Two More Moons Discovered Around Pluto

clayj said:
The two new moons are between 30 and 100 miles (45 to 160 kilometers) in diameter, Weaver said. There is not enough data to pin their size down exactly, however. Pluto is 1,430 miles wide and Charon's diameter is about 730 miles.
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Between 30 and 100 miles round? I wonder if they're like Phobos and Deimos (the two moons of Mars); so small that they don't have enough gravitational force to be round.
 
wordmunger said:
If that's what bothers you about scientists, you may as well give up on science. Science is constantly changing as our awareness of the universe changes. I think the original discoverers of Pluto just got excited that they found something new orbiting the Sun, and made a mistake by categorizing it as a planet. We're all used to thinking of nine planets, so it's been a tougher task for scientists to convince us that Pluto isn't a planet.

It's kinda like how the guy who named the "brontosaurus" made a mistake and didn't realize there was already a name for it -- "apatasaurus." But "brontosaurus" was already in all the textbooks, and we still have a tough time convincing people that the real name is "apatasaurus."
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I see your point (and it's a good one).
I'm not sure what made Scientists re-consider Pluto, but it just seems like such a simple problem to solve. There is already a definition of what a 'Planet' is, therefore we must ask ourselves "does Pluto meet these qualifications?" It either does, or doesn't. I just don't see where the uncertainty is.
Maybe someone can explain this better to me.
 
Totally off topic, but when scanning the page, my eyes initially read the topic as Two Morons Discovered Around Pluto. Heh. :rolleyes:
 
bankshot said:
Totally off topic, but when scanning the page, my eyes initially read the topic as Two Morons Discovered Around Pluto. Heh. :rolleyes:
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Nah, Balmer and Gates are still in Redmond. :(
 
EricNau said:
There is already a definition of what a 'Planet' is, therefore we must ask ourselves "does Pluto meet these qualifications?" It either does, or doesn't. I just don't see where the uncertainty is.
Maybe someone can explain this better to me.
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The thing is, there isn't an accepted definition of what a planet is. The original term was for objects that moved relative to stars, but that started getting to be a big list with asteroids and comets, etc.

From Space.com:

http://www.space.com/scienceastronomy/sedna_pluto_040317.html

Until now, scientists have not had a set definition for the term "planet." In recent years, many potential parameters have been kicked about, from an object's roundness to its distance from the Sun and the shape of its orbit. Even where it formed is a consideration.

Now with Sedna, which is around 75% of the size of Pluto, we're either going to have a sentimental 9 planets, or open it up to other trans-neptunian objects. This could get messy!

There's also a question of whether to consider Pluto and Charon a planet and its moon or a dual planet system. One does not so much revolve around the other as they revolve around each other because of how close to each other they are in size. Earth and its Moon also do a bit of the dumbell thing.
 
jayscheuerle said:
There's also a question of whether to consider Pluto and Charon a planet and its moon or a dual planet system. One does not so much revolve around the other as they revolve around each other because of how close to each other they are in size. Earth and its Moon also do a bit of the dumbell thing.
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I'd say planet definition based on gravitational forces is pretty much useless since every object with mass exerts a gravitational force of some measure on everything else (heck, we even exert a miniscule pull on the earth). I suppose the only way you could do that is by defining a planet as a celestial body whose primary gravitational influence is a star (but even then, many stars themselves fit that definition). Perhaps then a non-star celestial body, but then that would count comets and many asteroids. Astronomy can be quite the difficult science to deal with. :p
 
I think the most logical (and simplest) way to define what is a planet is its diameter. Above some value "x", it's a planet; below "x", it's something else.

I don't think anyone would dispute that asteroids (Vesta, Eros, etc.) are not planets... so the area of dispute centers around Pluto. If Pluto is a planet, then the farther out object must ALSO be a planet, since it's larger than Pluto. So, we either have 10 planets (the usual 9 + the new one) or we have 8 (everything out to Neptune).
 
jayscheuerle said:
The thing is, there isn't an accepted definition of what a planet is. The original term was for objects that moved relative to stars, but that started getting to be a big list with asteroids and comets, etc.
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OK, that is my complaint, that they should just make up their minds. I don't know how (maybe they should vote on it or something). :p
Just seems like it would be easy to figure out, it's not like they are arguing if the theory of evolution is true or not, really they are just arguing over the definition of a word.
Couldn't their time be spent a little better?
 
EricNau said:
OK, that is my complaint, that they should just make up their minds. I don't know how (maybe they should vote on it or something). :p
Just seems like it would be easy to figure out, it's not like they are arguing if the theory of evolution is true or not, really they are just arguing over the definition of a word.
Couldn't their time be spent a little better?
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Obviously, they ARE spending their time doing something better than worrying about how to define a planet. Whatever it's designated as will do nothing to change its properties. Call everything that revolves around our sun "Solar Bodies" and be done with it. "Planets" is so... 20th century!
:p
 
In terms of classification

I forgot to mention the unofficially named "Xena", whose orbit is tilted at around 45 degrees and is 50% larger and 3 times further away than Pluto.

More to be found I'd bet...
 
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