I love your site. They really look very nice. The articles provided are long enough to provide great content but not so long as to be totally engrossing, if you know what I mean….

Interesting post. I came across this blog by accident, but it was a good accident. I have now bookmarked your blog for future use. Best wishes. Ragheb Alama Website Team.

Mr. Robert Roy Britt in this drippingly sarcastic comment has identified his own intellectual failing - he has elevated science and his own opinion to religious status. Science often doubles back upon itself when the scientific community identifies a mistake or redefines an issue, so it reveals its infinite fallibility, so why why should we now by Britt’s implications in this comment, become dogmatic on an issue not universally agreed upon by the scientific community? On his opinion alone?

Speaking as a Sceince teacher who also holds a degree in theology I would say that Britt combines the self-righteouness of a bad theologian and the opininated arrogance of a bad scienctist. Public opinion and the scientific communities opinions do not count for defining truth, but they also do not count for nothing.

In another field of science, nutrition and health, the RIGHT answer to health concerns are redefined at a blinding pace - so Britt’s esteemed insights may be as scientifically passe as Pluto in a very short time. There are “eternal truths” in religion, not in science Mr. Britt, so it is time to get off the oracles throne and get back to the telescope.

As far as these factors go I would imagine that there would be a distinction between planets that have atmospheres and those that don’t. (And maybe those that do during certain parts of their orbital cycle.) The second factor would be the mass of the object.
The third being the orbital eccentricity of the object.
The last being the angle of the normal of the objects orbital plane and the orbital planes of the innermost planets.

These four criteria should provide enough distinction between other objects and planets, but again who really cares. And if you care is it more of an emotional thing or is there intellectual weight to this? Maybe I am not seeing the bigger picture?!?

OK, I’m loathe to wade into this debate (and to be fair, I work in extragalactic rather than solar system astronomy) but I disagree that this needs to be a matter exclusively for the IAU. The IAU have announced that they will define “planet” in September 2006, but in my opinion this is a question of semantics rather than science. Science is no more equipped to answer this question than it is to define a continent (look up “continent” on wikipedia) and the reason why the IAU is having such difficulty over this is that scientists are no better equipped to deal with purely semantic questions than the public at large. Does a planet need to be round, does it need to be one of the “historical nine planets”, or should we rely on the original definition of the word, “a wanderer” (by which definition the Earth is not a planet!)?

Consider the electromagnetic spectrum. Sometimes X-rays can be higher frequency than gamma rays, depending on whether the source is nuclear or electronic. The divisions between microwaves, infrared and radio are also somewhat arbitrary. Some professional body or other could decide exactly where the boundaries of “visible light” are. But if your eyes can see a little further into the so-called ultraviolet than mine, does this pose a crisis for science? No.

I’m happy for the IAU to decide, but whatever they decide, I’m happy for you to call Xena whatever you like, the same as I’m happy for you to call M31 the Andromeda Galaxy, NGC 224, 2MASX J00424433+4116074, Fred’s Pet Galaxy Number 70, or whatever. The IAU might frown on the latter, but really, go ahead, call it what you like. My preference is to go with the historical definition (we don’t add or subtract objects from the Messier catalog), but I can understand the opposing viewpoint. When you say “Messier object”, folks know what you’re talking about (well, astronomers, at least); but the definition of a planet, being a word that is used in the common parlance, is, if you’ll forgive the pun, a little messier.

As for fear of rewriting textbooks, that is what science is all about. When Hubble discovered that the “spiral nebulae” were in fact external galaxies I’m sure this prompted a few textbook rewrites. Would someone like to tell me where the dividing line is between a galaxy group and a galaxy cluster? Undoubtedly some of you would, but there will be disagreement over where the line falls. The galaxies themselves don’t care; some of them are isolated, some have companions or are in groups, clusters of various Abell classes, superclusters, filaments and sheets in the Large Scale Structure …

Let’s just agree that “planet” can be defined in a number of different ways depending on whether you’re more concerned about history or morphology. As for how they form, what their composition is, how they evolve, and whether or not they may harbor life … for me, those are more interesting questions for science to answer.