EARLIER FEATURES

FEATURES CONTENTS

LATER FEATURES

THE WAR OVER PLUTO

Brian Grainger

brianATgrainger1.freeserve.co.uk

You may have read in the news recently that the International Astronomical Union, (IAU), have recently decided on a definition for a planet that removed planet status from Pluto. It would seem this is a devastating turn of events, especially for Americans. I would have thought this quite mundane news, but it seems to me that the American reaction only confirms my suspicions that the world is going slowly gaga. More seriously, it undermines science.

May I say at the outset that I have nothing against America or its people. I rather admire the fact that, unlike the UK, they have a constitution and bill of rights that tends to protect them from the more lunatic tendencies of its leaders.

First, a bit of history. The first eight planets: Mercury; Venus; Earth; Mars; Jupiter; Saturn; Uranus; Neptune have been known about for quite some time. Then, in 1930, Clyde Tombaugh, an American, discovered another far more distant object in our solar system. At the time it was known to share similar characteristics as the known planets, so it was natural to call it a planet. It was named Pluto.

Over the years, as science has advanced, it has become clear that Pluto is a bit of an oddball. Two things in particular make it particularly weird. First, its orbit varies so much that sometimes it is nearer to the sun than Neptune. Second, the orbit is highly tilted to the ecliptic. The ecliptic is an imaginary flat disk with the sun at the centre, on the surface of which the planetary orbits tend to reside. Each orbit does deviate a bit from the ecliptic. The ecliptic is defined so that Earth's orbit resides on it precisely. Going outward from the Earth to Pluto the orbits of the other planets are tilted by no more than 3° to the ecliptic - that for Saturn. Pluto's orbit, by contrast, has a tilt of over 17°!

As time has gone on further objects have been discovered in the outer regions of the solar system, which is now known as the Kuiper Belt. The Kuiper Belt is a bit like the Asteroid Belt, thought to be made up of various sized objects that are not planets in their own right. In 1978, Pluto was found to have companion, which we regarded as its moon, called Charon.

As knowledge of the Kuiper Belt and its inhabitants was gained it became more and more obvious to some astronomers that Pluto was not really like all the other known planets at all. Astronomers began to question whether it really was a planet.

It was then realised that there was no definition of what a planet was, so it was hard to say whether Pluto fitted the bill.

It was decided that the IAU should form a committee and come up with a definition. This they did and they failed to agree on a definition!

Then in 2003 something major happened. An object was found in the Kuiper belt that was bigger then Pluto! Its official name, at the moment, is 2003 UB313. That is hardly snappy enough for the tabloids so it has been called Xena, (after the Warrior Princess). The problem now was, if it is bigger than Pluto, is it a planet?

The IAU decided to form another committee and come up with a definition for a planet, that was to be voted upon at their major congress in Prague in August 2006. They had quite some time to think about it and during the period the 'Pluto is a planet' supporters were vocal. The main argument seemed to be that as schoolchildren had grown up being taught that Pluto was a planet, it was not possible to change its status now. All those textbooks would have to be written - the people would just not accept it - what about that dog that Disney christened Pluto! All very scientific!

The IAU committee deliberated and came up with their definition, which was released to the public just before their congress. The tried to appease everyone, including the 'Pluto is a planet' supporters. They came up with a proper scientific definition that can be paraphrased as follows:

Note that I have simplified this a bit and deliberately left out the definition of a satellite, which was in the original proposal.

Clearly, by this definition, Pluto was a planet, so everyone would be happy - they thought. Unfortunately, it meant that 2003 UB313 was also a planet - so was Charon and, bizarrely, so was Ceres, which was previously the largest known Asteroid. Charon, was no longer a satellite of Pluto because they actually formed a pair that both rotated about a point that was at some point between them. The other problem was that as more objects got discovered in the Kuiper Belt they would become planets.

My feelings on this were that the definition was at least scientific. I don't really believe Pluto should be classified as a planet but was prepared to accept it, if everybody else would. The bit about Charon and Pluto was news to me but it made sense, if Pluto was a planet. It was the planetary equivalent of a binary star. The bit about Ceres becoming a planet was a bit harder to swallow, but I justified it on the basis that at least now Kepler's laws of planetary motion would be fully vindicated. The application of Kepler's laws led to the deduction that a planet should exist where the Asteroid belt is. Now there would be one!

There was a week to go before the big vote and there was a lot of discussion outside the congress. It was clear that there were serious reservations to the proposal and one group proposed a new definition by modifying the original. This group of 18 individuals came from various countries of Europe and South America. There was only 2 from the USA.

This new proposal, again simplified, said:

Under this definition Pluto would not be a planet, because of proviso (b). The only planets would be the 8 classical ones I listed at the start.

Clearly this proposal struck a chord with the committee. They could see there was a lot of disquiet and they were now trying to find a way to backtrack and find a definition that removed Pluto as a planet.

Ultimately they came out with a similar proposal, that is simplified as:

This new proposal also left the 8 classical planets as the only planets. Pluto was a dwarf planet, and in a separate proposal was defined as the prototype of a new class of objects called Trans-Neptunian Objects, (TNOs). It also made another change. Condition (a) meant it only applied to the solar system and NOT to other star systems.

Taken from: http://www.iau2006.org/mirror/www.iau.org/iau0603/iau0603a.html
Credit: The International Astronomical Union/Martin Kornmesser

My views on this proposal was that it was not very scientific as it left some open questions.
E.g. How round is nearly round; how does one define 'cleared' and the 'neighbourhood of an orbit'.
However, it came out with the conclusion I agreed with! I also recognised that it was crafted in a very short time scale and did not allow enough time for comment.

This final proposal was voted upon and passed.

Immediately, the protests started.

First off, a petition appeared on the web at:
http://www.ipetitions.com/petition/planetprotest
This stated that the signatories would not accept the definition because it had serious technical and pedagogical flaws, was not subject to critical review and was only voted on by 400 out of 10000 members of the IAU. They asked for a better definition.

Note that they were not arguing whether Pluto was a planet or not, just with how the definition was arrived at. Virtually all the signatories were from US institutions. Is there a split between the USA and the rest of the world appearing?

Now, things really started to go weird.

The Legislature of California decided to discuss the decision of the IAU and concluded that:

'Resolved by the Assembly of the State of California, That the Assembly hereby condemns the International Astronomical Union’s decision to strip Pluto of its planetary status for its tremendous impact on the people of California and the state’s long term fiscal health.'

You can read the resolution at:
http://www.leginfo.ca.gov/pub/bill/asm/ab_0001-0050/hr_36_bill_20060824_introduced.pdf
Here are some extracts.

WHEREAS, Pluto was discovered in 1930 by an American, Clyde Tombaugh, at the Lowell Observatory in Arizona, and this discovery resulted in millions of Californians being taught that Pluto was the ninth planet in the solar system;

WHEREAS, Pluto, named after the Roman God of the underworld and affectionately sharing the name of California’s most famous animated dog, has a special connection to California history and culture;

WHEREAS, Downgrading Pluto’s status will cause psychological harm to some Californians who question their place in the universe and worry about the instability of universal constants;

WHEREAS, The downgrading of Pluto reduces the number of planets available for legislative leaders to hide redistricting legislation and other inconvenient political reform measures;

Now, it is hard to know whether this resolution is a rare example of the USA trying to be ironic. Even if it is then the conclusion is serious enough. I conclude from this barminess that (a) one should NEVER let politicians decide scientific problems and (b) the state of California is not getting value for money from their local taxes. Their politicians have got time to discuss things that don't concern them.

Next up to condemn the IAU was New Mexico State University, where Clyde Tombaugh lectured for many years. A protest rally occurred at the beginning of September, which was reported here:
http://www.nmsu.edu/~ucomm/Releases/2006/september/pluto_protest.htm

Now it says the rally was good-natured and I am sure it was. Nevertheless, here is what Herb Beebe, Professor Emeritus of Astronomy said:

"Clyde Tombaugh was an American hero," he said. "For that reason alone, Pluto's status as a full-fledged planet should be kept."

Now, I think Clyde Tombaugh should be lauded for discovering the first Kuiper Belt object, long before any further discoveries. However, the fact that he is American has no bearing on whether his discovery is a planet or not. That is not science.

Now the reclassification of Pluto has given workers on the New Horizons project for NASA a bit of a problem. They spent a number of years lobbying NASA to send a probe to Pluto, the last uncharted 'planet' of the solar system. Only last year the probe was finally on its way. Now, it is not going to a planet at all. On September 6th, Alan Stern, the leader of the project, wrote at:
http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_09_06_2006.php

I think Alan Stern should be proud that his probe is on its way to the first Kuiper Belt object to be visited. However, the fact that a probe is going there is no reason for demanding planet status for Pluto.

Following in the footsteps of California, the City of Madison Legistar has seen fit to issue a proclamation that Pluto is the ninth planet and condemning the IAU for not tolerating diversity - because they classified Pluto as a dwarf planet. You can see the full text of the proclamation at:
http://legistar.cityofmadison.com/DetailReport/Reports/Temp/972006122548.pdf
(so I am told - the web site was not responding when I tried).

I am still waiting to read of some protest from outside the USA. Is this really a dichotomy between the USA and the rest of the world?

As I said above, I don't think the current planet definition is very scientific. It was very rushed and needs more work. I think even the IAU recognise that. Nevertheless, it is what we have for the moment and it is better than nothing. We should accept it and get on with furthering our understanding of our solar system by scientific method and not emotive argument.

It is heartening to note that there is some sanity in North America, albeit from Canada rather than the USA. Brian Fenerty has already highlighted the problem with the current planet definition and made a positive suggestion to start the discussion. Have a look at the following to see it:
http://www.telusplanet.net/public/fenertyb/amendiau.htm

I wrote the above a little while ago. In the intervening time two things have been made known that cement the new status of Pluto.

First off, on September 7th, the Minor Planet Center gave Pluto its asteroid number, 134340. The Minor Planet Center is responsible for keeping the lists of known asteroids. They also labelled 2003 UB313 as asteroid 136199. Of course, Ceres had long ago been given the number 1. The director of the Center also added that the assignment of these numbers did not preclude the possibility of objects gaining other numbers if separate lists were formed at a later date, for TNOs say.

Finally, on September 14th, the IAU officially announced the name of 2003 UB313, which had unofficially been known as Xena.
http://www.iau2006.org/mirror/www.iau.org/iau0605/index.html

Following a recommendation of the discovery team, 2003 UB313 was to be named Eris. Mike Brown, member of the team, said this name was too good to pass up. Why? To quote from the IAU announcement:

That truly reflects the effect on the astronomical community since the discovery of Eris. First the Trojan war - now the Pluto War!

TOP