Monday, August 24, 2009

Is Pluto a Planet?

The great debate continues and the tender crushed hearts of school children are again torn asunder by scientists who "vote" on whether or not the definition applies. There is no scientific consensus, really. Those of us who learned there were 9 planets orbiting the Solar System when we were in school still harbor that secret magic number. The US State of New Mexico's legislature resolved that Pluto is still a planet.



Scientists are torn because there are Kuyper Belt Objects (KBO's) larger than Pluto out there in the further reaches of the Solar System. The New Horizons Mission to Pluto may stir the hearts of scientists to reconsider their harsh down-grade. There's also the dwarf planet, Ceres, that is orbits in the asteroid belt between Earth and Mars. The Dawn Mission to Ceres is likely to create a groundswell of support for calling Ceres a planet when we take a closer look at the place. 

In order to be classified as a "genuine" planet, the object must be:
  1. Massive enough that gravity crushes it into a round(ish) sphere. (Pluto is smaller than Earth's Moon)
  2. It must orbit the Sun.
  3. It must be dominant enough that it clears away objects in its orbital space. (this is the sticking point, apparently because scientists can't agree on the cleanliness of Pluto's orbital path)
Sound off here: Planet/Not a Planet??


WoFat said...

No, silly, Pluto is a cartoon dog. Don't you know nothing?

darlin said...

LOL WoFat!

I still say that Pluto is a planet, this is what I was taught in grade school and teachers are always right! :-)

Opus #6 said...

Pluto NEEDS to be a planet. Simply because we Earthlings need more real estate.

LL said...

Sedna, Eris (which has its own moon), Ixion, Varuna Orcus and Quaoar are all **about** the same size as Pluto and they're in the Kuiper Belt too. Ceres is much closer to Earth than either Mars or Venus and its mass is such that it's a spheroid.

But all that said, Pluto is a planet and always will be!

Quantumleap42 said...

I was surfing blogs and the title of your post caught my eye because I am an astronomer, so I hope you don't mind my throwing in my 2 cents worth (or my 25 cents worth depending).

First to understand why they decided to change the naming convention we have to consider the historical perspective. When the first asteroids were found they were also called planets. This continued until about 1858 or so when there were officially 60 or so "planets" with more being discovered every year. This presented a problem because the asteroids were concentrated in a specific location and they acted differently from all the other "historical" planets. With increased understanding about our solar system astronomers realized that they needed to come up with a different system to reflect the new understanding of how our solar system worked. Thus they came up with the designation "asteroid" for the smaller bodies.

Now about 150 years later we are again finding out more about our solar system. With this increased understanding we need a better system to allow us to make sense of what we are seeing out there. I few years ago I was at a conference for the American Physical Society and one of the speakers was explaining all of the recent discoveries they had made. They have literally found over 100 Kuiper Belt Objects that were potentially the same size if not bigger than Pluto, with many, many more out there. To reflect this changing understanding of our solar system and to reflect our expanding knowledge about other planetary systems (i.e outside our own solar system) we (the astronomical community) decided that it was necessary to come up with a consistent and more mathematically driven definition of what a planet is. Thus we changed the definition to suit our new understanding and in the process Pluto got a name change (not a demotion, just a name change).

As a side note, the location of the American Physical Society conference that I mentioned was in Flagstaff, Arizona which is the site of the Lowell Observatory where Pluto was discovered. Let's say that the people that work at the observatory are very defensive of Pluto, and are not happy about the change in the designation. Almost all other astronomers are happy about the change.

Also as a final side note, in Europe the change in the status of Pluto from a planet to a dwarf planet has not met with all the resistance that it has met here in the US. This is due almost entirely to the association with the dog. Because the dog was so popular in the US it automatically made the planet one of the most popular. Thus when they decided to no longer call it a planet people in the US got upset because it was their favorite planet/dog. And people in Europe are scratching their heads wondering what all the fuss is about.

LL said...

I am not sentimental about Mickey's dog.

It's merely the tradition.

I know it's a KBO, but it's part of Americana, the cartoon dog aside.

Xmichra said...

I answered this some time ago as an aferthought... if you are interested.

love the blog, btw.

JT Grachek said...

Who cares, it's a damned rock.

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