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New Tenth Planet Has a Moon
starexplorer writes "SPACE.com is reporting that the recently discovered 10th planet of our solar system has a neighbor - a moon. The discovery team also have nicknamed the planet 'Xena' and the moon 'Gabrielle'. Many scientists are objecting to whether the new planet really is a new planet - so what do you call a moon with no planet?"
A body that orbits another body is a satellite in all cases. It is a moon if the body it orbits is a planet. Either "Xena" is a planet, or Pluto isn't (in which case Charon isn't a moon, either). The really interesting question for me is whether there are a lot more planet-sized bodies so far outside the ecliptic.
How close to a perfect sphere must it be? When you're getting into classification, items like that cause major problems.
Personally, I favour 1) Must orbit a star 2) Must have sufficient mass to maintain an atmosphere (ignoring effects of solar wind) 3) If partnered with another body, the center of orbit must be within its diameter. I think requirement 2 probably covers 'spherical' well enough.
Of course, I'm not an astronomer.
As far as I known, Xena (2003 UB313) is not a planet yet.
Mike Brown, who discovered it said "If Pluto is a planet, so is 2003 UB313". (And he said 6 months earlier that Pluto should not be considered a planet !)
But in fact, they are both transneptunian objects. Along with some big ones we discovered earlier like Quaoar and Sedna. So what's the difference with Xena ? It's that Xena is the first transneptunian object larger than Pluto. But note that it's possible to have transneptunian objects the size of Mars. Size don't matter as they are still transneptunian objects, part of the Kuiper Belt.
But you say "Xena has a moon". So what ? Even asteroids can have moons. No big deal.
So the true question is "Is Pluto still a planet ?".
A lot can be said, but I'd say Xena and other transneptunian objects aren't planets while Pluto is.
Why Pluto ? Only because from an historical and cultural point of view, it's a planet.
Gee, can these name choosers at least give a minimum of coolness? Huge continent-sized lumps of rock in space should at least have some weighty, dignified name. I mean, think of what we would be doing in the future. Will people ever be able say 'Invaders from planet Buffy' with a straight face?
And what if we find life? I'd assume the inhabitants of a planet named after characters in a TV show can be quite offended. I propose we go back to good old fashioned Gods and Goddesses.
I think the scientists could have auctioned off the names of the new objects to pay for further space exploration, better telescopes, etc.
Here's an example: a species named after goldenpalace.com (an online casino):
http://www.msnbc.msn.com/id/7493711/
http://www.thebricktestament.com/the_law/when_to_
This is all stupid, and it all falls out of our need to categorize everything, usually on the wrong criteria.
So, you have stars, and they're easy to identify because there's this whole fusion reaction that gives off a lot of radiated energy. Everything that is too small to start the reaction is just in a different category - "not a star".
Falling into the "not a star" category within our solar system, all of the observed objects have parameters that are continuous variables, not categorical. Earth and Mars are more similar than Earth and Jupiter, but they're not the same, and neither can we put them in the same category.
So, stop calling them planets... just call them objects. Earth is a satellite of the sun. The moon is a satellite of Earth. Planet is a pointless definition anyway, based on how humans started discovering the universe, rather than what we now have as a model.
"I have never let my schooling interfere with my education." - Mark Twain
And a lot of us really didn't like "Mostly Harmless". Even Adams admits it was a bleak book due to some problems in his life, and wanted to write a more upbeat sixth book, but he didn't get the chance.
IMHO, since we are having such a debate as what is a planet and what is not, then the notion of a planet has outlived its usefulness. Out of all of the large rocks orbiting the sun, why select some to be called planets and others not? Is there a need to draw such a distinction? Labelling some objects as planets and others as not is as ridiculous as deciding upon "x" meters of string to be known as a standard long or short piece.
If you say we need "planets" so that objects may be easily classified, then I sat that the application of the data determines the measurement for classification. And there are countless measures such as size, mass, distance from the sun, eccentricity, angle from the ecliptic, or any combination of these and more.
The question of whether a computer can think is no more interesting than the question of whether a submarine can swim.
The problem here is not one of underclassification, its one of overclassification. We are classifying things to a level beyond which our theories are solid enough to prove. Thus, as we discover and understand more, we face the problem of having wrongly taught generations of people who now protect what they "know" because, after all, they never teach anything wrong in school.
Unless they can come up with a concise definition that doesn't sound like someone is simply trying to justify their historical bias, perhaps we should just solve this by dropping the word "planet". We could just make everything a satellite and perhaps go the one step further of including the largest body it orbits. So, all of the planets become solar satellites and our moon becomes a mere Earth satellite.
True enough. I guess one could refer to them as satellites of the Big Black Hole in the middle of the core.
It seems a bit of a stretch, but...
Yes, it was "satellite" in Medieval French too: the commenter didn't specify when the mistake was made. Maybe the mistake was to interpret a false singular nominative "satillite" from accusative "satellitem" as Latin turned into the Romance languages; or maybe someone on Rome did it. Etymology is always relevant! It tells you things like, for instance, the word "satelles" itself was actually first used to refer to the companion of a planet in exactly that form: by Kepler, in 1665, referring to the moons of Jupiter. I think it's particularly poetic for him to use the latin for "bodyguard": oh that astronomers were as inventive now.
We first noticed planets were different from stars because we could resolve them into DISCS, not merely points of light
Umm, no we didn't. We first noticed planets were different from stars because planets don't move in the same orbit as stars. They move in one direction, then they zig zag back in the other direction. The word planet comes from the Greek word plants, which means "wanderer". The actual phases of the planets weren't discovered until much much much later.