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 redemption of Snow White (Part 2)

(read Part 1)

One of the nicest things about science is that, usually, when you’re wrong  you’re just wrong.  There is no use sitting around arguing about it or trying to persuade someone to change his mind, you’re just plain wrong and the universe has explained it to you. Game over. Thanks for playing. Try again later. Next?

Only there really was no “next.” Red? For the most part, colors of objects in the Kuiper belt are relatively mysterious, so there wasn’t much of story there. Snow White remained nicknamed Snow White, despite the now obvious inappropriateness of the name, but it mostly became known as a moderately large object in the Kuiper belt that didn’t have a real name. As I mused in this space 2 1/2  years ago, Snow White needed a bailout. By which I meant, we needed to find out something interesting about it or it was never going to be worth talking about, much less naming. As I said back then, "Snow white? Well, it’s just a big Kuiper belt object."

And then something really interesting happened: Snow White got brighter.  While observing a slew of Kuiper belt objects at the Keck observatory two years ago, we swung the telescope around to Snow White and were shocked to find out that it was almost two times brighter than we had expected.

Kuiper belt objects don’t suddenly get brighter without a cause (in fact, nothing in the Kuiper belt ever had gotten brighter before). Was it like a giant comet that had suddenly gone into outburst? If so, it would have been – by a large margin – the most distant active comet ever seen and – by a larger margin – the largest. What if, instead, something happened on the surface? A frost formed which reflected more sunlight? Nothing like that had ever been seen before, and it didn’t make a lot of scientific sense, but we have found stranger things. What if, instead, a huge impact on Snow White dispersed a cloud of dust that was reflecting extra sunlight? That would be a shock with Snow White so far in the outer reaches of the solar system where there is almost nothing else around.  So what could be going on?

Having the chance to discover something truly exciting like this is one of the reasons that being an astronomer is so much fun. You’re presented with something that doesn’t make sense at all and suddenly you have to figure it out from scratch. No running to Wikipedia to look it up. No asking someone else. It’s just you and the universe staring each other in the eye and seeing who will blink first. And, in my decades in the field, I have found that the most likely explanation to a truly exciting and unexplainable observation is that it’s just wrong.  Which, in this case, it was.  The universe refused to blink.

In this case the answer wasn’t that our Keck observations were in error, but that Snow White had actually been bright all along, and we just hadn’t realized it from the discovery observations. When you’re out searching vast areas of the sky night after night looking for objects in the Kuiper belt, you observe in all kinds of conditions and all kinds of weather. If you waited just for the times when everything was perfect you would cover much less sky find many fewer things and have a lot less fun. On the night when Snow White was discovered, conditions were relatively poor, so it was impossible to measure precisely how bright the newly discovered object was. We had to make an estimate, like we had had to do many time before. Our estimates had always been within about 30% of the correct value. This time, though, because of the conditions and the location in the sky, our estimate was off by a but more. Even these miss estimates usually don’t matter,  as we do follow-up observations later (to track the object to find its orbit) which usually give a much better estimate of the brightness. In the case of Snow White we did the follow-up observations, but conditions even then were bad enough that we never got a better brightness estimate. By the time we got to the Keck telescope, a year had passed, and we had still never gotten a precise brightness measurement, so we were startled at how bright the thing really was. Going back to try to re-calibrate the old data, though, we can see that it was likely that bright all along.

We suddenly realized that Snow White was not just a moderately bright moderately interesting Kuiper belt object, but was actually the 5th intrinsically brightest object known (by which I mean: if you put all of the objects the same distance away from us, Snow White would be 5th brightest, after Eris, Pluto, Makemake, Haumea, and Sedna).

Snow White was looking more and more interesting. The next step would be to obtain a high-quality infrared spectrum of the sunlight reflecting off the surface. Such a spectrum might be able to tell us what was on the surface and thus why Snow White was so bright and why it was so red. We had been doing that sort of spectroscopy of faint objects in the outer solar system for most of the past ten years using an instrument called NIRC (which cleverly stands for near-infrared camera) on the Keck telescope. NIRC was the best Kuiper belt spectrograph in the world, and it had helped with a decade-full of discoveries (ammonia on Charon, the Haumea collisional family, the unusual surface of Makemake, among others), but it had just been retired after 15 years of heavy rotation at the summit of Mauna Kea. 

After a decade of having the best window into the surfaces of Kuiper belt objects, the shades were suddenly closed and we were blind. Snow White became not just the largest object in the Kuiper belt with no name, it also became the largest object in the Kuiper belt whose surface was – and seemed destined to remain  – a mystery.
Go on to Part 3.


  1. I love your stories about science unfolding. How I Killed Pluto (And Why It Had It Coming) was the first book I ever purchased for my Kindle, and I couldn't have picked a better book. Your enthusiasm for your work is infectious. You manage to convey the drama of your discoveries while simultaneously showing that it is a career, similar to many people's, and that parts of it are a slog, just like everyone else. Equal parts excitement and humility keep me coming back for more. In short, I'm glad you're getting back into the swing of blogging. Keep up the good work.

  2. I said in my previous comment: 'but magnitude remains the same'. Well it usually does... but it's not even the case here. So red (darker) and with quite greater apparent magnitude than expected... how big is Snow White?

    I'm expecting something like in the range of Eris but I'm not really good with the maths involved, so I'll have to wait for the final post, I guess.

  3. You ARE a good writer, Mike :D A mark of a good writer is the punchline.

    This brings up a couple of questions, though. One, how much of the sky did your survey miss because of clouds & etc? Surely there are patches of blankness somewhere. I know this because the Perseid meteor shower comes tomorrow morning, and I have the most terrible luck with meteor showers and clouds. Looks good for tomorrow, though.

    Another has to do with the Kepler and WISE missions. Kepler announced a data release and then said there would be a more comprehensive release "later". All the reporters in the room howled with frustration. WISE did the same thing, promised a data release in May, then moved that up to April, then released only RAW data. Very frustrating seeing as my computer is burnt out and I can't examine it myself. They have not announced ANY "magentas" (my name for objects 1-13 mJ because according to J. Davy Kirkpatrick that's what color they are) within the ten light years it can see them, and I am virtually certain that there MUST be a magenta within that distance.

    The above paragraph is about being wrong. Maybe I'M wrong, as you know I've made some public predictions. If one is wrong, then one must set aside a period to agonize over it. Let's face it, it's a hard thing.

    It's even harder not to KNOW whether you are right or wrong. Now the date is set back to March 2012. I realize that some very important announcements need to be gone over carefully to make sure it's not a piece of lint on the lens or some cloud in the corner. Still, I feel like the old vulture cartoon, "Patience my eye, I'm going to KILL something!" (Besides, I have funding agencies that want to KNOW. Right NOW. They would not understand your articla at all.)

  4. Hey Mike,

    Is your team sifting through any WISE mission data?

    If so, can you give any hints on outer solar system body discoveries that might be suggested in the data?

    Thanks, John

  5. A question: has anyone followed up on 2002 UX25 or 2003 AZ84 since their moons were discovered?

  6. Dear Mr. Brown:

    L.T.N.S., glad to hear from you again.

    Thankfully you will not be "blinded" for long as the EELT is under construction in Chile, to replace the worn-out Keck telescope, which hopefully will last as long as the Keck.

    Although I must say as an ignorant outsider, that it seems a tad strange that in the day and age of digital this and that, that we would have to keep building larger and larger "conventional" visible light telescopes; just much larger and more sophisticated versions of telescopes invented in the 17th century.

    Eventually, astronauts in space will be able to shave themselves by looking at the Super Ginormous Telescope (SGT) mirror on Earth.

    It is interesting, but not seemingly surprising, to discover that an object can become brighter, i.e. if you put break the capsules within a glow stick it start the chemical reaction that causes the sticks to glow, gradually the sticks will become dimmer over time. However, if you place the spent sticks in a freezer, that not only glow again, but become much brighter.

    Other possibilities for changing brightness (not necessarily regarding Snow White):

    Perhaps frozen or as in the case of Titan, liquid bodies (lakes, rivers, oceans) could cause the reflectivity to change as the world rotates, orbits or changes seasons.

    It is possible for an icy crust to melt from geothermal forces including vulcanism.

    Perhaps the surface could be blanketed with rocks or minerals, like obsidian or quartz here on Earth, that have a reflective (naturally polished sheen) surface.

    It could actually be a chunk of ice, covered in a mottled fashion, with a thin layer of oxidized dust, such as rusty iron, making it appear both reddish and brighter than other nearby objects.

    Cryovolcanism could cause reflective ice crystals to be blasted into a world's atmosphere as on Titan or blasted into space, then fall to the world's surface which occurs on Enceladus and Io.

    But whatever the case, interesting yes, surprising, no.


    George Smith-

  7. Is it possible, however unlikely that Snow White could have an atmosphere? If it has volatiles within, like a "dwarf planet/comet," but instead of having a tail, it has an atmosphere, even a thin one could in theory, have reflectivity and double the brightness.

    Perhaps red dust, common in the area of our Solar System, has settled onto this dwarf planet/comet, which would explain its red color.

    Perhaps Snow White should be renamed Snow Red, Red Snow, Little Red Riding Hood (in honor of Lilah) or Cherry Snow Cone???

    George Smith

  8. the sun is pretty bright, but I guess there must be an out in the definition of "intrinsically"

    Paul W. to Wyoming

  9. Oh god, not again with the naming things after Lilah. The only objects that can be named after living people are main belt asteroids, and only by the discoverers. Let's stick to mythology.

  10. Hi Mike, there wasn't longer time your amendment about global weather changes on your favourite moon Titan. Such strange arrow shaped storm or what it could be there wasn't yet,...
    There are suddenly too many very expensive cosmic ray detectors in space, !? Results from Milagro were officially not interesting,....gha, uf,mh,..
    Pavel Smutny

  11. Dear Anonymous:

    Mr. Mike Brown was the one who came up with the (nick)name of Snow White and is just a friendlier moniker in lieu of 2007 OR10; it is not its official name.

    But since the nickname "Snow White" does not even reflect the characteristics of the world, how is one to propose an official one?

    So relax, take a chill pill and wait for more information to be gathered about the individual attributes of this newly discovered world; only then could a mythological name be considered.

    Original message being responded to:

    Anonymous said...

    "Oh god, not again with the naming things after Lilah. The only objects that can be named after living people are main belt asteroids, and only by the discoverers. Let's stick to mythology."

    August 15, 2011 10:16 PM

  12. " ... Snow White would be 5th brightest, after Eris, Pluto, Makemake, Haumea, and Sedna ..."

    Hum ! The 6th one at my count !

    About drawf planets candidates size, stellar occultations is a nice measurement method.
    Waiting 2007 OR10, Makemake & Quaoar results (5 chords each) will be available in october ...

  13. Mike:

    I can't wait to see Part 3. The more I learn about these dwarfs, the more fascinated I am by them.

    On a related note: I've found your nifty "How many dwarf planets" page (http://www.gps.caltech.edu/~mbrown/dps.html) via Twitter, but can't find a link on your main Caltech page. Am I missing something?

    Final note: I just finished reading "How I Killed Pluto" (practically in one sitting), and give it two thumbs up. The part where you're doing statistical analysis on Lilah's feeding times -- while simultaneously dealing with the unplanned announcements of the discoveries of Eris, Haumea and Makemake -- really made me laugh.


    Bob Shepard of Denver

  14. vagueofgodalmingAugust 18, 2011 at 3:11 AM

    I agree with George Smith: there's nothing so redemptive as a silly public naming competition.

  15. Has anybody suggested Horton (of Who fame) yet?

  16. This article about Mike and "Snow White" and other dwarf planets was published today over on Science Daily, http://www.sciencedaily.com/releases/2011/08/110822124955.htm

    Really neat stuff! Thanks, Mike for you hard work!

    It's great to have a window on newly discovered dwarf planets and they seem to be just telling us more and more as time goes by.

    Thanks also for being a scientist who likes to communicate via blogs, public lectures, interviews, etc, with the general public, it really makes astronomy fun and fascinating for the astronomy loving or generally curious public.