Planetary Debate
Robert already beat me to this, but since I had the whole thing written for my Xanga account, I'm going to post it here ANYWAYS! So THERE!
So, you may have heard about the debate going around about what's a planet and what isn't. Basically, astronomers are thinking about defining "planet" as "any celestrial body that has enough mass to gravitationally pull itself into a rough sphere". They're also defining a "moon" of such a body as "any celestrial body that revolves about a planet such that the common center of mass of the moon and planet lies within the planet itself".
Trouble with this is, that makes 3 new "planets" that we know of within our solar system: Charon (Pluto's "moon"), Ceres (the largest asteroid in the asteroid belt), and "Xena" (an asteroid out by Neptune that's larger than Pluto is). Plus, of course, there might very well be OTHER objects like "Xena" (the name may not be permanent -- unfortunately!) that will, in future years, become "planets" as well. I would HATE to be a science teacher in such a situation! "Come on, kids! Let's practice our planets! Who knows the 34th one from the Sun?" (Right now, that is. Things like Xena are in complicated orbits and will end up switching their order over the years, just like Pluto and Neptune switch.)
I guess I just have issues with this! Of course, that's not new. I had an astronomy professor at Minnesota who VEHEMENTLY believed that Pluto should not be called a planet. At the time, I just shook my head and smiled at him for his eccentricity, but now that I've had time to think about it, he has a point.
After all, the inner planets (Mercury, Venus, Earth, and Mars) were formed in a different manner (or, rather, at a different time) from the outer gas giants. The inner planets are rocky because they had their atmospheres blown away by a huge gust of solar wind right as the sun itself became a true star. The outer (ie: colder and more solidified) planets were able to hang on to more of their lighter elements, and became gas giants. Pluto, needless to say, was not formed this way -- that's why it's rocky and small. It's probably a captured body. Charon and Xena are too.
I guess, in my opinion, it's not just size or distance that matters. It's also the way they were formed. There might be an argument for Ceres, I guess, just because it WAS formed in the same way as a "regular" planet, and got torn apart by tidal forces (and/or impacts) mid-formation. Of course, by that theory, our own Moon should ALSO be a planet, since it's really just a piece of the Earth that got torn off by a collision...
In any case, I find the whole discussion rather trivial. There's so much more out there to explore -- you'd think that astronomers would be more interested in that than in what to NAME things!
Oh -- and I just think I need to post John's reply to the whole planetary debate:
"I hereby declare Texas a planet. It's round(ish), and anybody who lives here will tell you its motion is completely self-centered."
That cracked me up! Ten bonus points to John!
So, you may have heard about the debate going around about what's a planet and what isn't. Basically, astronomers are thinking about defining "planet" as "any celestrial body that has enough mass to gravitationally pull itself into a rough sphere". They're also defining a "moon" of such a body as "any celestrial body that revolves about a planet such that the common center of mass of the moon and planet lies within the planet itself".
Trouble with this is, that makes 3 new "planets" that we know of within our solar system: Charon (Pluto's "moon"), Ceres (the largest asteroid in the asteroid belt), and "Xena" (an asteroid out by Neptune that's larger than Pluto is). Plus, of course, there might very well be OTHER objects like "Xena" (the name may not be permanent -- unfortunately!) that will, in future years, become "planets" as well. I would HATE to be a science teacher in such a situation! "Come on, kids! Let's practice our planets! Who knows the 34th one from the Sun?" (Right now, that is. Things like Xena are in complicated orbits and will end up switching their order over the years, just like Pluto and Neptune switch.)
I guess I just have issues with this! Of course, that's not new. I had an astronomy professor at Minnesota who VEHEMENTLY believed that Pluto should not be called a planet. At the time, I just shook my head and smiled at him for his eccentricity, but now that I've had time to think about it, he has a point.
After all, the inner planets (Mercury, Venus, Earth, and Mars) were formed in a different manner (or, rather, at a different time) from the outer gas giants. The inner planets are rocky because they had their atmospheres blown away by a huge gust of solar wind right as the sun itself became a true star. The outer (ie: colder and more solidified) planets were able to hang on to more of their lighter elements, and became gas giants. Pluto, needless to say, was not formed this way -- that's why it's rocky and small. It's probably a captured body. Charon and Xena are too.
I guess, in my opinion, it's not just size or distance that matters. It's also the way they were formed. There might be an argument for Ceres, I guess, just because it WAS formed in the same way as a "regular" planet, and got torn apart by tidal forces (and/or impacts) mid-formation. Of course, by that theory, our own Moon should ALSO be a planet, since it's really just a piece of the Earth that got torn off by a collision...
In any case, I find the whole discussion rather trivial. There's so much more out there to explore -- you'd think that astronomers would be more interested in that than in what to NAME things!
Oh -- and I just think I need to post John's reply to the whole planetary debate:
"I hereby declare Texas a planet. It's round(ish), and anybody who lives here will tell you its motion is completely self-centered."
That cracked me up! Ten bonus points to John!