What's in a...planet?
Yep, you heard right. Planets. Those things that orbit the sun, have their own gravity and usually at least something of an atmosphere. We all know them, they've been around since...well...the beginning.
Only here's the thing: some wonderful gurus who know more about our universe than the average person can't seem to agree on what a planet is. No kidding.
The debate has really become important for a couple of reasons:
#1: Pluto has this "moon" - Charon (the name no one knows how to pronounce). But Charon is almost as big as Pluto, has a similar gravitational pull, and, well, kind of affects Pluto's orbit as much as Pluto affects Charon's.
#2: There's another big object recently discovered beyond Pluto: it's not been officially named yet, but it's there and demanding attention (as well as a classification).
#3: Apparently (and I missed this one myself), there's a large asteriod in the belt between Mars and Jupiter that has planet-like qualities. I knew Ceres was out there, but I had no idea that people wanted it to be re-classified. Like that's going to go over well with the populace of the our planet to have to relearn the order of the planets. I mean, we adjusted well to adding on Pluto in the mid 1900's, but we've been conditioned to Mercury, Venus, Earth, Mars, Jupiter, etc. Who's really going to remember Ceres? lol
A friend of mine linked me to this very interesting website kept by an astronomer: "Bad Astronomy". There's lots of good info there. He quotes directly from the commitee and also gives his own rebuttals.
And let's face it, he's qualified to explain this to you. Not me; I'm just a novice, a fan. (Have been as long as I can remember.)
But I wanted to ask for your opinion. What do you think: just what is a planet?? What conotations does this term have for you?
Only here's the thing: some wonderful gurus who know more about our universe than the average person can't seem to agree on what a planet is. No kidding.
The debate has really become important for a couple of reasons:
#1: Pluto has this "moon" - Charon (the name no one knows how to pronounce). But Charon is almost as big as Pluto, has a similar gravitational pull, and, well, kind of affects Pluto's orbit as much as Pluto affects Charon's.
#2: There's another big object recently discovered beyond Pluto: it's not been officially named yet, but it's there and demanding attention (as well as a classification).
#3: Apparently (and I missed this one myself), there's a large asteriod in the belt between Mars and Jupiter that has planet-like qualities. I knew Ceres was out there, but I had no idea that people wanted it to be re-classified. Like that's going to go over well with the populace of the our planet to have to relearn the order of the planets. I mean, we adjusted well to adding on Pluto in the mid 1900's, but we've been conditioned to Mercury, Venus, Earth, Mars, Jupiter, etc. Who's really going to remember Ceres? lol
A friend of mine linked me to this very interesting website kept by an astronomer: "Bad Astronomy". There's lots of good info there. He quotes directly from the commitee and also gives his own rebuttals.
And let's face it, he's qualified to explain this to you. Not me; I'm just a novice, a fan. (Have been as long as I can remember.)
But I wanted to ask for your opinion. What do you think: just what is a planet?? What conotations does this term have for you?
affiché par petite américaine à 18:47
I didn't know you were interested in this stuff (this, and the next entry.) Neat!
I find myself being very linguistically conservative, and wanting to say that a planet is what we've been calling a planet. Also that at 200 miles (or so) Ceres is just too darn small. But my systematic side can see the logic of the "orbiting the star and round due to self-gravity" definition. But there's a competinng definition, of being able to gravitationally dominate its orbit, which also makes sense, and would rule out Ceres. This is when conservatism seems pretty attractive. Caling Pluto/Charon a double planet seems pretty natural, though; we've had such things in science fiction, be nice to have one in our own system, and it fits the facts (they orbit a point outside of Pluto; the Earth and Moon "orbit" a point within the Earth, though not the center.)
As by far the biggest asteroid, though, and as of recently thought to contain ice, Ceres is a big deal to anyone who thinks about colonizing the solar system.
Yeah, I'm an astronomy dork. But only an amature dork. ;)
I have to agree. I, too, have a conservative (or perhaps "traditional" would be a better term) linguistic perspective of our word "planet".
You have some good points, and I generally agree. But I wonder if we make an official definition of planet that specifically mentions an orbit point for a "moon", what would our ancestors do when the moon no longer orbits around an official point inside the Earth?? Just too wierd to think about.
And I just think making Ceres a planet is wierd. WIERD!! But you're right: it would be a high contender for an outpost. Hmmm...does it have any other resources other than water, I wonder?
Wikipedia powers activate!
Ceres diameter of about 950 km, rather bigger than I'd said, not much smaller than Charon. 1/3 of the mass of the asteroid belt, though the whole belt is 4% of the Moon's mass. Allegedly more fresh water than the Earth (most of the Earth's water not being fresh, of course.)
As for other resources, I don't know. Generic rocky asteroid I'd guess, which is actually a lot of resources to the right technology: silicon, aluminum, calcium, magnesium, sodium, some iron, just for the common elements, and of course the vast excess of oxygen. (Third most common element in the universe.) Nothing unique there, of course. But rarer elements might have been concentrated into ores at some point by the water, without miners having to deal with the gravity wells of Earth and Mars; that could be valuable.
If the Moon's drift away causes the orbital dynamics to change, then our descendants calling it a double planet might seem not so weird. I was using 'conservative' as "resisting unnecessary change", but if reality *does* change...