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Celebrating Pluto [Feb. 18th, 2009|02:03 pm]

Today is the 79th anniversary of the discovery of planet Pluto by 24-year-old Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. The observatory is celebrating that milestone, "Pluto Night," tonight with presentations by astronomer and New Horizons team member Will Grundy and by Outreach Manager Kevin Schindler, who will share the exciting story of Pluto’s discovery and astronomers’ current efforts in trying to understand Pluto and its neighbors. Visitors will also have an opportunity to check out the Orion Nebula and other fascinating objects through their telescopes. More on this event can be found at http://www.lowell.edu/outreach/events.php . This is one event I deeply regret missing, but Flagstaff is a long way from New Jersey. Still, I do plan to make a visit to the Lowell Observatory one of the goals I hope to someday accomplish.

Interestingly, the anniversary of Pluto's discovery is being noted around the world by many articles, blog posts, and events, once again illustrating the compelling draw of this tiny body of which the world cannot seem to get enough.
Several weeks ago, I noted the dedication of Tombaugh's 16-inch telescope at Rancho Hidalgo in New Mexico. Pictures from the dedication ceremony can be viewed at

How notable is it that fully two and a half years after the IAU--or, rather, four percent of the IAU--thought they had settled this issue for good, that it becomes more and more evident every day that the issue is not settled. Why should it be? Why should the world settle for a sloppy definition adopted in haste by astronomers more eager to get home after a two-week conference than to deliberate sufficiently so as to arrive at a thoughtful compromise? In the March 2009 issue of Sky and Telescope, Dr. David Grinspoon argues rightly that the world should not be forced to accept a flawed planet definition. His article and an 11-minute podcast on why the planet definition issue needs revisiting can be found here:

Also fascinating to me is the reference to this blog in several blog posts by various astronomers and astronomy journalists. It seems the backlash against the IAU decision is gaining momentum. On four separate occasions in just the last few weeks, this blog was discussed in relation to the Pluto debate. These references can be found at the following sites:

http://philosophyofscienceportal.blogspot.com "Pluto: A Reader's Contribution" 2/5/09
http://astroprofspage.com/archives/1898 "Defining Planets" (Part 1) 2/2/09
http://physics.about.com/b/2009/01/31/the-other-side-of-pluto.htm "The Other Side of Pluto" 1/31/09
http://tierneylab.blogs.nytimes.com/2009/01/10/how-many-planets-do-you-want-in-the-solar-s ystem/ "How Many Planets Do You Want in the Solar System?" 1/10/09

he Internet has provided people the world over an opportunity to make a difference, to influence this debate in a way we never could have in its absence. In the pre-Internet world, four percent of the IAU would have voted, and that would have been the end. Many people, both scientists and lay people, would still have been unhappy with the flawed decision, but we would have had limited venues with which to express our views. Supporters of the demotion, especially if they are professionals with PhDs, would get the media attention, the op-eds and the interviews, and in spite of the definition's many deficiencies, there would have been precious little the rest of us could do to fight this. Thankfully, today, we have this venue that democratizes this debate, allowing all to have an equal say in this matter and, most importantly, allowing Pluto supporters to counter the claims of those who support demotion that our views are based solely on sentiment. They are not. There is strong scientific reasoning for the continuing classification of Pluto as a planet.

Here is one of the most compelling arguments yet.  A newfound pair of exoplanets has been discovered, which has the same 3:2 orbital resonance as Neptune and Pluto. The two planets revolve around an orange dwarf star named HD 45364 in the constellation of Canis Major, about 110 light years from Earth.  The inner planet completes three orbits around its star in the same time it takes the outer planet to complete two orbits. Therefore, the inner planet at times lies further from the star than the outer planet--just like Neptune and Pluto. For 20 years of its 248-year orbit, Pluto comes closer to the sun than does Neptune. Both of these exoplanets have elliptical orbits.

Both of these are giant planets; the inner one is at least 3.5 times the mass of Neptune. Its average distance from its star is approximately that of Venus from our sun. The outer planet is more massive, at least 2.2 times the mass of Saturn. It is slightly closer to its star than the Earth is to the sun.

According to the IAU definition, neither of these objects would be considered planets, as they do not "clear their orbits" of one another. According to Dr. Neil deGrasse Tyson, crossing another planet's orbit is "no way for a planet to behave." What, then, are these giant objects? Are they really not planets, or more likely, did some astronomers hastily adopt a planet definition based on arbitrary constrictions? More about this planetary system can be found at

Another exoplanet discovery illustrates that having an orbit that is "comet-like" does not make an object a comet. A large exoplanet, HD 80606b, four times the size of Jupiter, circles its star in only a few days in a comet-like orbit. Is this object, which is bigger than any in our solar system, not a planet but a comet because of its highly elliptical orbit?

More information on this exoplanet can be found at http://www.centauri-dreams.org/?p=5767

The conclusion is clear. Unless astronomers want to blatantly exclude these giant objects from planet status, they have to recognize that an  object not clearing its orbit, crossing the orbit of another planet, and/or having a comet-like orbit do not in fact disqualify celestial objects from consideration as planets. And it may be just a hunch, but personally, I have a feeling that we are going to see more, not fewer, strange exoplanet discoveries that only confirm the ridiculousness of the IAU's 2006 planet definition.

Another interesting tidbit that further discredits Tyson's claim that affinity for Pluto is limited to the US is that just yesterday, I received a message from an astronomy journalist in Argentina stating his support for Pluto's planet status. People around the world are speaking, and they are celebrating planet Pluto. Forget the silly 1930-2006 line that has graced some blogs and T-shirts. It's 2009, and planet Pluto has not gone anywhere. The debate will not end with a nonsensical definition best described in Jonathan Coulton's song, "I'm Your Moon," as "they invented a reason."

For those further interested in Pluto's fate, Dr. Alan Stern will be at the American Museum of Natural History in New York on Tuesday, March 10 at 7:30 PM for the 2009 Isaac Asimov Memorial Debate, which will focus on Pluto. Dr. Tyson will act as moderator. Tickets are $18 and should be purchased in advance. More information can be found at
http://www.amnh.org/programs/programs.php?event_type_id=3&bytype=1 . I hope to be there and to meet other Pluto supporters there.

On the next night, Wednesday, March 11, NASA Solar System Ambassador Dr. Ken Kremer, a friend of mine, will discuss Pluto and the New Horizons Mission at the Rittenhouse Astronomical Society at the Franklin Institute Science Museum in Philadelphia from 8-9:30 PM. He will join Dr. Max Mutchler of the Space Telescope Science Institute, who discovered Pluto's two tiny moons Nix and Hydra.  Mutchler will begin the evening program at 7:30 PM. More information can be found at

Meanwhile, all the discussion resulting from Tyson's book has inspired me with the goal of writing a book about Pluto as well, one that will address both the scientific issues surrounding the debate and the cultural aspect of Pluto and worldwide support for its planet status--all from the viewpoint of an unabashed Plutophile. This project is still in the research state, so it's going to be a while before it becomes reality. However, I'm pretty sure the Pluto debate will continue for quite some time, creating a fertile climate for books and articles on this subject. I agree with Tyson, who responded to my project with "the more, the merrier." Of course, I better get it done well before 2015, or New Horizons data will make most of the information obsolete!

Happy Discovery Day, Pluto (not birthday, as Pluto was here long before we found it!)! This year, your planetary status is still a matter of debate. Next year, may it be a fact officially recognized worldwide.

[User Picture]From: polaris93
2009-02-19 04:21 am (UTC)
As always, your posts on Pluto are a delight to read, and provide plenty of ammunition with which to fire back at those who want to classify the KBOs as "dwarves." (BTW, Astronomer Bill Napier has pointed out that the Oort Cloud probably contains a wealth of Earth-sized objects and even larger ones, possibly up to gas giants. What would Bill Brown & Co. do about those, one wonders?) Let us know when your book comes out -- I'd love to have a copy. :-)
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From: sowff
2009-02-27 11:08 pm (UTC)

Happy Birthday, Pluto!

Hi Laurel,

Wow, thanks for reminding me!

Let's hope Alan insprires the replanethood of Pluto in Rio this summer!

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From: ext_172349
2009-03-05 04:30 am (UTC)

Discovery Discovered

Hey... Good Morning! Thanx for dropping by my blog and sharing your knowledge. You have a nice blog with all great info.
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[User Picture]From: laurele
2009-03-05 05:25 am (UTC)

Re: Discovery Discovered

Thanks for taking the time to read my blog! Your blog is equally informative. I just wanted to provide another perspective on the Pluto issue.
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From: (Anonymous)
2009-03-05 07:11 pm (UTC)
The argument for Pluto's planethood is even stronger than stated here. In the article by Ken Croswell, he notes that HD 45364 is not unique. Two other stars--HD 82943 and HD 128311--also have planets whose orbits overlap, so that the inner and outer planets flip positions.

Think about that. There are roughly 300 extrasolar planetary systems known. We currently know of three whose orbits at least touch. That's 1 percent of the total.

Now think about all the extrasolar planets that we DON'T know about--smaller, Earth-sized planets that may cross the orbits of the giant planets we DO know about. Are we not going to call Earth-sized planets planets simply because they commit Pluto's "sin" of crossing another planet's orbit?
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[User Picture]From: laurele
2009-03-05 11:54 pm (UTC)
Thank you for this very noteworthy information! I have always believed that once we find the tremendous variety of exoplanets out there, many of which don't, in Neil deGrasse Tyson's words "behave like a planet should," astronomers will completely rethink the concept of planet and will broaden rather than narrow it to fit the many amazing new finds. We know of only one complete sample of a solar system, and that is our own. Hopefully, once we see more whole solar systems, we will be more open toward the "infinite diversity in infinite combinations" out there.
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