The dwarf planet that gets no respect

Quick: name the three largest known objects in the Kuiper belt. If you’ve been paying close attention you will instantly get Eris and Pluto, and, if pressed, you will admit that no one knows which one is bigger. And the third? An unscientific poll of people who should know the answer (my daughter, my wife, my nephew) reveals that not a single one does.

The answer, of course, is Makemake (you remember how to pronounce this, right? Mah-kay-mah-kay, Polynesian style).  Makemake was discovered just months after the discoveries of Eris and of Haumea, and all were announced within days of each other. Eris and Haumea had important stories immediately attached to them (Eris was as big as Pluto! Haumea had suspicious discovery circumstances!), so poor Makemake stayed in the shadow of its more famous contemporaries. It was so overlooked that, in the hastily called press conference in which we announced the discoveries, I couldn’t even remember the official designation of Makemake when asked (it was 2005 FY9, of course; how could I have forgotten that?).

Comets!

Sometimes I like to write about things in the sky that I've been studying. Sometimes I like to write about scientific discoveries in the outer solar system. Sometimes I even write about wild speculations I have about the solar system. But, every once in a while, I get to just sit back and watch the sky go by.

I love comets. When I first started graduate school to get my Ph.D. in astronomy, I wanted to study the most distant galaxies in the world. But my Ph.D. advisor really wanted me to start by doing a project studying a comet (actually, he wanted all  of his graduate students to start with comets, because no one stuck with them; they jumped to galaxies as fast as they could). I fell in love with comets. Mostly, I think, I fell in love with the fact that you could use huge telescope to study things in the sky that you could actually see with your eyes or with binocular or with a camera. Things that were real. 

So I was pretty excited  about the prospect of Comet Panstarrs close to the tiny tiny crescent moon tonight. We have a great western horizon from my house and I was pretty sure we would have good views. Scientifically, I have nothing at stake. I'm not involved in any attempts to look at the comet with telescopes big or small, on the ground or in space. I just wanted to see it.

So I waited.

The tiny crescent moon was going to be easier to see, so up and down, back and forth, with binoculars I searched. THERE! It was, 25 minutes after sunset, higher than I thought. This was good news. It would be a good ~30 minutes before the comet set. Long enough that even my daughter Lilah would be able to see it.

(Lilah uses a placemat every day that has astronomy pictures [including, yes, Planet Pluto. It was a present. Really] on it, including comets. She is really really excited about seeing one in real life).

I had set out the camera and tripod earlier, and started taking long exposures, hoping to capture the comet. I kept seeing something. Maybe. To the left. Where I knew it should. Be. But? Well? I dunno.

Until, finally, jackpot:

See it? Barely? Something like 6 lunar diameters to the left of the moon?

And, I should mention, that I spend much less time than I should staring at the thin thin thin crecent moon with binoculars. It was spectacular. And it is monthly. Missed it tonight? Go next month.

The moon and comet slowly set in the west, while the sky got darker. Here, now, are a series of pictures where I just got to be a sky tourist. No big telescopes, no data collection, just me, a telephoto, a camera, my family [yes! Diane and Lilah both saw it! They were both a little shocked that they could actually see a comet!]. Here we go.

I love the view out my backyard. Particularly tonight.

It got lower and lower (and in the traffic pattern of LAX)

I love the palm trees on the horizon. Yup. I live in LA.

Finally it set.

I'll try again all this week from Hawaii, where I will be for the 20th anniversary of the opening of the Keck Observatory. It will seem a little more like science, though. There is something magical about looking from your backyard and seeing a visitor from far far far far beyond the Kuiper belt. And a spectacular moon.

The last shot I got, before I had to take Lilah in, read her a bed time story, and pack for Hawaii, looks like this:

There's a lot of murk between us and the moon, and us and the comet. But, really, it's just another night here in LA, as the sky darkens, the stars come out, and the world bustles underneath.

Sea salt (part 3)

[You should probably start with Part 1]

The first thing that you notice when you look at a spectrum of Europa -- from the Earth, from a spacecraft, it doesn’t really matter – is the ice. Ice is everywhere. The spectrum of ice is a very distinctive looking thing, with a quickly recognizable pattern of regions where the sunlight reflects strongly from the surface and regions where there is less reflectance (and remember the regions here means spectral regions, which means, essentially, we stare at one small spot on the surface, put the light through a prism to spread it all out, and see which colors of the rainbow are present and which are absent. In our case our rainbow is in infrared light that your eye can’t see, but the idea is still the same).

Sea Salt (part 2)

[don’t miss part 1] 

One of the biggest problems with trying to figure out what is on the surface of Europa was that the spectrograph on the Galileo spacecraft didn’t have a very fine view of the reflected light coming off the surface. The analogy I used in Part 1 was that Galileo was looking at fingerprints where you could only discern the rough pattern and not the individual ridges. You couldn’t use those fingerprints to know for sure who had smudged your crystal, though you might be able to rule out some people and you might become more suspicious of others.

There are two main reasons that the views from Galileo were not as fine as we would like. First Galileo was old when it arrived at Jupiter. Serious work began on the spacecraft in 1977, and with typical delays and atypical space shuttle accidents, it was finally launched, via a space shuttle, in 1989. Even the trip to Jupiter took longer than initially planned -- the shuttle accident spawned new rules which required the use of a less powerful rocket to launch Galileo from the orbiting shuttle -- so Galileo could not go directly to Jupiter but instead had to get gravity sligshots off of Venus and Earth before finally heading towards Jupiter and arriving in 1995, nearly twenty years after construction began. It was old on the first day it took data at Jupiter. (It was intentionally crashed into Jupiter in 2002 to prevent, among other things, an accidental crash into Europa, which would clearly disturb the whales).  Not surprisingly, the old technology was not as good as current technology in seeing precise spectral fingerprints.

Sea Salt (part 1)

Ever wonder what it would taste like if you could lick the icy surface of Jupiter’s Europa? The answer may be that it would taste a lot like that last mouthful of water that you accidentally drank when you were swimming at the beach on your last vacation. Just don’t take too long of a taste. At nearly 300 degrees (F) below zero your tongue will stick fast.

The composition of the surface of Europa has been hotly debated since the Galileo mission attempted to make detailed measurements more than a decade ago. Galileo’s tool for measuring the composition was spectroscopy – looking at the sunlight that reflects off of the surface of Europa and seeing which molecules leave characteristic fingerprints in that reflected sunlight. It’s a powerful technique, one that led to the initial discovery of water ice on the Galilean satellite, the discovery of frozen methane on distant bodies like Eris and Pluto and Makemake, and is even used on the Earth to map out mineral deposits for potential exploitation.

There is a Season 5

Some years back, when I first started writing this blog, I went strong for a year, and then felt a need for a rest. I was writing a book, doing science, raising an infant, all things that took time. So I declared that that was the end of Season 1. After a hiatus I was back. As I remember it, Season 2 was written mostly on weekend afternoons during the times that Lilah napped. But naps don’t last forever, and Season 2 ended when those naps did. As my book was just coming out I took a sabbatical from academic work  -- thus the start of Season 3 -- and wrote more, travelled around more, gave more talks, and became generally exhausted. I was thrilled when my sabbatical was over and I could return to science. There was a brief foray into Season 4 more than a year ago, but my heart wasn’t in it. And Lilah definitely no longer napped.

But, out of no where, there is a Season 5.

What’s changed?

And the answer is....

Almost a year ago, Eris – the, uh, most massive known dwarf planet -- passed directly in front of an otherwise anonymous star, momentarily causing the star to disappear, as seen from the earth. By carefully measuring the length of time that the star disappeared, astronomers made a very precise measurement of the size of Eris. I care about the size of Eris for many different reasons, but the most trivial yet emotional for me is the fact that, 5 years ago, I measured the size of Eris myself. We used a much more difficult and less accurate technique than watching a star disappear and timing it. We looked at Eris with the Hubble Space Telescope and carefully compared the tiny disk that we saw with a picture of a star (which should show no disk at all) and we claimed that we could tell that Eris had a diameter of about 1.3 pixels on the HST camera. Only 1.3 pixels! It’s hard to imagine that you could tell the difference between something 1.3 pixels across and 1.2 pixels. In fact, it had never been done before. Even we were not convinced at first that our technique was as accurate as it appeared to be. So we spent months on a careful analysis to make sure we had done nothing wrong. In the end our measurement technique passed every test we could dream up for it, and we became convinced that it was correct. We wrote the paper to announce it to the world. The diameter of Eris, we claimed, was 2400 km with an uncertainty of 100 km in either direction (I’ll be writing this as 2400±100 km).

This post might not be wrong

I have a new scientific paper coming out in the Astrophysical Journal that I am quite proud of having written. Even better, there is a chance that it might not even be wrong.

Back in something like seventh grade, I learned how science works. Scientists formulate a hypothesis and then they do experiments, and if enough experiments support the hypothesis, eventually the hypothesis becomes a theory. Right? Only, in my twenty-something years of actually doing science, things have rarely worked that way. Usually the process is more like this: do observations; discover something; develop explanation; repeat. This new paper, though, is a real live old fashioned hypothesis. It even has the word in the title: A hypothesis for the color diversity of the Kuiper belt.

The death of the 10th planet

A remembrance of 5 years ago, today, excerpted from How I Killed Pluto and Why It Had It Coming

As an astronomer, I have long had a professional aversion to waking up before dawn, preferring instead to see sunrises not as an early morning treat, but as the signal that the end of a long night of work has come, and it is finally time for overdue sleep. But in the pre-dawn of August 25^th, 2005, I awoke early and was up sneaking out the door, trying not to wake my wife Diane or our one-year-old daughter Lilah. I wasn’t quite quiet enough. As I was closing the front door behind me, Diane called out, “Good luck sweetie!”

I made the short drive downhill through the dark empty streets of Pasadena to the Caltech campus, where I found myself at 4:30 AM, freshly showered, partially awake, and uncharacteristically nicely dressed, unlocking my office building to let in news crews that had been waiting outside. All of the local news affiliates were there, as well as representatives of most of the national networks. Outside, a Japanese-speaking crew was pointing their TV camera up at the sky, their flood lamps disappearing into space. A glance at their TV monitors showed nothing but flood lamps disappearing into space.

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?