A Planet by Any Other Name
Remember a few years back when there was a brouhaha over whether Pluto should be considered a planet? The International Astronomical Union, the body that decides, among other things, on the official names of astronomical objects and features, has been working on a new definition of the word “planet”. The results of their deliberations should be known by the end of September.
The reason there is some confusion is because we have discovered a population of icy worlds orbiting beyond Neptune that have much more in common with Pluto than Pluto does with any of the other planets. In fact, some of these new worlds (prosaically called Kuiper Belt Objects or KBOs), are in the same special orbital relationship with Neptune that Pluto is. These have been dubbed Plutinos. Recently a KBO was discovered that is bigger than Pluto, but on an orbit that is even more unusual (as far as planet orbits go, which is to say, nearly circular) than Pluto’s. The matter is complicated by the discovery over the course of the past decade or so of scores of extrasolar planets, that is, objects orbiting stars other than the Sun. Some of these blur the line between planet and star just as some of the KBOs blur the line between planet and ice cube. To make things even more fun, when KBOs occasionally get scattered into the inner solar system they start to evaporate as they near the Sun, and we call these objects comets. So should we call KBOs comets? Should we call Pluto a KBO? Should we call of them planets? Or come up with another name for the KBOs (for one thing, there are certainly KBOs around other stars, and it would be a bit peculiar naming all of them after our own backyard Kuiper Belt).
Personally, I favor demoting Pluto from the ranks of the planets, and I expect that the IAU definition will do just that. There is simply no sensible physical definition of a planet that includes Pluto and does not also include countless other objects in the outer solar system. Let’s reserve “planet” for the big guys. But, Pluto by any other name is still just as interesting a place to explore, and when the New Horizons spacecraft goes zipping by in 2015 it will undoubtedly teach us a lot about the origins of our solar system, planets, ice cubes, and all.
August 7th, 2006 at 11:18 am
I said above that it’s hard to come up with a definition that includes Pluto and does not also include many other objects. Basically, I think whatever definition is chosen, the number of planets in the solar system will no longer be 9. Demoting Pluto would allow the number to reasonably remain 8, but it is also possible, maybe even likely given the unpopularity of the idea of demoting Pluto, that they will make the definition more expansive, including Pluto and many other KBOs and perhaps some asteroids as well.
August 16th, 2006 at 11:30 pm
I have to agree with you on demoting Pluto. The newly proposed criteria is too inclusive; conceivably, we could have hundreds of planets in our solar system.
Hell, even Charon and the asteroid Ceres are up for promotion! Ugh.
My feeling is that anything still in its native debris field is not a planet, so no asteroids or KBOs. If it were really a planet, it would have cleared its own swath of debris away.
August 17th, 2006 at 11:48 am
They want to demote Pluto simply because they can. A heady power trip for dolts tethered to desks.
Leave Pluto alone. Its planetary status is a historical (arti)fact. Go pick on something your own size.
February 28th, 2007 at 6:22 am
i like the idea of calling all KBO’s ‘oboloi’, after the coins placed withthe dead to pay Charon for ferrying them across the river to pluto’s kingdom….and then ‘Kuiper belt’ can be the generic term we use for our, and other, solar systems..
March 4th, 2007 at 4:56 am
“Oboloi”, eh? Reminds me of The War of the Worlds and the Eloi.