Mike Brown told EarthSky that it wasn’t his goal to kill Pluto. The Caltech astronomer has discovered hundreds of objects in the outer limits of our solar system, but it was his discovery of the dwarf planet Eris that caused International Astronomical Union to demote Pluto from a planet to a dwarf planet in 2006. Brown is the author of How I Killed Pluto and Why It Had It Coming. He spoke with EarthSky’s Jorge Salazar.
Pluto was demoted from planet status in 2006, but still, year after year, voices clamor to reinstate Pluto.
That fact that it keeps coming up year after year after year is because there will always be people who have, whatever the reason, an interest in reinstating Pluto as a planet.
Dwarf planet Eris. Image Credit: NASA/JPL-Caltech
And you’ll always hear from them, because it’s always an interesting story when somebody jumps up an down and says Pluto should be a planet again. It’s a less interesting story to say, yep, this year we still think Pluto is not a planet. But from what I can tell, from talking to astronomers and going to conferences with astronomers who study the outer solar system, like I do, there are very few people in the astronomical community who think that there’s any reason whatsoever to revisit what planets are.
Why did Pluto – as you say in the book’s title – “have it coming?”
The solar system consists of eight very large dominant things that define it. They’re the architecture of the solar system, these eight dominant objects – the planets – that are surrounded by little bits of debris that are going in and out of their orbits. What led to the demotion of Pluto was the realization that Pluto is not this unique object in the solar system, in the way that the eight planets are. It’s really part of this whole field of debris.
You see these images of the solar system where there are nine planets that are more or less the same size. You see Jupiter as a little bit bigger than the Earth, and the Earth a little bit bigger than Mercury, and Mercury and Pluto about the same size. That view of the solar system is thoroughly incorrect. It’s just not the way the solar system really looks. If the solar system really did look that way, even I would think that demoting Pluto didn’t make sense.
The real deal of the solar system is that Jupiter is huge compared to anything else out there. The Earth is much, much smaller than Jupiter. And Pluto is even tinier still. It’s half the size of our own moon. Getting people to see that correct impression of the solar system, the real solar system instead of the cartoon solar system, I think is an incredibly important part of astronomers trying to educate the public.
So I think not only did Pluto have it coming in the sense that it never was a big and important part of the solar system, but it actually matters a lot that we explain this to the public, that we educate people on what their universe is actually like.
The media in 2005 initially heralded your discovery of Eris as the tenth planet. Given the fame of discovering a new planet around our sun, were you ever tempted to be on the side of ten planets versus eight?
When we first discovered Eris and knew that we had something of the size of Pluto or perhaps larger, my first response was, of course it’s a planet – because Pluto’s a planet and anything bigger is clearly a planet too. It never occurred to me that astronomers would have the courage – I think courage is the right word – to demote Pluto. Because astronomers, like everybody else, have this nostalgic feeling about Pluto.
I tried to think about this, and I finally came to the right conclusion. But at first I thought, okay, it doesn’t matter. If Pluto is going to be a planet, Eris can be a planet. There can be ten planets, and we don’t really need a scientific definition of the word planet. To have Pluto and Eris be called planets, you just have to give up on science and say, well we called them planets because a planet doesn’t really mean anything and that’s what we want them to be.
It’s kind of like the word “continent.” The word continent doesn’t actually mean anything. Continents are the things we say we are. And planets could be the same way. It would mean that I got to discover the tenth planet. But that would mean that there was no good scientific definition for the word planet. And that didn’t seem so good. In the end, when astronomers started grumbling about some of the proposed definitions and finally got together and considered kicking Pluto out – or actually kicking the one I had discovered out and Pluto along with it – it became clear that astronomers really were going to try get together and actually have the determination to do this, I was thrilled. Even though I lost Eris as the tenth planet, I suddenly realized that I had an opportunity to actually make a scientific definition of the word ‘planet’ that described the solar system correctly.
And it’s such a beautiful thing. The solar system is arranged in such a beautiful way with these eight dominant things, and everything else flitting around between them, that if we can have our cultural view of what the solar system is mesh with the scientific view, I would gladly trade my discovery of the tenth planet for really furthering the overall world’s understanding of how the solar system is. I’m very happy with the way it worked out.
What projects are you working on right now?
The big survey we did that led to the discovery of Eris and many of these other objects all came from a telescope, the Palomar Observatory outside of San Diego. From the Palomar Observatory you can only see the northern parts of the sky. You can’t see the southern parts of the sky. So it’s taken us a couple of years to get there, but we’re now finally surveying what might be in the southern parts of the skies, and we don’t know what there is to find down there.
The other project that I’m most excited about these days came from another discovery that was in our big survey, which was the discovery of the object called Sedna. Sedna is the object that we found that goes the furthest away from the sun. It has this incredibly looping, 12,000 year obit around the sun. We’ve only found one object like it, but we know that there must be many more out there, if we can just find them. The problem is that they have such looping orbits and they’re so far away that they’re incredibly difficult to find. We’ve been trying, with some of the biggest telescopes on the Earth to try to find these.
The reason we want to find them is because these objects that are so far away are essentially little frozen relics of the earliest times of the solar system. They’re frozen relics in the sense that their chemistry but also in the sense of their orbits around the sun. So if we can find more of these relics, we would have these fossils from the birth of the sun, we can try to actually read this fossil record. So that’s another of these very exciting projects that we’re working on these days.
What’s the most important thing you want people today to know about Pluto?
I’d say the most important thing to know about Pluto is that in the scale of the solar system, it is insignificant debris. And I say that fondly. The eight planets dominate everything that goes on. Pluto and all the other things like Pluto are simply dominated by these eight planets. They’re kicked around. They’re on these crazy elliptical orbits, and tilted obits, whereas the planets are on these nice, stately orderly orbits on the inside. Pluto is not this special planetary-class object out past Neptune. Pluto is just one of many, many things like it. In the grand scale of the solar system, it’s just a little speck of debris.
I, for one, would like to see Pluto be a planet. It has a moon, unlike Venus or Mercury.
I believe there have also been some asteroids discovered that have “moons”, insofar as having other chunks of material orbiting around them. Not to say Pluto should or shouldn’t be a planet, but having a moon or not shouldn’t be the defining factor.
I can see both sides of this, but ultimately in the field of astronomy science should win over public opinion, and so if the classification has changed and is agreed upon by the scientific community, then so be it.
“But from what I can tell, from talking to astronomers and going to conferences with astronomers who study the outer solar system, like I do, there are very few people in the astronomical community who think that there’s any reason whatsoever to revisit what planets are.”
This is an outright lie, and it is extremely disingenuous for Brown to make such a claim. As an astronomer myself, I talk to many astronomers and attend conferences and can vouch for the fact that astronomers’ opinions remain divided on this matter. Both the dynamical planet definition, which Brown espouses, and the geophysical planet definition, which supporters of Pluto’s planet status uphold, are equally legitimate views of the solar system. The problem with the dynamical view is that it looks only at where objects are while ignoring what they are. The further an object is from its parent star, the larger an orbit it has to clear. If Earth were in Pluto’s orbit, it wouldn’t clear that orbit either. So the IAU definition, which even Neil de Grasse Tyson described as flawed, presents the absurdity where the same object can be a planet in one location and not a planet in another. In contrast, the geophysical planet definition is based on what individual objects are rather than where they are or how they relate to other objects. Pluto is more than a “speck of debris” because it is large enough to be rounded by its own gravity, a characteristic of planets and not of shapeless asteroids. Asteroids are mostly loosely-held together rubble piles. Objects large enough to be spherical are complex worlds with geology and weather.
One could easily say that Earth has more in common with Pluto than with Jupiter. Both Earth and Pluto have solid surfaces; both have nitrogen in their atmospheres, and both have large moons formed via giant impact. In contrast, Jupiter is composed mostly of hydrogen and helium, like the Sun, is gaseous, and has its own “little solar system” going. How can Brown justify putting Jupiter and Earth in the same category but Earth and Pluto in different categories?
The four percent of the IAU who voted on the controversial demotion were mostly not planetary scientists, and their motives were largely political as well as based on an error. Eris is not larger than Pluto, as previously believed. This was determined through Eris’ occultation of a star in Nov. 2010.
The scientific community clearly has not agreed on the IAU definition. Hundreds of professional astronomers signed a formal petition rejecting the IAU decision and subsequently asked the IAU to revisit the issue at its 2009 General Assembly. The IAU leadership adamantly refused, and almost all these scientists boycotted the assembly as a result. That hardly counts as consensus.
From the other point of view, I am writing a book “The Little Planet That Would Not Die: Pluto’s Story,” which I expect to be published later in the year. I hope you will consider doing a podcast with me or with someone else representing the other side of this debate.
Hi Laurel,
Thanks for writing. Astronomer Alan Stern has another side of the Pluto debate, http://bit.ly/gFQasE. Best – Jorge
Thanks, Jorge! I’ve seen this page by Alan Stern.
One correction: My name is Laurel, not Laura.
My apologies! Best – Jorge
Here’s a great news story of a non-planet with moons just out today, a visualization of asteroid Kleopatra with moons Alexhelios and Cleoselene http://newscenter.berkeley.edu/2011/02/22/how-kleopatra-got-its-moons/ .
How on Earth no journalistic entity allows Mike Brown to claim full credit for discovering Eris is beyond me. The dwarf planet, now thought to be smaller than Pluto and soon to be verified as smaller once Bruno Sicardy’s scientific paper on the recent stellar occultation of it seen from the Chilean Andes is published, was co-discovered by Mr. Brown with Chad Trujillo and David L. Rabinowitz, who believes Pluto is still a planet, by the way.
If EarthSky would bother to do a bit of research before publishing articles, you would know this. Please make the correction now. Better late than never.
Thank you.
Mike Wrathell, Esq. & Artist
I mean, “How on Earth any journalistic entity allows Mike Brown to claim full credit for discovering Eris is beyond me.”
To call Pluto a little speck of debris is absurd. Pluto has at least 3 moons and may have life under an ice-covered ocean. Why Mr. Brown has chosen to write a book about a planet he obviously has utter contempt for, and apparently also an astounding degree of utter ignorance is beyond me. He should write about objects he has co-discovered, not about planets that make his co-discoveries look like the space junk that they apparently are, if we listen to him, which, as I have pointed out, is something that should be done in league with one’s own research, as he is given to misrepresentation and ignorance.
Anyone notice how just about when Pluto got demoted was when the whole thing about a large moon being vital to life on earth started . And that moons like Earth’s moons are very rare and that some morons using that as a way to try and convince the gullible and weakminded that life harboring planets are extremely rare. One only needs to look at Pluto’s moon Charon to see that Earth-moon systmes rae not rare at all. Not to mention that a double planet system or planet-large moon(whatever you wanna call it0 has been discovered in a different star system proving large moons are not rare at all. Furthermore the whole Earth would be tidally locked without its moon is BS too. Mars has really small moons and Venus no moon at all and neither are tidally locked. I also don’t buy the whole Mars lost it’s atmosphere and magnetic field due to it’s small size either. In fact there is very strong evidence that a huge asteroid likely thousands of years and certainly no more than a few million years ago)not billions of years ago) hit Mars and is likely what cause Mars atmosphere and magnetic field to deteoriate. Not to mention there is evidence that Mars atmosphere and magnetic field is coming back proving the BS that Mars lost its atmoshpeher and magnetic field billions of years ago due to it’s small size to be completely untrue. All this BS I think is just to try and brainwash the gullible and weak min ded into believing earth is a special and unique planet when it is really not a special and unique planet at all and is likely inferior to many planets out there and our sun and solar system is likely inferior to lots of stars and solar systems out there Besides look at the pictures of Mars and our moon as well as Saturn’s moon Titan and you will see that life still exits and that intelligence life once existed and as a matter of fact may even still be on our moon. I also strongly believe intelligent life once existed on Venus but was likely wiped out by extreme volcanism. I also don’t at all believe for a second that a planet has to be just like earth for life or even intelligent life to exist. I believe that life and yes even intelligent life could exist on gas planets and even stars.
BTW I forgot to say it in my post above but you could probably figure it out anyway that the fact Pluto has such a large moon is probably the real reason it was demoted so Never a straight answer(N ASA) the Rare Earth retards could then use the excuse that a large moon which they say is vital for a planet to have life which I BTW think is BS too, is extremely rare when it is not rare at all. After all they figured if they demoted Pluto noone would care about it anymore and wouldn’t use Pluto and it’s moon Charon to prove planets with large moons are not rare. Wake up people. You are being brainwashed. Life is extremely common in the universe. Never a Straight Answer,l the government and the religions that plague this planet is lying to you to hide the truth
Yes. Mr. Brown had his reasons. I would have to disagree with the man, but he had his reasons. One day a black cat crosses a street, and something bad occurs. The person relates that bad incident due to the black cat. However, the black cat crosses the street several times a night…several times a week…several times a month; but just one bad incident. Does that mean the bad incident is related to the black cat? or maybe not?
Pluto Strikes Back
Cancel the Webb telescope. Teach them not to lie about the costs.
In fact, cancel all astronomy funding until Pluto is reinstated as a planet.
Astronomers with their elitist ivory tower snobbery intentionally went out
out of their way to change the definition of a planet to exclude Pluto.
They can just as easily admit a mistake, apologize and change the
definition once again to include Pluto (old coke, new coke, old coke).
The astronomy community knew the public would be offended, even
outraged and they went ahead and with it anyway. Now they want more
public money. This churlish ungrateful attitude needs the same lesson
National Public Radio and the National Endowment for the Arts got.
Also astronomy unlike NPR and NEA isn’t even mildly entertaining.
Pluto not a planet means astronomers not employed.
Pluto=planet=astronomy funding