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Lecture: Mike Brown, "How I Killed Pluto and Why It Had It Coming"

Last night, thanks to the Boston Skeptics organization, Nomi and I got to meet Mike Brown, the man who discovered Eris and indirectly led to the demotion of Pluto's status as a planet.

Nomi S. Burstein, Mike Brown, Michael A. Burstein Nomi S. Burstein, Mike Brown, Michael A. Burstein
Photo ©2011 D. Moskowitz. All rights reserved.

The Boston Skeptics had arranged for Mike Brown to give a talk last night at Tommy Doyle's in Cambridge. We had only found out about the talk on Tuesday morning, but thanks to a good friend who volunteered to put our kids to bed, we managed to clear our schedule to attend. But when the National Weather Service predicted a significant snowfall starting yesterday afternoon, we weren't sure if we were going to make it to the lecture.

The roads turned out to be clear, and we made it to the pub just as things were getting started at 7 pm. Brown was already there, and willing to sign books even before his talk began. We brought our copy of his book over to him and introduced ourselves. It turned out he had already heard of us and was as delighted to meet us as we were to meet him. He was very gracious and personable, and his talk demonstrated quite clearly why he had won a teaching award.

The space was somewhat small and crowded, and not designed very well for his talk, I'm afraid. The screen for his presentation slides didn't face the main body of the room, so it was hard for us to see. Having arrived just at 7 pm, Nomi and I had difficulty finding seating, but a nice scientist named Jason allowed us to sit at the table with him and his two friends.

Brown discussed his research in the outer solar system. He had a graphic that showed just how big in comparison all the planets are to each other and to the objects in the Kuiper Belt, making it clear why Pluto is such an outlier. He talked about the telescopes at Palomar Observatory that they use to photograph the sky, and how they look for those tiny objects that are so far away. Back when Clyde Tombaugh found Pluto, Tombaugh used a blink comparator, a device that allowed him to compare two photos of the same portion of sky from two different nights to see if any points of light had moved. Brown relied on something similar, except in his case a computer went through a slew of photos and would present him with likely candidates in his morning email. I wonder what Tombaugh would have thought of that.

Brown seemed very respectful of those of us who still feel that Pluto should be considered a planet. He understands where the impulse comes from, and in a way, if Pluto were still a planet it would be better for him. After all, he'd be able to go down in history as the discoverer of the tenth planet (and eleventh, and twelfth, and thirteenth, etc.) Instead, he's going to be the discoverer of a lot of astronomical bodies that he himself points out are rather insignificant to the solar system.

Although he feels that Pluto should not be a planet, it turns out we do have a few points of agreement. He and we both feel that the term "dwarf planet" is a bad one, and he also has issues with the way the term "planet" is currently being defined by the IAU.

Brown also spun a brief tale of alternate history that, as a science fiction writer, I found fascinating. He pointed out that the discovery of bodies like Pluto, Eris, and Sedna relies a lot on the good luck of looking in the right place at the right time. He suggested that had Eris's orbit been different, and had it been discovered only a few years after Pluto, that perhaps we wouldn't have this controversy over Pluto's status today. After all, when Ceres was discovered in 1801 it was thought to be a planet, but as soon as many other small bodies were discovered nearby it got demoted as well and became known as the largest asteroid instead. Had Tombaugh or others managed to find other Pluto-like objects in the outer solar system in the early twentieth century, then perhaps we wouldn't have this debate today. But, Brown acknowledges, he does prefer what really did happen, as otherwise he wouldn't have been the discoverer of Eris.

All in all, a lovely evening, and it was wonderful to have the chance to meet him.

Mike Brown's Message to Supporters of Pluto Mike Brown's Message to Supporters of Pluto
Photo ©2011 M. Burstein. All rights reserved.


In my heart, Pluto will always be a planet.
As in ours.
Pluto IS still a planet in a lot more than just people's hearts. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Hundreds of professional astronomers led by New Horizons Principal Investigator Dr. Alan Stern signed a formal petition rejecting the IAU definition and the demotion. The New Horizons mission continues to refer to Pluto as a planet. This is an ongoing debate with two equally legitimate views. Brown's is the dynamical planet definition. The alternative is a geophysical planet definition, in which a planet is any non-self luminous spheroidal body orbiting a star. In other words, if the object is large enough to be rounded by its own gravity, a state known as hydrostatic equilibrium, and it orbits a star, it's a planet. By this definition, Ceres is a planet, as are Pluto, Haumea, Makemake, Eris, and any other dwarf planet large enough to be spherical. Dwarf planets are simply a third class of planets in addition to terrestrials and jovians--objects orbiting a star and large enough to be spherical but not large enough to gravitationally dominate their orbits.
It's a shame you couldn't stick around for the Q&A. There were some good questions, and I accidentally triggered a rant by mentioning the "14-planet" definition. "If your definition is 'round things' you have to admit there are about 200 of them!" He was sympathetic to the "4-planet" definition though.
It would have been nice to stay for the Q&A, but he was very understanding about our reasons for leaving. He has a young daughter, so he knows what it is like for us to need to get home.

I wish I could attend his 4 pm talk today at Boston University, though.

Is the "4-planet" definition the one that defines the solar system as four planets (Jupiter, Saturn, Uranus, and Neptune) plus debris?
"Debris" is in fact the exact word he used. Apparently in a past class about planetary formation, long before all this, he attempted to get his students to agree to that definition with no luck at all.
I think Isaac Asimov was one of the first to use that definition, including the word "debris."
Mike and Nomi, can I count on the two of you to come to my book talk and accept an autographed copy of my book "The Little Planet That Would Not Die: Pluto's Story." There is a preview of it in the Dec. 16, 2010 "Atlantic" here: http://www.theatlantic.com/technology/archive/2010/12/the-argument-for-pluto-why-the-tiny-dwarf-is-still-a-planet/68123/

I hope to have the book out and being doing a book tour by the summer.
Whether or not we can attend is really going to come down to babysitting availability. We've had to miss a lot since the kids arrived.

(And as I've mentioned before, I never go by Mike, always Michael.)
Oops, my mistake. Michael it is. I will do my best to let you know the date of my talk as far in advance as possible. And I will be happy to pay for a babysitter. It just wouldn't be the same if the two of you weren't there. I'm guessing the talk will take place around the time we have air conditioning weather.
He also wrote two books on Pluto
(noticed while changing the subject heading to dwarf planet...)

Asimov, Isaac. How did we find out about Pluto? illustrated by Erika Kors. New York : Walker and Co., c1991.

Isaac Asimov; Greg Walz-Chojnacki. A double planet? : Pluto and Charon. Milwaukee : Gareth Stevens Pub., 1996. (this must be a later edition but I can't find an earlier version)
I think I own a copy of the first one, somewhere.
What's wrong with having 200 planets in the solar system if that is what we have? Memorization is not important; we don't ask kids to memorize the names of all rivers on Earth or all the moons of Jupiter. It's more important that they learn the different types of planets and the characteristics of each type.
Nothing, but I'm not sure it actually makes sense to have big stuff like Jupiter and Saturn in the same categroy as pluto. If you lay out the properties of various objects pluto and eris just don't quite fit in the same categrory.
I'm not sure it makes sense to have Jupiter and Saturn in the same category as Earth either. In fact, Earth is more like Pluto and Eris than like Jupiter and Saturn. Earth, Pluto, and Eris all have solid surfaces and are mostly rocky (Pluto is estimated to be 75% rock) while Jupiter and Saturn have no solid surfaces and are composed chiefly of hydrogen and helium, like the Sun. They even have their own "mini-solar systems" going. Both Earth and Pluto have nitrogen in their atmospheres, and both have large moons formed via giant impact.

Dr. Mark Sykes, at the 2008 Great Planet Debate in Laurel, MD, when asked about the differences between the larger planets and the dwarf planets, humorously said, "that's why God invented subcategories." Being different does not make objects not planets; it just makes them different kinds of planets. Dwarf planets should simply be considered a subclass of planets referring to small objects in hydrostatic equilibrium that are not large enough to gravitationally dominate their orbits. As we find more and stranger exoplanets, I expect to see more and more subcategories of planets added.
It seems like we should have 4 subcategories:

1) Gas Giants (Jupiter and Saturn)
2) Ice Giants (Uranus and Neptune)
3) Terstrial Planets (Earth etc)
4) Dwarfs

Honestly I don't have a huge problem with pluto's demotion. It never fit with the big 8 on a number of fronts.
I agree with your first statement, but not with your second. What is wrong with all the subcategories being considered planets. "The big 8" don't necessarily fit with one another either, and chances are the exoplanets we find may not be like anything we know.
Other than the emotional resonance, what is the importance of the issue? There are no real scientific implications to what's defined as a planet, are there?
Actually, there are real scientific implications. First, it makes no sense to have a "definition" imposed mostly by people who don't study planets at all, an act that was largely politically motivated. At issue is the IAU definition's complete exclusion of geophysics in favor of a dynamical definition. What happens if we discover a Mars-sized object in the Kuiper Belt? We could end up with two identical objects classed differently just because of their locations. It does not make sense to define an object solely by where it is while ignoring what it is. Even Earth wouldn't clear its orbit if put in Pluto's position; this was calculated by Dr. Hal Levison. The IAU definition is inherently biased against planets further from their parent stars because these have progressively larger orbits to clear.
Sounds like an interesting evening. Glad you were able to get out for it. Don't you just hate it when your kids force a curfew on you? Children just don't understand. ;)

I recently gave another of my junior high presentations on the subject. I've been tweaking it each time, and seemingly receiving more and more favorable responses from the kids each time. I received some terrific thank you notes this time, with drawings of the solar system, lots of smileys, and a few hearts.

I have to admit that, while I do frame it in terms of the discovery of Pluto and the change in its official status, I've started using that more as a stepping-off point to talking more about how children can influence big science. I need to do a post about the event on my LJ, but have been too busy to get to it. Maybe this weekend.

December 2016

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