Is Pluto A Planet?

damiangerous writes: "This NY Times story reports the controversial decision by the American Museum of Natural History to no longer list Pluto among the planets. Although they don't actually declare Pluto's loss of planetary status outright, their newly opened planetarium classifies Pluto simply as a Kuiper Belt object. A staff member says only 1 in 10 people ask about the 'missing' planet."

Comments

Jupiter

[boarder]

Jupiter is, IIRC, 10 times smaller than the smallest classifiable star. Pluto is just barely on the borderline of planet and planetoid (it is almost HALF the size of the moon and over HALF the size of Mercury). Jupiter is much farther from being a star than Pluto from being a planet. If Pluto is not considered a planet, there is NO WAY Jupiter will be considered a "failed star."

Pluto also doesn't orbit like a normal planet. Most planets have near circular orbits; besides Pluto, the greatest eccentricity of the planets in our Solar system is 0.20563 (Mercury) and the rest are on the order of 0.04. Pluto has an eccentricity of 0.2444. That isn't much of an argument, but if you look at the fact that the inclination of its orbit is 17 degrees while the rest are around 1 or 2 degrees (Mercury is 7 degrees) it doesn't orbit like a planet but more like a captured object.

In the past I have defended Pluto being a planet; but, after looking at what else is out there of around the size of Pluto and comparing them to other planets, I'm not so sure. In my opinion, though, it is almost a moot point. We know it is there, what it is made of and a lot more about it; I personally don't care how it is classified (that is only a point for astronomers and exogeologists to quibble over).

To get back to Jupiter, though, I think it was also formed much differently than a star. I don't know if formation is part of the classification of astronomical objects, but if it is then Jupiter still wouldn't be a star even if it were larger. The planets we've found orbiting other stars have all been of around Jupiter's size, but some were over twice as large and they are still planets.

Sadly, the Hayden is riddled with errors

[pq]

Reading this NYT article actually made me chuckle - I visited the Hayden on Jan 2nd, and in two hours of casual exploration, I found the place riddled with errors. Scary!

For example, there's a quasar image, labelled as an image of the Cartwheel galaxy; sure enough, some distance away is the true Cartwheel galaxy, and no, its not labelled as a quasar, its labelled correctly. Huh? Labels are rampantly swapped in their example of objects at various wavelengths: as an astronomy grad student, I know what the Orion nebula looks like, and boy, it looks different from the Sun - its almost like someone dropped all the captions, then picked them up and stuck them back on at random. And finally, the labels for elliptical and spiral galaxies are swapped. I kid you not!

And this was a cursory walkthrough, not a very detailed examination - things are just plain wrong! I was planning to write a note to the director, but I'm not so sure its a good idea... Apparently they spent all their money on the (extremely beautiful!) building, and had no money left to hire a couple of trained monkeys (grad students) to do some fact checking.

Re:Not a good precident to set

[hubie]

I am not saying that one should not question scientific authority. I am saying that it is not the museum's place to re-interpret scientific authority. My position is probably best summed up in the AC reply (#11) to my comment that the museum has sided with the minority view on this issue that the museum does a disservice to the public by not presenting Pluto's place as defined by the IAU. There are many scientists that view Jupiter as a star that didn't have enough mass to initiate fusion; does this mean that the museum should remove Jupiter from the Planet classification and put it under a separate title such as Protostar? You can find people that advocate this, but I doubt many would change their view of Jupiter.

Take another example: the face on Mars. There are people who are strong advocates of this, some who are technically-trained and have Ph.Ds. I don't think it is the place of the museum to make a whole extra exhibit on the Face within the context that the scientific community is undecided on this issue (on the other hand I think it would be in their place to present this in the context of mankind's romantic ideas of Mars, including such things as Percival Lowell's canal observations). It is the place of the scientists and citizens who advocate the Face to question the authority and make their case; it isn't the museum's place to do that for them.

I also do not advocate censoring museums, but I do think that museums have a responsibility to present information accurately and within historical context, especially the American Museum of Natural History. I think that by selectively removing Pluto as being listed as a planet when the IAU classifies it as a planet is being inaccurate. Because this was a deliberated decision of omission, it does make one wonder what other museum exhibits are subject to their reinterpretation/selected-omissions.

Not a good precident to set

[hubie]

I think the museum is incorrect in their position by going against the stance of the international community. The museum seems to argue that the status of Pluto is a controversial open question and they are taking what they feel is the correct side of the "controversy" (they argure that they sidestep the controversy, but in doing so they are in fact taking the side opposite the predominant scientific opinion). However, as far as the international astronomical community is concerned, there is no controversy.

If the museum wants to take this approach, they may as well include other significant sections to the museum, such as a phrenology section when discussing current medical and psychological techniques. There are some people who still advocate phrenology, so therefore it must be a controversial subject and they should present all sides of this issue. This kind of handling of issues is just a reflection of what passes as journalism these days: no matter what issue is being presented, give equal time to an opposite opinion no matter how insignificant this opinion is considered because this is supposed to show "balanced" and "un-biased" reporting. What it does in many cases is promote very minor opinions and give them legimate status and create controversies that do not really exist.

To present something within historical context is one thing, but an exhibit on the current state of things should reflect the current majority opinion. It might turn out that down the road the international community changes its mind about Pluto, but until then the museum should list it as one of the planets.

Re:We need a simple definition of planet...

[WolfWithoutAClause]

I think that the fact that the center of mass of the earth-moon system is within the earth's surface disqualifies the moon from being a planet.
Hence it is the earth's moon, not the Sun's planet.

The moon is big enough and ugly enough to be a planet, but it needs to leave the coat tails of it mommy to count as a grownup around this solar system. Check out Space 1999 for tips on how to arrange for this. ;-)

Splitting fine hairs

[Big Torque]

As I can see it the only things going against Pluto being a planet is the fact it is small, and the fact it is not in the same plane of orbit as the other so called planets. That's about it. Apparently there has been a group of folks who thinks if it did not form out of the original disks of material around our sun it is not a planet. Whatever. Pluto is orbiting around the sun not another planet. It itself has a moon. Pluto and its moon seem to be round and not just two big rocks. The fact is we have not sent anything to Pluto. All we know about it is that it is a fuzzy ball with another fuzzy ball around it very fare away from the sun. and that it has a non standard orbit for a planet. That is about it folks! In the end this has all been an act to force one narrow idea of what a planet is and it not. In the end that is what it comes to. I fear that it will make it harder to finally send a something to Pluto if it is not seen as a planet. This would be a shame.

While they're at it...

[Sandlund]

...why don't they just list Jupiter as a failed star?

Pluto's moon is NOT round...

[TWX_the_Linux_Zealot]

I have a friend who works at the Arizona State University geology department, Planetary Sciences, Space Photography Labratory, named Dr. David Williams (who by the way is an avid Star Trek Fan, but that's beside the point). A club that I'm in was given a tour by him of the lab, and I asked him about pluto, and he said something to the effect that Pluto's moon is NOT ROUND. Most of the tour was spent on Mars stuff, so I didn't think of getting into details, but I'm fairly confident that I am remembering properly that he said that Pluto's moon is not round...

"Titanic was 3hr and 17min long. They could have lost 3hr and 17min from that."

We need a simple definition of planet...

[Throw Away Account]

I really think that the basic problem is the lack of a simple definition of planet. I'd suggest that the definition have two components, and two alone:

1) Sufficient mass/gravity to form itself into a sphere (centrifugal force and tidal effects excepted).

2) An entirely concave orbit around a star.

Now, this would add one new planet to the current nine -- Earth's Moon. Other than those ten objects and the Sun, all are either irregular in shape and/or in planetary orbits that cause their solar orbit to be convex.

Re:We need a simple definition of planet...

[Throw Away Account]

1) Yes, it's a bit fuzzy where spheres become non-spheres.

2) Every object in the solar system does orbit the Sun, either on its own or as a consequence of its orbit around another body. Given that every one of those orbits are peturbed by other objects in the solar system, how do we distinguish which are in orbit around the Sun and which are in orbit around another body in the solar system?

You seem to suggest looking at the center of gravity of two objects in roughly the same solar orbit. In that case, Pluto is certainly not a planet, since the barycenter (center of gravity) of Pluto-Charon is outside of Pluto. More importantly, it leaves the degree of difference between two solar orbits for such classification undefined -- without such a definition, one could argue that there are no planets, since the center of gravity of (say) Neptune and Jupiter is outside of both bodies.

I suggest instead that we look at the nature of each object's orbit around the Sun. Of the spherical bodies in the solar system, ten have orbits that are always concave to the Sun (always convex in terms of geometric shape) -- the nine recognized planets and the Moon. Charon and many asteroids, comets, and other planetessimals also have such an orbit, but such objects are obviously irregularly-shaped.

The point is that the Moon is not clearly in orbit around the Earth -- it has a mutually perturbing joint orbit with the Earth around the Sun, instead.

Re:We need a simple definition of planet...

[Throw Away Account]

The nine recognized planets, the Moon, Charon, and a wide variety of planetessimals are in orbits that can be described as concave to the Sun or convex in shape, depending on perspective -- the point being that the angular velocity of the objects wrt the Sun never changes sign.

And of that set of objects, ten are spherical due to their own gravity. So, IMVAO, the Moon should be counted as a tenth planet.

Who gives a rat's ass?

[RareHeintz]

I've seen a few posts where people seem to be getting pretty worked up over whether or not Pluto is getting what amounts to Full Member or Associate Member status in the Solar System. The question nobody seems to be asking is: Who cares?

Whether or not Pluto gets labeled with the "p" word is not, to my thinking, significant. It's still a major object in the Solar System, and should be mentioned during everyone's science education, just like more minor (but still significant) non-planetary objects such as Eros, Phobos and Deimos, or the better-known comets. The more interesting point to this story is not what someone chooses to call Pluto, but the proportion of ignoramuses who don't know it exists to begin with.

For those who can't get over the question of whether or not Pluto is a planet, I suggest that we should leave its status open to question, like a certain letter of the alphabet:

Vowels: A, E, I, O, U, and sometimes Y.
Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and maybe Pluto.

OK,
- B
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