet in another.

    Meanwhile, don't count Pluto out just yet.

  2. Well, "planet killer", congrats for a most deserved rest. You and your team have certainly made astronomical history - have no doubts.

  3. Poor Pluto. If the second generation camera did not detect a Trans-Neptunian Mars, that means that such an object must be on a highly inclined or eccentric orbit like Sedna. A highly eccentric orbit would mean that the object is currently too far away and too faint to be detected. Sedna varies from an apparent magnitude of 20.4 (perihelion) to about 35 (aphelion) depending on where it is on its orbit. It does not look like a Super Pluto is going to come save Pluto's status any time soon.

    Mike how far from the ecliptic did your 2nd generation search extend?
    -- Kevin Heider

  4. Pluto's status does not need to be "saved." Finding a Mars-sized object in the Kuiper Belt would hasten awareness of how ridiculous the current IAU planet definition is, but it is not necessary for that definition to be overturned or at least amended to include dwarf planets as planets. So sorry, Mike, posterity may see you not as a "planet killer" but as a "planet discoverer" several times over.

  5. Hi Kevin,

    the problem of a dwarf planet father out is not the brightness, but its slow movement. So there is a high chance that the missing dwarf planets are already photographed plenty of times but regarded to be distant faint stars. Mike's method can detect dwarf planets until about 120 AU (see http://www.gps.caltech.edu/~mbrown/papers/ps/xena.pdf, section 2 discovery); maybe the last survey of Mike reached out farther.

    Regards, Ralf

  6. Any of you who may live in the Los Angeles area might have noticed the quite strange weather the last two night. Rain. Thunder. Lightning. The telescopes on Palomar have all been closed. Me? I went out for a walk with my daughter in the warm rain falling at sunrise and told her how wonderful it was when water falls from the sky. And I didn't think about planets at all.

  7. Kevin, Ralf --
    Our 2nd survey went approximately +/- 20 degrees from the ecliptic and was sensitive out to 1000 (!) AU (but only to really absurdly large things at that distance. We could have seen Mars to ~200 AU).

  8. In the solar system we have asteroids that act like planets (Pluto, Eris, etc.), asteroids that act like centaurs ((44594) 1999 OX3), centaurs that act like comets (2060 Chiron), and comets that act like asteroids (14827 Hypnos and main-belt comets).

    Natural objects do not strive to fit our discrete, comfortable classifications.
    -- Kevin Heider

  9. Hi, Mike :)

    Congradulations on the historic completion of your initial survey. What I am wondering is what effect this will have on your blog, here. We now have some very solid science to work with. Is it OK to speculate on your blog? I would think that this is actually the time for such things. "Planethood" status has been argued until we're all blue in the face, so maybe it's time to expand and start asking questions about what we know and what we migh look for now that there will probably not be any major surprises.

    This brings up catagories (!). There is "theory", which has largely been proven, but some people's "theories" are other people's speculations. I started my tour of astronomical exploration because I thought large objects formed at Lagrange points throughout the Solar syatem and when I started this was, of course, speculation, not even a hypothesis. But as information became available I have come to think of this as more mainstream; Dr. Edward Belbruno of Princeton and several others accept this now at least in the case of Earth's moon. Similarly with a lost moon of Triton; Drs. Craig Agnor and Douglas Hamilton have advanced this idea. As far as I'm concerned, these two points are now "theories" although I realize the general public might not think so.

    Then there are "hypotheses". My hypothesis is that Haumea is the lost moon of Triton. Completion of your initial survey tends to eliminate unknown competitors from showing up, so this moves closer to being a "theory". I'm pretty much convinced but more work needs to be done on this.

    I have gotten as far as passing Calculus III, but would need additional courses in differential equations and vector calculus, plus probably a few other courses in advanced mathematics to more fully understand my own theories.

    Meanwhile, other instruments besides telescopes have become available to amateur astronomers. I use a program called "GravitySimulator" to explore my own little niche in astronomy. There are other programs, for instance I test-drove Douglas Hamilton's "Integrator" and it was awesome, like comparing a moped to a Ferrari. Still, most amateur astronomers have, like, 8" telescopes. I have little time these days to do GravitySimulations because I am working towards an actual education. GS is fun, like a video game (difficulty level somewhere between "Joust" and "Robotron", about equal to "Defender") and you can use it to make important discoveries, but those need to be followed up by actual calculus. Real calculus is expensive, especially in terms of time needed to study it.

    Work with the GravitySimulator has indicated that there is in fact a much larger Solar system object out there, but it's much larger than Mars or even Jupiter, GS indicates at least three Jupiter masses. This comes from examining what our Kuiper Belt looks like and concluding that it has been damaged by a massive object. Examination of the infrared signatures of other stars tends to back this up. GS was able to set an extreme lower limit for this object of 3 Jupiters. Observationally, if such an object were larger than 45 Jupiters, existing surveys would have detected it.

    The idea of such an object follows the "Nemesis" theory, and this has tended to get a bad reputation as "Niburu" and "Planet X" people have distorted it with pure invention. One can be fooled there, though; I thought that the "Monte Carlo" method of determining a periodicity for mass extinction events on Earth might be an invented mathematics, but after entering school I have discovered that this techique is well-accepted and so Raup, Sepkoski, Muller, and others need to be taken more seriously.

    In conclusion I do have a serious question as to how far you will allow speculations to go on your blog. I do know that on other forums any discussion of any "Nemesis" immediately brings hoots and hollers and comparisons with ideas that are REALLY speculative; but then there are plenty of pointless political arguments on such forums, also.

    So, how far can we go?

    Thank you,

    Michael C. Emmert

  10. Our 2nd survey went approximately +/- 20 degrees from the ecliptic and was sensitive out to 1000 (!) AU (but only to really absurdly large things at that distance. We could have seen Mars to ~200 AU).

    Hi Mike,

    So if there were, say, a Sedna or Eris sized object beyond 200 AU (or less), would your recently completed survey have been able to detect such an object?

  11. Hi, Ralf :)

    "Hi Kevin, (ditto),

    the problem of a dwarf planet father out is not the brightness, but its slow movement."

    In that case we would replace movement as a criteria with parallax. Two pictures of the same part of the sky are taken about six months apart, less a little for practicalities such as avoiding the horizon, etc, and are compared. This gives a different angle to each photo so close objects stand out. Parallax is movement, of course, but it's movement of the Earth rather than the objects you are trying to detect.

    I'm interested to see if there are any remnants of ojects beyond 50 AU. Of course, it would be kind of frustrating to get a null result from this kind of observing program, but that would be a very important result that would tell us a lot.


    Michael C. Emmert

  12. It's been wonderful Mike. I have been following your discoveries since 2005 and have felt very privileged to watch a chapter of astronomical history unfold within each story of your individual discoveries.

    Will you continue to blog?? You have a wonderful gift for story telling. As an amateur astronomer I really appreciate reading them. It is great to watch people find planets as I too have always dreamed of finding one my self!

    Thank you so much, your work is inspiring.

  13. Hello Mike,

    "Our 2nd survey went approximately +/- 20 degrees from the ecliptic and was sensitive out to 1000 (!) AU (but only to really absurdly large things at that distance. We could have seen Mars to ~200 AU)."

    When I interprete the numbers right your second survey would not have discovered Eris (Aphelion and 44 degrees), Makemake (nearly Aphelion, 29 degrees) and Haumea (nearly Aphelion, 28 degrees) and also Orcus would have been just on the borderline .......

    Thus I think a further thorough survey seems to be required for better understanding of this very interesting region and I hope that the financial means will be approved for this.

    Regards, Ralf

  14. Hi Mike,

    Given that Sedna spends just 2% of its orbital time within your detectability limit, the principle of banality dictates that there should be 100%/2%= about 50 Sedna-like objects (sednoids?)(I mean objects with similar elongated orbits, and similar sizes, not pebbles).
    Given too you put the limit of your recent survey at a Mars (H=-1.52) at 200AU, that would mean that in the 25% of the celestial vault that you have scanned, you did not detect:
    * any object with abs mag smaller than Sedna's(H=1.57) beneath 98 AU (comparable to current Sedna's distance at 90AU)
    * any object with abs mag smaller than Haumea's (H=0.2)beneath 135 AU
    * any object with abs mag smaller than Eris'(H=-1.2)beneath 185 AU
    * any object with abs mag smaller than Earth's(H=-4)beneath 360 AU
    * any object with abs mag smaller than Jupiter's(H=-8.5)beneath 1000 AU

    This still leaves plenty of hopes!

    Congratulations for all your discoveries.

  15. I placed three videos about ancient wisdom of our Solar system, Kuiper belt, Oort cloud,Planet X,...on Yotube.
    If you want to see more detail about those patterns,..there is my web hamops1.szm.sk, where are mentioned also other my webs,...Some patterns from that source are on many Turkish, Iranian,...carpets, but you can see those "windows" also in proportions, shapes,..of gotic cathedrals, orthodox, islamic,...churches. There is older book of Fulcanneli-Secret of cathedrals, where those architectonic secrets tied with solar system, with even Planet X were partly described or foreshadowed,...

  16. Hey, wait a sec! I was assuming "The End" meant the end of this phase of your career. Did you also mean the end of updating your blog? I hope not!

  17. no, no. just taking a bit of a break to do a little science (and committee work). stay tuned for this weekend!

  18. The release of the exoplanet images today must have been at least as exciting for you as it was for anyone. Have the possibilities of discovery of planets and so-called dwarf planets in our own system been pretty much exhausted?