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My New Book on Pluto

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Showing 1-12 of 12 posts in this discussion
Initial post: Jul 28, 2010 6:34:30 PM PDT
I'm a writer, amateur astronomer and astronomy graduate student, and I am writing a book about Pluto, specifically focusing on why it should keep its planet status, worldwide efforts to this end, and the remarkable resilience of a little planet that continues to generate big debate. The tentative title is "The Little Planet that Would Not Die: Pluto's Story." I hope to complete it by the end of the year. For a preview, visit my Pluto Blog at
Your reply to Laurel E. Kornfeld's post:
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Posted on Sep 6, 2010 8:53:12 AM PDT
Paul123 says:
If your looking for a reason how about I met Clyde Tombaugh and JW Christy.

In reply to an earlier post on Sep 6, 2010 10:05:48 AM PDT
I would like to hear more about this. Are you an astronomer? In what context did you meet them? Please email me at Thanks.

In reply to an earlier post on Sep 7, 2010 7:33:10 AM PDT
Last edited by the author on Sep 7, 2010 7:34:18 AM PDT
Paul123 says:

I am a amateur astronomer. I met them at the Riverside Telescope Makers Memorial Weekend gathering. I do not remember the date but it probably was in the late 1980s or early 1990s. I was only one of many who lined up to get a signature. I have a poster with signatures of the two men and thier wives Patricia Tombaugh and Cher Christy on my wall. I remember the spouses being very surprised I would want their signatures. I normally would not have had it framed and mounted but I also took a picture of my two children next to Mr Tombaugh while he was signing. Their picture was include in the framed poster.

I have just noticed the poster has a date of 1989, given my childrens apparent ages that seems about correct.

Best wishes on your book.

In reply to an earlier post on Sep 16, 2010 8:46:38 PM PDT
Hi Laurel,

We have a chapter about Pluto losing it's planethood in our new book:
The 50 Most Extreme Places in Our Solar System

More details a

In reply to an earlier post on Sep 16, 2010 9:48:26 PM PDT
Thanks for sharing the story. You are so lucky to have met Clyde. I met his daughter, son-in-law, and great grandson at the Great Planet Debate at the Johns Hopkins University Applied Physics Lab in Laurel, MD in August 2008. My astronomy club has an autographed photo of him on our wall which a member obtained in the late '80s when he met Tombaugh at Stellafane. I sincerely hope Patsy Tombaugh gets her wish to be around for the New Horizons flyby!

In reply to an earlier post on Sep 16, 2010 9:50:20 PM PDT
Could you please present both sides of this ongoing debate rather than say it's a done deal just because four percent of the IAU voted? If it's possible to make revisions, it would be a great service to the public to let people know that this demotion remains controversial and is not accepted by many astronomers, including the Principal Investigator of NASA's New Horizons mission to Pluto, Dr. Alan Stern, and 300 professional astronomers who signed his petition rejecting the demotion.

Posted on Sep 21, 2010 10:38:14 AM PDT

Most of what I have seen on the 'pro' side of the argument has taken the form of emotional arguments from tradition backed by ad hoc reasoning. Your phrasing suggests the same: "on why it should keep its planet status" should read *regain* in place of *keep*. Also, your use of "demotion" instead of a less pejoritive term like "reclassification".

The idea of a public petition having any weight on astronomers is inherently flawed - why should astronomers allow the laity to define their technical language for them? This precedent might be very helpful for anatomy students, but is a dangerous idea if extended to more controversial subjects such as evolution where non-scientists already abuse scientific language.

But I do love astronomy so if you could point me to some critical sources that argue in favor of Pluto's planet status, I'd enjoy reading them. And I will still look forward to reading your book, whether I agree or not :)

Posted on Sep 21, 2010 3:27:35 PM PDT

At the center of the argument made by the Pluto is not a planet side is the claim that opposition to the change in Pluto's status is largely emotional. This is not true; it is used as a means to discredit the pro-Pluto as a planet position. While many individuals on both sides might be motivated by emotional concerns, the reality is there is a strong scientific case for not just Pluto but all dwarf planets to be considered a subclass of planets.

In fact, one could argue that a principal argument made by supporters of the IAU decision, that "we cannot have too many planets" and must limit the number of planets in the solar system could itself be considered based on emotion. The solar system has the number of planets it has, regardless of convenience or ease of memorization.

The term "dwarf planet" was coined by New Horizons Principal Investigator Dr. Alan Stern to indicate a third class of planets in addition to terrestrials and jovians--planets big enough to be rounded by their own gravity, a state known as hydrostatic equilibrium, but not big enough to gravitationally dominate their orbits. Stern never meant for dwarf planets to not be considered planets at all. In astronomy, dwarf stars are a subclass of stars, and dwarf galaxies are a subclass of galaxies, so it only makes sense that dwarf planets should be a subclass of planets. Yet four percent of the IAU voted otherwise.

I, in conjunction with many planetary scientists who opposed the IAU decision, believe we should be broadening rather than narrowing our conception of planet as we discover more and a greater variety of planets in this and other solar system. The planet definition I favor is based on geophysics. Specifically, a planet is a non-self-luminous spheroidal body orbiting a star. If an object has enough mass to be shaped by its gravity rather than by chemical bonds, the way asteroids are, it is a planet. This is very much in conjunction with the definition of star, which is also based on mass--specifically, a star is self-luminous because it is massive enough to initiate hydrogen fusion.

Just because Pluto is different from terrestrials and jovians doesn't make it a non-planet. It makes it a different kind of planet. With a broad definition, we can distinguish types of planets through use of subcategories, the same way we do with stars using the Herzsprung-Russell Diagram.

A major problem with the IAU decision is that it relies solely on dynamics; that is, it classifies objects by where they are while ignoring what they are. This results in the absurdity where there could be two identical objects, one of which is considered a planet and one of which is not. If Earth were in Pluto's orbit, it would not be considered a planet either. A definition in which the same object can be a planet in one location and not a planet in another location makes little sense.

I deliberately choose to use the wording "keep its planet status" rather than "regain" because I believe Pluto and all dwarf planets never stopped being planets. Just because four percent of the IAU issued a decree doesn't change reality. As for the term "demotion," it has been widely used and makes sense because the decision put Pluto in a lesser category than the planets--though "reclassification" is just as fine with me.

The public petition is being done in support of a petition by 300 professional astronomers led by Stern rejecting the IAU decision. You can find that petition here: . The fact is, the IAU decision was made under questionable circumstances by only 424 out of 10,000 members, most of whom are not planetary scientists. Many planetary scientists are not members of the IAU and have no say in this at all. Also, the IAU was formally asked by professional astronomers to reopen the debate at its 2009 General Assembly and refused, leading a large group of planetary scientists to boycott the conference. The point is, many astronomers were also excluded from this decision, and many objected to it only to be ignored.

I do believe there is a role for amateur astronomers and the public in this matter, especially considering the division among professional astronomers and the broad implications for teaching and education. Teaching that Pluto or any object is no longer a planet just because a certain authoritative body decreed so equates to dogma rather than science. Teaching the controversy, giving credence to both sides and asking children and adult students to think about these issues and come to their own conclusions is what science is about.

Here are some sources that make cases for Pluto's planet status. The Great Planet Debate, held at the Johns Hopkins University Applied Physics Lab in August 2008, involved astronomers presenting both sides of the issue. Audio transcripts are available at . Some good books are "Is Pluto A Planet?" by Dr. David Weintraub; "The Case for Pluto" by Alan Boyle; and "Pluto Confidential," by Laurence A. Marschall and Stephen P. Maran, two authors, one of which favors the IAU decision and the other who opposes it. "Ten Worlds," a hard-cover book appropriate for children and adults by Dr. Ken Croswell, is another good source, as is Croswell's interview here: . There is also my blog, , which intersperses arguments in favor of Pluto's--and all dwarf planets' planet status with chronicles of worldwide efforts opposing the IAU decision.

Hope these help, and thank you for your interest in my book!

Posted on Sep 22, 2010 6:04:04 AM PDT
Wow, thank you for taking the time to write a very detailed response. Good details and good resources :)

Posted on Jan 10, 2011 3:24:26 PM PST
I just happened upon these posts. I am an on again off again amateur (fair weather, I have cancer). I am not familiar with all of the names etc. connected with this issue.
I have only one question. It has always been my understanding that the original reason for the search for Pluto was it's gravitational effect on Neptune. (Maybe I'm just old)
I would think this alone separates it from being just a rock which hasen't a cleared it's orbit!

In reply to an earlier post on Jan 10, 2011 10:02:06 PM PST
First, I'm so sorry to hear about your condition and sending you best wishes for a complete and speedy recovery.

Your question touches upon a section of the book I was just working on today! Yes, the original search for Pluto was because of suspected perturbations of the orbits of both Uranus and Neptune. Neptune was searched for and found because Uranus' observed orbit did not match its calculated orbit, and astronomers believed this was due to the influence of yet another planet. Because this was the case with Neptune, there was the assumption that the same thing applied regarding the influence of yet another planet. It turns out that there were no discrepancies in Neptune's orbit, but this was not known until the 1980s Voyager II flybys. The "discrepancies" were solely due to human error. However, this does not mean Pluto is just a rock. Pluto is large enough to be pulled into a round shape by its own gravity, a characteristic of planets known as hydrostatic equilibrium. The requirement that an object must "clear its orbit" to be a planet is controversial and not accepted by many astronomers. It is inherently biased against planets further from their parent stars, which have a larger orbit to clear, and leads to the absurdity in which the same object (such as Earth) can be a planet in one location and not a planet in another. If Earth were in Pluto's orbit, it would not clear that orbit either. You can find out more from my Pluto Blog at
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Discussion in:  Astronomy forum
Participants:  5
Total posts:  12
Initial post:  Jul 28, 2010
Latest post:  Jan 10, 2011

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