Mike Brown's Planets: Haumea

Showing posts with label Haumea. Show all posts

Free the dwarf planets!

Most people will probably think of tomorrow as the 5 year anniversary of the demotion of former-planet Pluto. That seems fair; the Pluto demotion got all of the news, caused all of the fights, and promoted all of the discussion. But now that tempers have cooled and the world has come to terms with a new more scientific eight-planet solar system, it is time to remember the other important thing that happened on that day five years ago. On August 24^th 2006 the International Astronomical Union (IAU) defined a new class of objects in the solar system: the dwarf planets.

As you will recall, the IAU declared that planets are the objects which go around the sun and gravitationally dominate their orbits. In our solar system, the eight planets are unique in that behavior. But there are other much smaller bodies out there – Pluto being the most famous – that look like planets (simply meaning that they are round) but are not dominant. Pluto and many of these other objects all circle the sun in similar orbits in what is called the Kuiper belt. These objects are the dwarf planets.

At the time this new class of dwarf planets was proposed, the IAU also declared that three dwarf planets were then known: Ceres (the largest asteroid), Eris (the newly discovered largest Kuiper belt object which precipitated all of this mess), and Pluto. In the entire five years since then, the IAU has declared two other objects to be dwarf planets: Makemake and Haumea.

A reasonable person might think that this means that there are five known objects in the solar system which fit the IAU definition of dwarf planet, but this reasonable person would be nowhere close to correct. By my best estimate there are possibly 390 known dwarf planets in the solar system (don’t worry, I’ll explain below).

What is going on here?

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The redemption of Snow White (Part 1)

Nearly four years ago, during the Ph.D. thesis research of my former graduate student Meg Schwamb, we discovered a distant bright Kuiper belt object. Our hope had been that something so distant would be like Sedna – far away, but part of an even more distant population. But it wasn’t. The object was more like Eris – far away, but on its way back in. The object got an official license plate number, based on the date of discovery: 2007 OR10.

Back then, I was surprised to have found something so bright so far away. It’s true that Eris is even brighter, but partially it is so bright because it is covered in icy frost that reflects almost all of its sunlight. 2007 OR10 didn’t seem big enough to have enough of a gravitational pull to hold onto enough gasses to have a frosty surface. So why should it be so bright?

I had a theory.

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Heading South, Looking Up

For most of the past decade the last thing I would do before going to bed was to step out on to my back patio and stare up at the sky for a few minutes, checking for clouds. If the skies were clear I always slept better. In the morning, I would hop out of bed and do the same thing, to see if any unexpected weather front had passed or cirrus had snuck in while I had been sleeping. If all was well with the skies, I knew that my robotic telescope 95 miles southeast of me, likely had a successful night scanning the skies, and I was excited to get up and get to my office to see the results. I knew that any clear night we might (and eventually did!) discover something larger than anything else ever seen past Neptune. It was just a matter of time and of keeping those pesky clouds away.

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Changing my world

After writing last week about a pretty major 5 year anniversary – the discovery on Dec 28^th 2004 of what is now called Haumea – it seems funny to be writing once again about a 5 year anniversary. But that’s just the way that reality worked. Eight days after discovering Haumea, and just a few days into the new year of 2005, I was back in my office again. I wanted to be studying Haumea – or Santa, as we called it then – since I was certain that it had to be bigger than Pluto, but, sadly for me, we still didn’t have any new data on it. We only had those first three pictures and there was nothing new to learn. We were scheduled to get more data soon, but not soon enough for sooth my anxiousness. My fingernails were nubs.

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A ghost of Christmas past

Five years ago I was sitting at work in that quiet week between Christmas and New Year’s Day desperately looking for the 10^th planet. I had made a bet five years before that that I would find a new planet by Dec 31, 2004. Time was running out. I was about to lose. I hate losing. So I was searching and researching all of the pictures of the sky I had taken over the past two years hoping that maybe somewhere in those old pictures was something that I had missed. Maybe there was still a planet to be found after all. Maybe I wasn’t going to lose my bet.

Just 3 days after Christmas I came the closest I had ever come. There was something in the old images that had been missed the first time around, and it was bright. I sent email to Chad Trujillo and David Rabinowitz, the two other astronomers I worked with, saying that this new object was so bright that it might well be twice the size of Pluto. Or bigger! Being right after Christmas, we of course called the object Santa.

Santa, which now goes by the official name of Haumea, we now know to be only about ½ the size of Pluto, and we call it – and Pluto – a dwarf planet rather than a planet. But back in those last days of 2004 when the discovery was first made, we had no idea where all of it was heading.

Our understanding of the Kuiper belt has changed dramatically in these past five years. The best example of this change comes, I think, from the discovery of a large Kuiper belt object that was announced just a few days ago. For me it was a particularly surprising discovery. For the first time I was not at the receiving end of a telescope making the discovery, I was at the receiving end of an email asking me about this new object called 2009 YE7.

“Never heard of it,” I thought.

But, by decoding the numbers, I could tell it was something that had just been discovered a few days before. Like anyone else, my first attempt to know more was a quick trip to Google.

Ah ha! A new large Kuiper belt object found from a telescope Chile, by David Rabinowitz! Yes, the same David Rabinowitz from the Haumea discovery. He has moved on to Chile to try to make newer discoveries from there, discoveries in parts of the sky that we didn’t look at back when we were working at Palomar Observatory outside of San Diego.

Based on preliminary information, it looked likely the 9^th largest Kuiper belt object ever found. David was clearly on to something good here.

I didn’t have time to delve into any more details because all of this had occurred as I was sitting in a movie theater waiting for the start of The Princess and the Frog with Lilah. She loved the part before the movie started because she could watch the on-screen ads. I checked my email and found out that there was a large Kuiper belt object that someone else had discovered. Then the movie started. I was itching to get more information about 2009 YE7, but I allowed my mind to drift down the bayou instead.

After the movie, though, my mind set to work on the implications of this new discovery. Based on its brightness it might well be a perfect size to test one of my new theories about medium-sized Kuiper belt objects. I feel like I now understand the largest objects, and I fear that I will never understand the smallest objects, but the middle ones are within grasp, if we can just find a few more to test some pet theories about them. For 2009 YE7 to be a good candidate for my theory we need to know if it has a moon, what color it is, and what materials are on its surface. Then we’ll see. I started thinking about where 2009 YE7 is in the sky, what telescopes I could use to point at it, how to time the observations.

Even as I was thinking these thoughts, my mind was drifting back to the discovery of Haumea exactly five years earlier. Back then, on the day of the discovery, we knew absolutely nothing. I had no good ideas about what Haumea would be like; I had no theories I was testing, no hypothesis to work out, no predictions to boldly claim. We were simply in the very early stages of exploration to see what was there. The exploration was going well! Soon after the discovery of Haumea, we tripled the jackpot by first discovering Eris – the one we now know to be larger than Pluto – just two weeks later, and then Makemake – the one we now know to be just a bit smaller than Pluto – a few months later. I felt the universe was exploding with new bright Kuiper belt objects and possibilities were endless. We didn’t know anything about what these objects were, how big they were, what they were made of, or what had happened to them. In April 2005 I still believed it possible that they were all 3 larger than Pluto and that they would eventually be called the 10^th, 11^th, and 12^th planets.

In the five years since, we’ve learned a tremendous amount. We determined their sizes and gave up on any of the things in the Kuiper belt being planets (I lost my bet, too). We found Haumea’s two moons; we found that it had a surface that looks like an almost perfect glaze of ice; we found that it was white, again like ice, we found it elongated and spinning end over end every 4 hours, and we found a cloud of other smaller objects on similar orbits. We found that Makemake is covered in thick layers of frozen methane, that Eris is bigger and heavier than Pluto, and, most importantly, that things were beginning to make sense. We had moved from exploration to explanation. Haumea’s strange properties – and that cloud of objects in similar orbits – were all a consequence of a giant impact 4 billion years ago or so. Eris and Makemake were large enough that they should have methane on them.

With our new found knowledge even things that had been discovered earlier were finally being put in context. Quaoar is a weird combination of Haumea and Makemake. Orcus is what Makemake would look like if it were just a little smaller. Varuna is, well, Varuna is still confusing.

Mostly, though, now instead of each object being an individually mystery to be solved, each new object is a piece of a puzzle where many of the pieces have already been put into place. With only a little information, we can guess where the piece likely goes.

Which brings me back to 2009 YE7. Five years ago, its discovery would have been a thorough mystery to solve. But when I first heard of it two days ago, it was, instead, potentially the exact area of the puzzle I had been looking to fill in. I thought it was going to be that perfect medium-sized Kuiper belt object to try out my theories. I just needed some telescopes, some computers, and some time, and everything would fall into place. I thought it would be a fun month or two to try to collect and analyze the data quickly.

I was wrong. It took me about 2 minutes to figure out almost everything that there is to know about this object and its violent history.

When I finally got home and got a chance to look a little more closely (and “a little more closely” here doesn’t mean much; as of today still nothing is known about the object except for its position for about the past two weeks), I realized two things that told the whole story. First, 2009 is YE7 bright. In absolute terms, it is the 9^th brightest object, which is what led to the reasonable assumption that it is likely the 9^th largest object (by absolute brightness here, I mean the brightness things would have if they were all the same distance away; some objects are bright just by virtue of being close). Second, the orbit of 2009 YE7 is tilted relative to the planets by 29 degrees. Following the position of an object for only 2 weeks doesn’t give you a precise measurement of much about its orbit, but that tilt is one thing that is solidly known even with this limited data. An angle of 29 degrees is an unusually high angle. Not too many objects are tilted by that much. But one that is is Haumea. Ah! Haumea! Haumea with its family of shards all going around the sun on orbits just like it. Tilted by 29 degrees.

2009 YE7, the brightest object discovered in the Kuiper belt in almost 5 years, is almost certainly one of the large shards (perhaps even the largest) blasted off of the surface of Haumea 4 billion years ago. 2009 YE7 and the other shards have been circling the sun on their own ever since. It is bright not because it is particularly large, but because all of the fragments of Haumea have extremely bright, reflective, icy surfaces which make them stand out against the more common darker Kuiper belt objects. 2009 YE7 is not the 9^th largest Kuiper belt object; it is probably about 440 km in diameter and so in the top 50.

I will admit that I miss the old Kuiper belt. I miss the mystery and wonder of exploration of unknown territories. There will be nothing like it in solar system studies for a long time to come, I suspect. Perhaps ever. And yet, as much as exploration is thrilling and exhilarating, there is something deeply satisfying about learning about a new bright Kuiper belt object while sitting in a movie with your daughter and understanding most of its 4.5 billion year history soon after getting home. We’ve learned so much. We’ve come so far.

….

A technical aside on 2009 YE7. The tilt of the orbit alone does not prove it to be a Haumea fragment, particularly since the other parameters of the orbit are still poorly known. Above, when I say it is “almost certainly” a fragment, the assessment is a judgment based on experience, rather than a scientific fact. But I’m pretty confident, sufficiently confident that I’d be willing to bet (I need to win back some of my loss from that old 2005 bet, right?). The real confirmation, though, would come from an infrared spectrum that shows evidence of deep water ice absorption features, but that requires a pretty big telescope. Almost as good, though, would be optical colors showing it to be white (solar-colored, really) like all of the other Haumea fragments. Measuring these colors is actually quite easy; all you need is a ~1 meter telescope and ~1 night of observing. Any two photometric bands would be good. I would probably just try V and R. Then measure a solar colored standard star and compare. They will be the same, I predict. Go do it! Tell me the answer! It’s fun to make predictions, and even more fun for them to come true.

…….

I don’t actually think the exploration is finished yet. The southern skies are still largely terra incognito for the Kuiper belt. David Rabinowitz has clearly just started the journey; others are scanning out there, too. Much of what they find may indeed fit into the frame of the puzzle that we already know, but I still hope some day to open up some email and read about some new discovery and sit stunned realizing that someone just found something that I didn’t expect at all.

Homeward bound

I’m on my way home today from a quick trip a third of the way around the world to use a telescope.

Astronomers are, of necessity, vagabonds. Sometimes the thing that you want to look at in the sky is only viewable from the southern hemisphere, so down to Chile you go. Sometimes the thing is so faint that only the biggest telescopes around are worthwhile, so it’s off to Hawaii. What’s rare, though, is to spend 24 hours flying from Los Angeles all the way to the Canary Islands – a group of high volcanic crags off the coast of Africa with a latitude almost identical to that of southern California – to use a telescope smaller than the one that is just a three hour drive from my house.

When, after a day of travel, I got to La Palma, the island whose highest peak is strewn with telescopes, and I stepped outside into the dark dark night sky, I was greeted with exactly the same sky that I see in Los Angeles. OK, there were many many more stars, but they were all in their right places, and nothing was there that I couldn’t have seen from home.

So why spend all of that time to travel to a telescope smaller than my local one when all of the same sights were visible? Because when it was night time in the Canary Islands the sun was still high overhead in southern California. And the thing I was hoping to see only happened right then. If I had stayed home and waited eight hours to look later I would have seen nothing.

Here is what I hoped to see: that night the funny oblong fast spinning dwarf planet Haumea was passing directly in front of one of its satellites (Namaka is its name). If I could determine precisely when it happened and how long it lasted I could learn many things about Haumea (its size and crazy shape, maybe also its interior structure) and also about Namaka (how big it is, how much it is being tugged around by the other satellite, Hi’iaka). But all of this was happening so far away that the only way I could tell when Namaka disappeared behind Haumea was that the total amount of light coming from Haumea should dip by about 1%, So at the telescope I spent two entire nights doing nothing but staring at Haumea and measuring precisely how bright it was every two minutes. For comparison, I also checked a couple of stars nearby at the same time. If they stayed steady while Haumea dipped in brightness I would know I was in business.

It all sounds so simple.

In reality, though, stars never stay the same all night long. They get brighter as they get higher in the sky and fainter as they drop. Even on the clearest nights they fluctuate due to changing atmospheric conditions. Seeing this tiny drop in brightness of Haumea in the face of all of this intrinsic variability is a tough task.

But I tried.

After two nights at the telescope I am leaving with my laptop filled with pictures of the sky and my hopes high. Did we see it? Did we detect this tiny dip which told us that Namaka disappeared? I think so. I have a plane ride from London to Los Angeles tomorrow to look at the data more closely and convince myself what might or might not be there. But I think so.

If we didn’t detect anything it’s bad news. Perhaps our predictions are off, or it’s just too small of a blip for us to ever really see. But if we did detect it then our work is really just begun. Turning that little blip in the sky into concrete information about Haumea and Namaka will take a lot longer than tomorrow’s plane ride. There will be many more such trips around the world to be in precisely the right place when it happens again. There will be detailed computer models of the exact time and depth and duration of the blips. There will be confusion and ambiguity. But that is all in the future. For now I have the simple pleasure of long uninterrupted plane ride where I can stare and poke at the data, catch up on some reading, and think about these dwarf planets. And at the end I get to pick up my daughter from school and she’ll ask “Daddy daddy daddy did you see any stars?” and I’ll tell her that I did, but that the stars here at home are always the very best ones in the sky.

Baby Pictures

Last night, for the second time this decade, I got to have dinner and give a talk on the floor of the dome of the famous 200-inch Hale telescope at Palomar Observatory. It’s rare for anyone to give a talk on the floor of the 200-inch telescope, because Palomar, like every other large telescope around the planet, is used night after night after night looking at everything from the nearest asteroids to the edge of the universe. Few or no pauses are allowed for frivolities such as dinners and talks (in this case we got in, had dinner, gave a talk, and vacated the floor just as the sun was setting). So it was a treat when I got invited to speak to an intimate gathering of supporters of Palomar and Caltech – the university where I work and the one which, not incidentally, owns and operates Palomar – on the floor of the dome. It was even more of a treat because I had been the speaker at the last one of these dinner 8 ½ years ago, and it was particularly interesting to reminisce about what had happened in the almost-decade since then.

When I gave that first talk, in September of 2000, I was a young assistant professor at Caltech who had embarked on what I think it is fair to say was an audacious project: I was going to go find the 10^th planet. I had spent the previous two years systematically scanning a wide swath of sky using the seemingly ancient technology of manually slapping giant glass photographic plates to the back of a wide-field telescope, exposing the photographic plates to the sky for half an hour at a time, developing the photographic plates in the darkroom downstairs, and then looking at repeat exposures of the same patch of the sky to see if – perhaps! – I could find something that had moved. It was exactly what Clyde Tombaugh had done 70 years earlier that had led to the discovery of Pluto, but, no, I had the advantage of a much larger telescope and the use of computers to help analyze the final photographic plates.

At the time of the talk 8 ½ years ago I was in the third year of the project, where I was going back with a larger telescope to try to confirm anything that I thought I had detected during the first two years with the photographic survey. I told my audience sitting under the 200-inch telescope about what I was doing and about what I hoped to find. I told them about photographic technology versus the new digital cameras now widely in use. I told them about why I thought that after this third year I was going to have made that discovery I was hoping for and the 10^th planet would be in our grasp. It was, I daresay, a talk full of exciting promise.

It’s a good thing I wasn’t asked to give a follow up talk right away.

By the following year it was clear that my three year survey had found a grand total of absolutely nothing.

I told that story last night at the 200-inch telescope and everyone chuckled. They chuckled, of course, only because they knew what came in the years that followed. What came next? We scraped the photographic plates, installed experimental digital cameras, roboticized the telescope, and kept scanning and scanning and scanning. With the benefit of the faster and more sensitive digital cameras we slowly surveyed the whole northern sky and blew the outer solar system open.

Last night I showed my baby pictures from the past decade. I showed Quaoar, the first large Kuiper belt object that we found, the one named for the creation force of the local Tongva Native American tribe, the harbinger of larger objects to come. I showed Orcus with its newly named moon Vanth, and talked about its odd mirror-image orbit to Pluto. I showed Sedna, far beyond the Kuiper belt, in an orbit that takes 12,000 years to go around the sun, named for the frigid Inuit goddess of the sea, a beacon pulling us even further in the distant solar system. I showed Haumea, with her two moons Hi’iiaka and Namaka, spinning her was across the sky, I showed lonely Makemake, bird god of the Rapa Nui, the runt of the litter that produced the Big Three of Makemake, Pluto, and Eris. And then, of course, I showed Eris her, in all of her discord and strife, with her tiny moon Dysnomia circling her.

I really do feel like each one of these is like a child to me. And, like children, whenever the rest of them are not in the room, I will secretly tell you that this one is my favorite. They’re all my favorites. I can tell you stories about their little quirks, their odd habits, and a funny thing that this one did the other day when it thought no one was watching (did you know that the night before Namaka went right behind Haumea playing a little hide-and-seek with us? Silly little moon.).

Something else was particularly interesting to me about my talk 8 ½ years ago at Palomar. Something happened that day that I am certain I will never forget. I was inside the telescope waiting for the group of Caltech supporters to arrive, and finally hearing the knock on the outside door, I opened the door, and, as my eyes adjusted to the blinding outside light, I was greeted by the director of the group of Caltech supporters. She had worked on the Caltech campus for years, but somehow our paths had never crossed. I had certainly never seen her before. How do I know for sure -- you might ask. Trust me -- is my answer. I would have remembered. She walked in the door, and I fumbled my words introducing myself. Her name was Diane Binney.

Diane Binney doesn’t work at Caltech anymore, but she came on the trip to Palomar last night anyway. It was her first time back to the mountain since that time 8 ½ years ago when I gave a talk up there. She came to see old friends and revisit old places. And, since she hadn’t seen many of the people in a long time, she brought baby pictures of her own. She has a 3 ½ year old daughter named Lilah. Lilah has Diane’s last name as a middle name, but she gets the last name from her father. Me. Lilah Binney Brown.

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 7^th 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.

Haumea

On December 28^th, 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 1^st, 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 7^th 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 10^th 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.

Officially:

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.

Circular arguments

When something exciting was happening and astronomers wanted other astronomers around the world to know, they used to send a telegram to one central location from which subsequent telegrams were then exploded to observatories around the world. The CBAT --Central Bureau for Astronomical Telegrams -- still exists today to provide the same service, except that it is all done by email today. The CBAT issues International Astronomical Union Circulars, which used to be, in fact, rectangular, approximately the size of an index card, on which new exciting information was mailed. Again, today, it is all email. The switch from telegrams arriving at observatories to emails arriving in everyones already overstuffed in box is another sign of the quaintness being snuffed out of astronomy in favor of efficiency. And I, for one, say thank goodness for efficiency.

Today, we are issuing our IAU Circular describing the moon shadows. It will read something like this:

Mutual Events of 2003 EL 61 and its Inner Satellite

Daniel Fabrycky (Harvard University), Darin Ragozzine & Michael Brown (California Institute of Technology) and Matthew Holman (Smithsonian Astrophysical Observatory)

Orbital fits to the relative astrometric positions of dwarf planet 2003 EL61 (IAUC 8577) and its inner satellite, S/2005 (2003 EL_61) 2 (IAUC 8636), have revealed a near edge-on orbit, implying likely mutual events. The orbital model was based on images from HST (WFPC2) and Keck (LGS-AO). Due to the changing orientation of the Earth-EL_61 line of sight, the orbit is moving closer to edge-on until August 2008, after which the orbit will open up again. The current distance of closest projected approach is ~500 km, nearly the same as the semi-minor axis of the triaxial primary (Rabinowitz et al. 2005, ApJ, 639, 1238), so events will likely be grazing. Shadows of the satellite and EL_61 will likely miss each other. The unocculted lightcurve has double-peaked rotational modulation of full amplitude 0.25 mag and period 3.9 hours; template lightcurves of this variation are available from Holman. The duration of the events will be between 0 and ~6 hours; ingress and egress will consist of ~0.03 magnitude changes on a timescale of ~10 minutes. Telescopes distributed in longitude are needed to follow events as the orbital period is 18.36 d. The main body is rather faint (V~17.4 mag), so high-precision photometry requires moderate (~1 m) collecting area.

Due to orbital eccentricity, events in which the main body occults the satellite are more likely to occur than events in which the satellite occults the main body. Our orbital model predicts mid-event times as follows (add or subtract up to 3 hours for ingress or egress times).

For the satellite occulting the main body:

HJD 2454617.58 +/- 0.07 = 5/31 01:50+/-1:40 UT

HJD 2454635.84 +/- 0.07

HJD 2454654.11 +/- 0.07

HJD 2454672.48 +/- 0.08

For the main body occulting the satellite:

HJD 2454625.22 +/- 0.07 = 6/07 17:10+/-1:40 UT

HJD 2454643.45 +/- 0.07

HJD 2454661.79 +/- 0.1

-------

What does all of this mean? First, a little sadness. We missed most of the shadows by a few years. There is only a chance to observe about 3 more this year, and then not again for 130 years.

The next event is visible over Asian/Europe, but we think it is likely to just be a graze, so nothing will be clear. After that we are on to Hawaii and Japan again for June 7th.

Honestly, I think we're too late. But what a great project it will be for our great-great-great-grandkids.

Moon shadow Monday

On Friday morning, my graduate student, Darin Ragozzine, sent email around to the whole group with the subject "Can I borrow the Keck telescope on Monday night?"
On Thursday night Darin had gotten the third of five pictures from the Hubble Space Telescope of 2003 EL61, aka Santa, and its two moons (rudolph and blitzen). With this third picture Darin could final put together the orbit and Blitzen to see if, as we hoped, Blitzen is currently passing directly in front of and behind Santa. And it is!
Here's what we now known. Blitzen takes about 18 days to go around Santa, so once every 9 days it either passes directly in front or behind. Measuring the precise times of these events would lead us to an exquisite knowledge about Santa and its moons.
But there is bad news, too. This series of events doesn't last forever. As Santa orbits the sun our viewing angle changes, and an orbit that is currently edge on opens up so there are no more events. As far as we can currently tell, these events will only be observable for a little more than a month, and then not again for 130 years. We have about five events left in our lifetimes.
Yikes!
The first one occurs this Monday night/Tuesday morning, and it is only observable for eastern Asia and Hawaii. Hawaii! At this point Darin wisely remembered that on Monday night another member of our group -- Emily Schaller (that is Dr. Emily after her successful Ph.D. thesis defense 2 weeks ago) -- is already scheduled to be at the Keck telescope (the biggest telescope in the world) on Monday night. We'll be looking from there!
The fact that Emily is at Keck that night is just good luck; we were scheduled 6 months ago to do something else entirely. At a telescope like Keck once you're on the schedule the night is yours to do what you want. It had just better be good. This will definitely be good.
Unfortunately the event starts a little late in the night. By the time Blizten goes behind Santa it will already be nearing morning in Hawaii. By the time Blitzen reemerges the sun will be up. Emily will miss it.
Late Friday afternoon I pulled out a map of the earth and drew a huge circle around the places where it will be dark when Santa reemerges. India. Japan. China. Korea. Far eastern Russia. I then got my list of world wide observatories to see what was there. The largest telescope and best chance is in India. Other good ones are in Japan and Taiwan.
How do you get someone half a world away to try to observe something like this in two days? I don't know anyone at any of these observatories. I resorted to google searching to find any email addresses I could for each place and blindly sending email out. Next, I thought: who do I know that might know someone? I contaced an Indian astronomer at Caltech. I then suddenly remembered that one of my own graduate students, Meg Schwamb, worked for a while at an observatory in Taiwan. She had some good thoughts about who to contact, and she started emailing.
By the end of the night last night we had emailed dozens of people across eastern Asia. We're waiting to see who, if anyone, will respond.
Assuming all goes well and we can confirm this event Monday night, we will publicly announce the next one that happens about 9 days later so we can get everyone possible involved. Based on our current data, we think the next one occurs over Europe and the eastern United States. Stay tuned.
In the meantime, here is the pleading email that I sent halfway around the world last night:
>Dear Colleagues:
>We have just determined that one of the satellites of 2003 EL61, the 4th
>largest known Kuiper belt object, is currently in a perfectly edge-on
>orbit and is undergoing mutual eclipses and occultations for the next
>few months. After this year it appears the next such events will not
>occur for the next 130 years.
>
>Study of these events yields an incredible bonanza of scientific results
>(part of a popular article describing results from the recnt
>Pluto-Charon mutual events can be read at
>http://books.google.com/books?id=G7UtYkLQoYoC&pg=PA545&lpg=PA545&dq=mutual+event+pluto&source=web&ots=jDOfb3sWHL&sig=jjLkVTF21FuL-8TiGUT0gy7X5nQ&hl=en
>
>These events give similar exquisite geometric constraints as transits of
>extra-solar planets.
>
>We just found out that mutual events are currently occurring, and it
>appears that only 5 more events will occur this century. The next one is
>this Tuesday night at ~16:00 UT. This event can only be observed from
>~India, China, Taiwan, Japan. We are currently trying to enlist as many
>observatories as possible to obtain several hours of photometry of this
>event. Currently the uncertainty in the timing is a few hours, but over
>the weekend we will get one more astrometric point from HST which should
>allow us to predict the time to about ± 1 hour.
>
>2003 EL61 is approximately 17th magnitude. The occulatation will
>diminish the total brightness by approximately 1%. We thus think that
>only ~1-meter telescopes or larger will have a chance of being able to
>obtain an accurate time for the event. The diminishing will occur over
>~20 minutes. 2003 El61 varies in magnitude by ~.2 mags over a 2 hour
>period, so it will also be important to obtain photometry during the
>same phase for comparison. We also have some extremely accurate HST
>photometry over the entire rotation period to which any ground-based
>photometry could be compared.
>
>We are attempting to alert all major observatories which might be able
>to observe this event in the hopes that each of these 5 events can be
>thoroughly studied. We are happy to coordinate analysis of these
>observations, but we are equally happy for people to perform their own
>analyses of these exciting events. If anyone does observe, however, we
>would greatly appreciate a report of either success or lack of success
>of observing the dimming due to the occultation. Any timing that can be
>provided provides a better prediction for the [small number of]
>remaining events.
>
>We apologize for the short notice; we were not anticipating that these
>events were occurring right now. Because of the short notice, I
>personally will not be available for the next 2 days to help coordinate
>(I am taking my geology class on a trip to the mountains where I have no
>email contact), but my student Megan Schwamb (mschwamb@caltech.edu) will
>be coordinating events in my absence and will be happy to answer any
>questions in my absence.
>
>Thank you for your consideration and I look forward to working with you,
>if possible, on these extremely exciting observations.
>
>Sincerely,
>
>Mike Brown
>
>
>
>
>
>

Nervous gyrations

On Sunday May 11^th, at 6:53 PM, looking from my backyard, the sun will still be appealingly gleaming above the western horizon, with almost an hour to go before it sets. Almost straight overhead the almost-first quarter moon will be waiting to steal the show as soon as the sun is gone. But I won’t be looking at either one. My eyes will be focused just above the eastern horizon where my current favorite outer solar system object – 2003 EL61, better known as Santa – will just be rising. OK, so I won’t see anything but blue sky; even at night Santa is about 10,000 times too faint to see with the naked eye. But I’ll be looking that direction thinking about the fact that at that moment the Hubble Space Telescope will be joining our hunt for moon shadows. On May 11^th and then four other days over the following two week period, the telescope will come around the earth, swing towards Santa, and snap a quartet of pictures to help us determine precisely where the small satellite (aka Blitzen) is.

This is good news! Without the Hubble we feared that it would be another year or two before we figured out the orbit well, and in that time it was quite possible that shadows of Blitzen would no longer be falling on Santa. The case that we made in our emergency plea to use the telescope must have been compelling; within two days of sending in the proposal we had heard back that we had been approved. But there was some bad news, too. Hubble is approaching two decades in space, so things sometimes fail. Visits by the space shuttle continually fix the Hubble back up and add new capabilities, but with the space shuttle fleet itself barely limping along, Hubble has gone without a visit now for more than six years (a new visit is scheduled for late summer). In that time some of its gyroscopes have failed.

Gyroscopes are critical on a spacecraft like the Hubble, because they keep track of which direction is which. They work just like a spinning top works. As long as the top stays spinning fast it stays pointed in the same direction (in the case of a top that would be up); as the spinning slows the top starts to wobble and finally falls down. In space, with no gravity, the top would just keep spinning in whichever direction it was originally pointed. If the spacecraft does some maneuver to point in a different direction, the top still stays fixed pointing in whatever direction it started. Tops – which is all that gyroscopes really are – are great for space, because, with no gravity and no compass, there are not many other ways to figure out which direction you’re pointing.

If the Hubble had no gyroscopes left it couldn’t do anything. Luckily, three still survive. With three gyroscopes you can point anywhere in space at anytime. Wisely, though, the people who run Hubble decided that it was better to keep one in reserve in case one of these last three fails. So Hubble operates with two gyros. With only two you can still point to anywhere in the sky, but not at anytime. And this where the bad news comes in. After about noon on May 24^th Hubble can’t observe Santa again for a few months.

The people at Hubble wanted to know: was it still worth doing the observations? We had to ponder. We think Blitzen takes about 19 days to go around Santa. From May 11^th (which was the soonest we could get on the telescope) until May 24^th is only 13 days. So we won’t see the complete orbit, but we think we’ll see enough to be able to calculate where Blitzen is the rest of the time. “Proceed!” we said.

But then there was worse news. Hubble uses the gyros for course pointing, but for keeping the telescope absolutely still during the course of the observations it also tracks a pair of bright stars close to the target. And, by bad luck, there aren’t enough of them close to Santa. A single star is available up until the 19^th, and then absolutely nothing. We can do the observations, slightly degraded, with a single guide star, but there is nothing to be done after the 19^th. So now we were crammed into May 11^th through the 19^th, an eight day window, when we really had hoped for a full nineteen day window. They asked again: is it still worth it?

By luck, if you only had eight days out of nineteen, these might be precisely the eight days you would want. They are when Blitzen is closest to Santa, which is the part of the orbit we need to know best. But still, it’s going to make our lives even harder than before. Will it still work? We did some quick calculations and decided, once again, we could do it. So we’re on for our eight days in May.

Now I’m nervous. We promised a pretty spectacular result to the people at Hubble. We need to deliver. There is always the chance that the new data will show that the shadows just finished happening and we’re too late. That would be bad luck, but we could at least hold our heads high and say we figured it out, just a little late. No, what makes me nervous is the possibility that we will get the data and still not be able to figure it out. People will say: OK, what’s the answer? And we will have to say. Well, um, we still can’t quite calculate the orbit. We can’t tell you when there will be moon shadows. Wait until next year.

I don’t think this will happen, so mostly it’s just paranoia. And I always have it. Every single evening when I am sitting at big telescope and the sun goes down and the dome shutters open I get similarly nervous. What if we did something wrong and all of our careful calculations about what we are going to look at and what we might discover were wrong? What if we forgot to take something into account? What if there is a better way to be using the telescope? What if…

And then the sky darkens and our first targets appear on the screen and I forget all of the nervousness and worry and get to work.

The same thing will happen, I hope, with this project. I won’t be at the telescope this time. I’ll be sitting at my desk sometime a few days after May 11^th, when the data finally get transmitted and processed and downloaded onto my computer, and I’ll pull up the first image and forget all of the nervousness and worry and get to work.

I'm trying to follow a moon shadow

I wrote a few weeks back about the orderly process of obtaining time on telescopes. Once or twice a year you write a proposal that explains exactly what you want to do with the telescope and why and what you hope to accomplish, and all of the proposals are read by another group of astronomers who pick the ones they think are the best, and they assign them to nights on the telescope. So controlled. So rational.

This annual or biannual cycle is about right for keeping up with new ideas and new discoveries and working on them to the point where you can write something coherent and convincing for a proposal. If proposals were accepted every month instead of every six months, you would have nothing new to write. If they were accepted once every 5 years, you would have new ideas in the interim that there were no ways to explore. I like the system.

But, every once in a while, something happens where you need to be at a telescope right now, and you didn’t realize it in time to have written a proposal six months or a year ago.

Such is the case for me at this very moment.

First, a little history. We discovered the Kuiper belt object 2003 EL61 (which has no real name, only this license plate number; I’ll explain why, and my irritation with the IAU for refusing to allow this object to get a name, in a later posting) back on Dec 28^th, 2004 (with the discovery so close to Christmas and no other name forthcoming, we generally refer to this object as Santa). Within about a month we had discovered that Santa had a moon around it (which we call Rudolph, of course). By mid-summer we had collected enough data to be able to calculate the precise orbit of Rudolph around Santa. We found that Rudolph goes around Santa every 49 days in a nearly circular orbit, and, interestingly, the orbit is currently almost edge on to us. Orbits can be edge on or face on or anywhere in between. Face on means that we are viewing the orbit from above, and we see the moon circling the object. Edge on means that we are viewing the orbit from the side and all we see is the moon going up and down in a line. In between we would go from the circle of face on, through a series of increasingly squashed ellipses, until finally we got to the straight line of edge on. When we looked exceedingly closely at Rudolph we realized that it wasn’t quite perfectly edge on, we could see a tiny little bit of the squashed ellipse.

By the fall of 2005 we realized that something else was going on, too. Santa and Rudolph had another companion. It had been in the data all along, but we hadn’t noticed it at first because it was so much closer and fainter than Rudolph that sometimes the data weren’t good enough to discern it. We call this one Blitzen. Because we couldn’t always see Blitzen we couldn’t actually calculate its orbit around Santa. Complicating matters even more, Blitzen is so close to Rudolph that the extra gravitational pull from Rudolph continuously changes Blitzen’s orbit. Figureing out Blitzen’s orbit was going to be very complicated.

Since then, we have continued to try to see where Blitzen is, but we still have a hard time. In 2006 we got some nice images of Blitzen with the Hubble Space Telescope, but not enough, because Rudolph had already changed the orbit from 2005. In 2007 we tried and tried and tried at the Gemini telescope with only a little success, and, this year, getting a picture of Blitzen was one of our main goals for the laser guide star adaptive optics Keck trip that happened last month. We still lack enough data to figure out the precise orbit, but from the most recent good picture that we got a few weeks back we suddenly realized that the orbit of Blitzen appears to be exactly edge on. We had always known it was close, but we never had good enough data to see precisely how close. Now we think we do.

An orbit that is edge on will not stay that way long. As Santa goes around the sun, our viewing angle of the orbit will change. If it is edge on now, it will slowly move to more face on before moving again to edge on in about 130 years.

While most of the time we don’t care exactly what orientation an orbit is to us, edge on is special. Edge on means that sometimes Blitzen travels directly in front of Santa, and sometimes directly behind. The shadow of Blitzen will at times traverse the face of Santa. All of these things give us the opportunity to learn things about Santa and about Blitzen that we have no other way of knowing. If we can see the shadow hit the face of Santa (by looking for a slight dimming in the overall light from Santa), we will know, much more precisely than any other way possible, where Blitzen is, the size of Santa and Blitzen, how bright Blitzen is, and many other things that we had only dreamed of knowing before. Edge on orbits are fantastic scientific boon!

Even though we think we now have enough data to know that the orbit is edge on, Rudolph still changes Blitzen’s orbit around enough that we still don’t have enough data to calculate the orbit well enough to know when the shadow will transit or when Blitzen will be eclipsed. For that we need more time at the telescope. Usually we would just wait until next year to write another proposal, but it is very likely that by next year the edge on orbit will have opened slightly, and the all of the shadows and eclipses and occultations that have been taking place unobserved will not occur again for 130 years.

What to do? The only sure-fire solution is to use the Hubble Space Telescope. While we could try telescopes here on the ground, the vagaries of weather and the variable quality of the data mean that there is still a pretty good chance that we wouldn’t know the orbit soon enough. The Hubble, however, sitting high above the earth, has no weather to contend with. We know exactly what we are going to get, and we know exactly how good it is going to be. We need Hubble!

But the proposals to use the Hubble were due a month ago. We have to wait 11 months for our next shot.

Luckily, people who run telescopes are smart enough to have foreseen things like this long ago. The Hubble has a special proposal you can write at any time, called a Director’s Discretionary proposal, which can turn the telescope to a new target at a moment’s notice (well, ok, at a week or two notice). Just the thing!

So this week has been emergency proposal week. In between teaching geology class, writing a paper, preparing for a scientific talk at JPL on Monday, and spending time with my family, I wrote an emergency Director’s Discretionary proposal. It is not the best proposal I’ve ever written, but I think it makes the case. We need to know the precise orbit of Blitzen now so we can figure out when shadows and transits and occultations occur. And when we figure all of this out we need to make the information public as quickly as possible so everyone with a big telescope has the opportunity to make measurements of these events. And without the Hubble Space Telescope we will know this all too late. Therefore please please (pretty please) let us use the telescope.

The proposal goes to the director today. The decision is made by next week. If accepted, the pictures would be taken in a few weeks, and we would know when the first events would be occurring within about a month. Got a big telescope with which you want to chase a moon shadow with me? Stay tuned.

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