Wednesday, September 17, 2008

Now all five dwarf planets have real names!

Amidst unresolved issues regarding the circumstances of its discovery, the big and weird Kuiper Belt Object 2003 EL61 has been named Haumea and is now listed as the 5th dwarf planet, joining Pluto, Eris and Makemake in the Kuiper Belt and Ceres in the main belt of asteroids; no further immediate candidates for ascension into this category of solar system bodies introduced only in 2006 are known. The two satellites of Haumea are now called Hi'iaka and Namaka. While the IAU refrains from saying anything about the discoverer(s) of Haumea, the USGS in its list locates the discovery telescope in Spain (where it was imaged but not recognized in 2003) yet also names no people. Mike Brown, who hit upon the same body in 2004, realized that it was something important and is generally credited with the discovery, meanwhile in great detail reiterates his claim of being the rightful owner of this dwarf planet. And indeed the IAU used his 2006 proposal for the name.

In other news this image may be the first one of comet P17/Holmes after its conjunction with the Sun, though it shows only the very core of the coma. • An interesting animation based on Metop data shows how the Kasatochi aerosols swept around the globe - so these weird post-sunset colors imaged by yours truly from Eastern Germany on Aug. 19 could already have been caused by them (which also goes for more German sunset views from that day, this August view from Colorado or another German view of Aug. 30). • Australian views of the evening planets on Sep. 13 and Sep. 1. • Another story on the September Perseids outburst. • New insights into the 19th century eruption of Eta Carinae. • And a view of overlapping galaxies from Hubble - where NICMOS is down and only the WFPC2 working now among the main instruments.


Laurel Kornfeld said...

If this object is a dwarf planet, then it is a planet. I'm assuming that in giving it dwarf planet status, the IAU has confirmed it is in hydrostatic equilibrium. It's far more important that the definition stating that dwarf planets are not planets at all be overturned than that we find out who discovered EL61 first. An object in hydrostatic equilibrium orbiting a star is a planet. Mike Brown will have to make the argument in favor of EL61's planet status after all, whether now or in 2015.

Daniel Fischer said...

Mike Brown has already taken care of this comment in his blog; nothing to add from my side.

Laurel Kornfeld said...

But in his response to me, even Brown acknowledged he would be okay with a broader planet definition that allows dwarf planets to be considered a subclass of planets.

Daniel Fischer said...

What Brown said in his blog was: "The 8 planets are significantly different than the many many dwarf planets. Once that distinction is made, I don't care what you call them." How that statement could be understood to mean that "he would be okay with a broader planet definition that allows dwarf planets to be considered a subclass of planets" is beyond me.

Actually, I don't care either too much and would have been happy with many possible outcomes of the planet definition procedure (though not the initial proposal that was just too weird). But what I cannot let stand are the constant misrepresentations of how the current (and already widely used) definition came to be, but those who weren't there while I was.

Laurel, I note that you are an activist for the Obama campaign - hooray to that! How about a truce with regard to those distant may-be-or-may-be-not-planets and concentrating on saving *this* planet for now ... For if that other guy wins in November, it could be blamed in a small part on you concentrating too much on fighting the IAU than on fighting him.

Laurel Kornfeld said...

Daniel, Mike Brown also said: "Laurel: You might be surprised to learn that I would be perfectly happy if you called dwarf planets 'planets.' But, of course, I am also perfectly happy if you do not.

To me, this statement makes it quite clear that Brown would be okay with a broad planet definition that includes dwarf planets as a subclass of planets. So going back to the 2006 General Assembly, that means he would support Resolution 5a, which established the distinction between classical planets and dwarf planets but at the same time could also support Resolution 5b, which had it passed, would have established dwarf planets as a subclass of planets. To me this option addresses both dynamical considerations in its definition of the eight classical planets as well as geophysical characteristics by recognizing that even if objects are not gravitationally dominant, those in hydrostatic equilibrium are still planets.

I don't see what the problem was with the initial IAU 12-planet proposal either. Is your opposition to it due to its inclusion of Charon? Pluto-Charon are essentially a binary dwarf planet system. And that resolution had been properly vetted by the appropriate committees, unlike the ones that replaced it, which were done in real time in violation of the IAU's own bylaws.

If by a truce you mean we agree to disagree about what happened at the General Assembly and the resulting planet definition, that's fine with me. However, I stand by my statement that both the process by which this definition was adopted and the outcome (defining dwarf planets as not being planets at all and classifying objects solely by where they are rather than by what they are) were highly flawed and must be revisited. I absolutely intend to continue fighting for the reversal of this decision, and if that means fighting the IAU, so be it.

I'm guessing your remarks about the presidential election are tongue in cheek, as blaming a potential McCain victory on me spending too much time fighting the IAU is far fetched to say the least. Don't forget we've also had extensive voter fraud and "stolen elections" in this country (though not in my state), in which the will of the people was overturned.

I support Obama, but I support the planet status of dwarf planets as well and will continue to do so. It is not a matter of either/or but both/and.

Daniel Fischer said...

"We could call the 8 big things 'grogs' and the other 50 round things 'bloogs' and it would not matter to me." See the word "other"? What's important to Brown - who discovered (or, what the heck, co-discovered) several of the biggest of the "other 50 round things" and studied them in great detail, so he's the most qualified one on this planet to classify them - is that these bodies are distinct from the "8 big things".

And much of the astronomical world has come to agree with that. One might debate whether the "other 50 round things" are sufficiently different from the other hundred thousands of not so round things going around the Sun to deserve a class of their own - which no one seemed to find necessary before 2006. But those planetologists who think the new class was not necessary (and I know a few) are not making so much noise ...

Laurel Kornfeld said...

Brown says he is okay with either form of classification as long as it distinguishes the objects that are gravitationally dominant from those that are not. His comments indicate he takes a neutral position regarding the issue of whether dwarf planets are classified as a subclass of planets.

Even if much of the astronomical world agrees with this, that does not mean that much of the astronomical world agrees that dwarf planets should not be considered a subclass of planets. We are talking about two separate issues here: gravitational dominance is one, and geophysical composition of an object is the other.

Brown may take a neutral position here, and he is certainly qualified, but I don't know that I would say he--or any specific individual-- is the most qualified person on this planet to make these judgments. There are many planetary scientists who believe that dwarf planets should be considered a type of planet, and a few of them, such as Dr. Alan Stern, Dr. Mark Sykes, and Dr. Hal Weaver, could be considered to have as much expertise in this area as Brown.

The creation of a new class of dwarf planets is not the problem per se. The problem is, to restate, the failure of resolution 5b and the subsequent blurring of dwarf planets with asteroids and other non-round objects. Most planetary scientists do not believe that distinguishing between objects in hydrostatic equilibrium and shapeless asteroids is something up for debate. The difference is very clear. Objects in hydrostatic equilibrium are differentiated and have the same geological processes as planets. Differentiating between these objects and inert asteroids is as important as is distinguishing between the eight gravitationally dominant objects and the others that do not dominate their neighborhoods.

Daniel Fischer said...

Being in hydrostatic equilibrium or not may actually be less important (and indeed was not a decisive factor in classification issues before 2006, AFAIK) than other factors in making a solar system body interesting.

Just have a look at this fine collection of the small and even really small bodies we've seen up close so far, all way below any "dwarf planet" cut-off yet stunning worlds of their own.

Laurel Kornfeld said...

I'm not arguing that objects not in hydrostatic equilibrium are any less stunning or worth studying than those that are. What I am saying is that this difference is important to note in classification schemes. If it wasn't a decisive factor prior to 2006, that's because we only recently discovered the Kuiper Belt and the fact that there are two types of KBOs--round ones and non-round ones. The new data requires us to take another look at the importance of hydrostatic equilibrium if we are going to start differentiating between subclasses of planets.

Daniel Fischer said...

It had been known for decades that beyond a certain diameter a solar system body of 'normal' composition, be it an asteroid or planetary Moon (or Kuiper Belt Object), would take on a more or less spherical shape under its own gravity. I don't recall the actual limit in the literature back then, could have been 400 or 500 km.

Thus the sphericity of Ceres was known for a long time (and also demonstrated directly by its photometric constancy) - yet I don't recall a single scientific paper (let alone a publuc "petition") calling for Ceres to be called a real planet again, a status it had lost, for good, in the mid-19th century. Nor was there any call to invent a new category for round bodies not dominating their neighborhood.

Laurel Kornfeld said...

I question how long the sphericity of Ceres was really known. We do know that Hubble imaged it in 1995, definitively showing it to be round. Obviously, it's being spherical was not known in the 19th century. It's very likely that in general, the public back then knew a lot less about astronomy than today, when we have immediate flow of information around the world.

However, if you look at scientific papers by planetary scientists emphasizing a geophysical definition, for example, Alan Stern prior to 2006, it is clear these scientists view Ceres as a planet. Given what we now know, it is inaccurate to say Ceres lost that status for good, as there are many planetary scientists who view dwarf planets as a subclass of planets.

As we discover more diverse objects in this solar system and others, there will be more calls to create more categories to encompass their great variety. Years ago, before Ceres' roundness was widely known, we knew of only one round object not gravitationally dominant, namely Pluto. Now that we know there are many and that these objects have geophysical properties akin to those of planets, it is clear that a new planet category must be created to define them.

Daniel Fischer said...

Hi Laurel,

I can really recommend checking the facts before posting - and it's so easy with a certain Google thing (no need to even rush to a library). The sphericity of Ceres has been known for about half a century:

- no photometric variation (published in 1953)

- spherical shape established (1976)

- confirmed by radar (1979)

- confirmed by stellar occultation (1987)

No Hubble needed thus for this insight. And I remembered right: The threshold for sphericity for a typical solar system body is 400 km diameter indeed. And it was known for a long time, calculated from first principles, as a textbook excerpt with references way back shows.

Laurel Kornfeld said...


Thank you for these references. These dates are at least 100 years after Ceres was demoted from planet status in the 19th century (at that time, its roundness was not known). And there were astronomers such as Alan Stern, who stated prior to the 2006 IAU vote that Ceres should be reinstated as a planet. All this means is that in spite of observable data, astronomers left Ceres in the wrong (asteroid) category for decades. That is not exactly a ringing endorsement for a group such as the IAU.

Daniel Fischer said...

While Mike Brown takes care of the details (nothing to add there), one final look at the fundamental issue. What the minority of planetologists that considers the dwarf planets 'real' planets - and which does not include many of the key Kuiper Belt researchers, including the actual discoverer of the three Pluto brethren Eris, Haumea and Makemake - overlooks are both astronomical and one cultural arguments.

- The solar system isn't called a system for nothing: It's ingredients play certain roles in which the exciting early years of the system's evolution (with migrating planets and such) have put them. So we got eight dynamically isolated planets (we know about) with at best some scruff around them and at least two belts of many times the same small stuff in the same neighborhood. (There could be another mass-wise major asteroid belt waiting to be discovered in the Neptune trojan zones, by the way.)

- Whether it was wise or not to define those inhabitants of the belts which meet the hydrostatic equilibrium criterion as something special is controversial and wasn't even an issue pre-2006: Some asteroid researchers, e.g., do not consider Ceres or Eris different enough from the rest to deserve a special category. And non-hydrostatic worlds can still be exiciting enough (witness the small asteroids Itokawa or Steins). But by and large the newly introduced term "dwarf planet" has been accepted by educators and scientists alike (and generates already over 600,000 Google hits).

- The cultural argument is this: "Planet" has always meant something special to man, first deities, then major bodies in the sky, then major bodies per se. This, and not some lofty scientific argument, is the real reason why the plutophiles want(ed) Pluto to remain in the planet category! Yet every reasonable planet definition that would have kept it that way (by dropping the "dwarf" and making all the big belt bodies true planets) would have increased the number or planets dramatically and not even yielded a fixed number anytime soon. The term "planet" would have been devalued tremendously.

It is the last insight that makes so many people - who have thought about the issue for a while and weighed the arguments - eventually concede that Pluto simply cannot be a planet as the other eight and never was one. It's precisely for those who say good-bye to planet Pluto that the IAU in 2006 voted to have a special subcategory of dwarf planets, now called plutoids, with the sole purpose of honoring the former king of the Kuiper Belt (until beaten by Eris). A rare emotional move in astro-buerocracy, but apparently in vain ...

Laurel Kornfeld said...

I take issue with your claim that it is a "minority" of planetologists and Kuiper Belt researchers who want dwarf planets to be considered a subclass of planets. Upon what do you base this claim? Please provide evidence other than a claim that all or most of these people spoke to you personally. I will emphasize that one of Mike Brown's team of three, Dr. David Rabinowitz, signed Alan Stern's petition rejecting the IAU definition of 2006. So even the discoverers of these three dwarf planets have not achieved a consensus on this.

I suggest you visit where you can listen to some of the proceedings of the Great Planet Debate, a large gathering of astronomers, educators, and others who conducted this open conference specifically in response to the problematic IAU General Assembly in 2006.

Even astronomers such as Stern and Sykes acknowledge a distinction between the large planets that dominate their orbits (what Stern in his 2000 article calls "uber-planets") and those that are in hydrostatic equilibrium but do not dominate their orbits due to their small size (what Stern in the same article calls "unter-planets"). However, this distinction in no way precludes the "unter-planets" or dwarf planets from being classified under the broader umbrella of planets.

I disagree with your claim that defining objects in hydrostatic equilibrium that are located in belts is controversial. You seem to seriously devalue the distinction between these objects, which are differentiated geologically and have compositions and processes far more similar to those of the major planets than to the asteroids. Whether or not this was an issue prior to 2006 is irrelevant. Exoplanets were not an issue prior to 1995. New discoveries add to our knowledge and very often require us to consider additional factors we did not consider earlier when classifying these objects.

The number of Google hits the term "dwarf planet" has received does not indicate one way or another whether those looking up the term believe dwarf planets should be considered planets. I have looked up the term on many occasions, and there is even a web site titled "Dwarf Planets Are Planets Too" that will show up in a Google search.

Again, the issue isn't whether the term has been accepted by scientists and educators but how those scientists and educators understand the term. Even Stern is fine with the designation as long as dwarf planets are considered a subclass of planets.

Why do we need a "fixed" number of planets? Why do you believe the word planet is devalued if our solar system has several hundred of them? This is a subjective judgment, nothing more. We have billions of stars; does that make the term less special? Is it scientific to artificially limit the number of planets in our solar system because doing so is somehow more convenient for us? In discussion at the Great Planet Debate, very few people felt that increasing the number of planets dramatically would somehow "devalue" the term.

Many people recognize that Pluto is different from our other eight planets, but that does not mean that they come to your conclusion that Pluto and the other dwarf planets cannot be considered planets. Instead, many people have come to realize that there are far more types of planets than we had previously realized.

I don't really understand the arguments in your last paragraph. Are you claiming the IAU made a decision based on emotional factors? How do you explain that resolution 5b, which would have established dwarf planets under the broader umbrella of planets, failed by only a narrow margin? I don't believe the vote was to "say goodbye to planet Pluto" but to distinguish the two categories of "uber-planets" and "unter-planets."

Even many IAU members who voted for this definition admit it is flawed, vague, and sloppy, not one of the organization's finer moments. Many know the issue must be revisited. I believe the Dawn mission to Ceres and the New Horizons mission to Pluto will compel this revisiting. In that sense, yes, the IAU vote was indeed in vain.

Daniel Fischer said...

All points have been made (over and over again, actually) and I consider this thread closed. For the time being. For there's more than enough real astronomy out there ...