Thursday, May 22, 2008

What's in a name?--Pluto

Clyde William Tombaugh
February 4th, 1906 to January 17th, 1997

It has been over 78 years since of the discovery of Pluto [February 18th, 1930] by Clyde William Tombaugh.

Robert Roy Britt [] wrote:

The hunt for Pluto began in 1905 when Percival Lowell...hypothesized about the possibility of a Planet X in the outer solar system. Lowell died before Pluto was discovered. Clyde Tombaugh found it on Feb.18, 1930 in a concerted scan of the sky. Tombaugh compared two photographs taken at the Lowell Observatory and noted the object's movement against the background of stars.

Among the most significant developments related to Pluto was the discovery of the Kuiper Belt, Grundy told Since the first Kuiper Belt Object was found in 1992, more than 1,000 have been spotted, some roughly half as big as Pluto. Studies of the variety of objects out there "can tell us so much about the compositional, collisional, and dynamical environment Pluto inhabits today and when it was forming."

The original handwritten notes by Clyde William Tombaugh on the aged paper that wraps around the original photographic plates revealing Pluto.

Atlas 5 Rocket
Launch video

And after many delays the probe to Pluto was launched [named "New Horizons"] shortly before noon [CST] on January 19th, 2006. It has now flown past Jupiter and taking a nap for its arrival in 2016. Think a bit...what will you be doing during those years: Graduate, get married, do research--be dead? A lot can happen in ten years. Seriously, consider the course of human events as the probe silently heads for its objective: A changing Earth, wars, natural disasters, advances in medicine and revelations of the universe. Even original members of the Pluto team will change; some might pass. The instruments on board the craft will be outdated and many of the future will laugh at their crudeness..."How primitive they were in the early years of the 21st Century". Consider the hazards of the sojourn and structural fatigue on the craft. Indeed a decade of changes and challenges.

Now the controversy...

Sedna, a new planet or planetoid was discovered 13 billion km from earth. It is very red and may have a moon. Some say if Pluto is a planet then this object should be considered a 10th planet. Despite a somewhat tabloid approach to this discovery, the announcement of Sedna challenges the accepted definition of just what a planet is supposed to be. I had never given it much thought but some research provided interesting information as to a definitive definition and who decides on the definition. Apparently the IAU [International Astronomical Union] is responsible. All of this quest to come up with a definition has caused old debates to resurface [is Pluto a planet or part of the Kuiper Belt], puzzling questions regarding newly discovered bodies since 1995, or the nature of "brown dwarfs". And, it appears that the IAU or anyone else for that matter doesn't have an official definition. Normally and traditionally we assume that planets are the result of swirling masses of dust and gasses that finally cool and condense to form “planets”. It’s one of those situations where we know it when we see it. Nevertheless, the time has come for some group like the IAU to derive a working definition that would reclassify existing phenomena and provide something of an agreement.

In March of 2004 I wrote:

Well, the situation does thicken a bit for it reminds me of an event that happened some 6 years ago regarding the "planet" status of Pluto. Doubts were raised since refined data had drastically changed the initial statistics of Pluto leading to the newest conclusion that Pluto was about 1/6 the size of Earth—thus, was it to be considered a planet. The general public was aghast that Pluto would be dropped from being called a planet. As far as the public was concerned IT was a part of the planetary system—PERIOD. Now, the scientific community had to use its finest diplomacy and make a delicate balance between scientific thought and public relations. Guess who won—the general populace with some grumbling from the scientific community. Many are still scratching their heads pondering a better definition of a “planet”. The discovery of Pluto is somewhat fascinating in that it was the concept of Percival Lowell [remember the canals of Mars] who made the observation that Uranus and Neptune were slightly bumped around and that another celestial body might be doing the wiggling—"Planet-X". Well, Lowell died just before World War I and the work was turned over to Clyde Tombaugh who did find the object. Thus, in 1930, Pluto became a planet. It was later discovered that Pluto was not responsible for the odd movements of Uranus and Neptune and that Pluto was ice covered--more like a comet than a planet. So the debate continues. All of this is to point out that some sort of definition needs to be established. And Pluto will remain a planet despite alternate evidence and much doubt...a part of the romance and cultural heritage of astronomy. I don't believe that Pluto will be dropped from our planet repertoire, but this "tenth planet" discovery will certainly require international debate and a new definition of what will define a planet.

On August 2nd, 2005 Robert Roy Britt [] wrote:

The claim Friday that a 10th planet has been discovered in our solar system has set off a fresh round of debate and international talks aimed at defining the most vexing term in astronomy: the word planet.

A formal proposal could come within a week or two. But some astronomers see no easy resolution.

Now, the guy who stirred the latest dust is trying to snuff the whole debate by repositioning planet as a cultural term that no longer has any scientific meaning.

"Scientists have for the most part not yet realized that the term planet no longer belongs to them," says Caltech's Mike Brown, who led the discovery of the new larger-than-Pluto object.

Brown's new view comes after contemplating six years of mostly fruitless scientific arguments that began when the public became outraged over a rumor that scientists planned to demote Pluto, a rumor rooted in the fact that some astronomers had already stopped calling Pluto a planet by the late 1990s.

"I finally realized the mistake we astronomers had been making all along," Brown told yesterday. "The word planet is simply not a scientific word, it is a cultural word. Once you get over that trap the rest becomes easy."

The problem

At the heart of the problem is small world that should never have been called the ninth planet when it was found 75 years ago.

Pluto is small, its orbit very noncircular, and it travels 17 degrees outside the main plane of the solar system where the other planets roam. In recent years, several other round worlds at least half as big as Pluto have been found on similar offbeat paths, including two announced last week in addition to 2003 UB313, whose orbit is inclined a whopping 45 degrees.

Most astronomers view all of them, Pluto included, as members of the Kuiper Belt (other terms are used, too, to describe the increasingly complex outer solar system).

The newfound object, temporarily named 2003 UB313, is perhaps 1.5 times the diameter of Pluto and appears to have a similar surface rich in frozen methane. So Brown called it the 10th planet in a hastily arranged teleconference with reporters Friday evening.

NASA, which funded the research, appeared to endorse the label by using Brown's terminology in its official press release.

But yesterday, NASA's Paul Hertz said, "It's not NASA's job to decide what is and what is not a planet." Hertz, chief scientist in the agency's Science Mission Directorate, acknowledged the task falls to the International Astronomical Union (IAU).

"We anticipated there would be a difference of opinions," Hertz said in a telephone interview.

Wildly different, it turns out.

If 2003 UB313 is a planet, one argument goes, then so are those other round things out there. So the new kid on the block would have to go to the back of the line, numerically. It might be No. 12 or No. 24, depending on whose scheme you like.

Proposal soon?

Efforts to craft an official definition have dragged on for years.

The IAU, responsible for nomenclature of all things beyond Earth, has been mulling a planet definition since at least 1999. An IAU Working Group specifically set up to develop a recommendation has been stalled for the past six months.

But most of the dozen members in the group were "exchanging a lot of email this weekend," said Alan Stern of the Southwest Research Institute, who is on the committee.

The members have said they "want to get something done, pronto," Stern told He said it's possible a proposal could be finalized in a week or two and made public. Still, group members have clearly different ideas in mind.

A synopsis of Stern's thinking:

A planet is a body that directly orbits a star, is large enough to be round because of self gravity, and is not so large that it triggers nuclear fusion in its interior.

"I think there's a consensus moving in this direction," Stern said.

The actual definition will, at least, be more complex than that. Stern favors calling the smaller objects dwarf planets, for example. Other astronomers prefer the term minor planet. Another term bandied about is Kuiper Belt planets. Some don't like the idea of applying the planet label at all.

Let there be 8

Brian Marsden, who is also on the IAU Working Group and who runs the Minor Planet Center where data on objects like these end up, says a simple definition like Stern's makes sense from a theoretical point of view.

If adopted, the wording would bring our solar system's tally of known planets to about two dozen, Marsden said.
A Revolution

A swarm of small worlds discovered in recent years is remaking our view of the solar system, astronomers agree. Pluto, once an oddball, is now thought to be one of many round objects out there.

"It's really a revolution," says Alan Stern of the Southwest Research Institute. "We are finding out just how quaint our view of the solar system was."

Improved technology promises more discoveries. Some astronomers won't be surprised if something as big as Mars, or even Earth, is found way out there but still bound to the Sun. So far, only a fraction of objects thought to be in the Kuiper Belt, beyond Neptune, have been found.

Stern, who is managing NASA's New Horizon's mission to Pluto, points out that there is a billion times more space in our solar system beyond the Kuiper Belt compared to inside that region.

"Hold onto your hat," he said. "It's just going to get more bizarre."

But practically speaking, Marsden, who expects it will take "somewhat more than a week or two to come up with a policy," prefers another approach.

"The only sensible solution is to accept that the solar system contains the eight planets known a century or so ago," Marsden said via email, "and to add new members only if they are larger than, say, Mars -- or maybe even the Earth."

(Stern and others contend that such large worlds indeed await discovery.)

The discovery of 2003 UB313 presents "the best chance to resolve the problem," Marsden said. "I doubt that all astronomers will be happy with the outcome, but I would hope that what is decided is enough of a compromise that most of them are."

Forget science

Mike Brown yesterday attempted to shift the whole debate away from science.

In Brown's mind -- and he admits to changing it recently -- Pluto is too enshrined in our culture, from place mats to postage stamps, to strip it of planethood.

"Some astronomers have rather desperately attempted to concoct solutions which keep Pluto a planet, but none of these are at all satisfactory, as they also require calling dozens of other objects planets," Brown wrote on his web site this week. "While people are perhaps prepared to go from nine to 10 planets when something previously unknown is discovered, it seems unlikely that many people would be happy if astronomers suddenly said, 'we just decided, in fact, that there are 23 planets, and we decided to let you know right now.'"

Brown's team is taking a stand.

"We declare that the new object, with a size larger than Pluto, is indeed a planet," Brown wrote. "A cultural planet, a historical planet. I will not argue that it is a scientific planet, because there is no good scientific definition which fits our solar system and our culture, and I have decided to let culture win this one."

He advises the public to "ignore the distracting debates" of the scientists.

It seems clear the IAU Working Group plans to ignore Brown, at least insofar as they expect to forge a scientific definition.

Yet no matter what the group comes up with, you can bank on at least one more year of debate. For a definition to be made official, it must be voted on at an IAU General Assembly meeting. The next one is in Prague in August, 2006.

I say...leave the name and retain Pluto as part of popular lore of the solar system...the scientists can provide the proper nomenclature for their purposes.

A Double Planet?: Pluto and Charon


Isaac Asimov, Frank Reddy , and Greg Walz-Chojnacki

ISBN: 0836812328

Beyond Pluto


John Davies

ISBN: 0521800196

Clyde Tombaugh: Discoverer of Planet Pluto


David H. Levy

ISBN: 0816513171

How Did We Find Out About Pluto?


Isaac Asimov and Erika Kors [illustrator]

ISBN: 0802769926

Ice Worlds on the Ragged Edge of the Solar System


Alan Stern and Jacqueline Mitton

ISBN 3-527-40556-9

Out of the Darkness the Planet Pluto


Clyde William Tombaugh and P. Moore

ISBN: 0451619978



Carmen Bredeson

ISBN: 0531117847



Larry Dane Brimner

ISBN: 0516264990



Steve Potts

ISBN: 1583401016



Dana Meachen Rau

ISBN: 0756502977



Gregory Vogt

ISBN: 1562943936

Pluto and Charon : Ice Worlds on the Ragged Edge of the Solar System


Alan Stern and Jacqueline Mitton

ISBN: 0471152978

Pluto and Charon


Alan Stern, David J. Tholen and S. Alan Stern [editors]

ISBN: 0816518408

Pluto: The Ninth Planet


Michael D. Cole

ISBN: 0766019535

Uranus, Neptune, and Pluto


Tim Goss

ISBN: 1588109186

New Horizons

Onboard name identified by #397611

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