So it depends on how you define a planet. It seems that some scientists dispute the IAU definitions of what constitutes a planet and propose a new definition that would make Pluto a planet again but also mean that some moons are included.
Source: https://www.youtube.com/watch?v=8-2HxrgqUnM
General / Off-Topic So Pluto may be a planet after all?
- Thread starter insanephoton
- Start date
expanding the definition of something rarely leads to that word being better off for it. You end up just reducing the information transmitted in using the word.
The current definitions are better in that sense. we have a word for planets and a definition for dwarf planets that describes the situation in a more concise way than a definition that would encompass far more than desired.
The current definitions are better in that sense. we have a word for planets and a definition for dwarf planets that describes the situation in a more concise way than a definition that would encompass far more than desired.
sorry i didn't even know it was taking off the planetary list.
They should just keep the current definition, and make Pluto an honorary planet
Worked out well for them.
IAU definition of planet - Wikipedia
Maybe the word planet (planetes; wanderer) is losing its usefulness as we have learned more about solar system(s)?
That's why the definition was refined. Seven or eight, or twenty planets are easier to keep track of than thousands.
Trick is finding a definition that can be consistently applied and that isn't purely arbitrary.
I honestly have my doubts about Pluto being affected in any way by the way we call it. It's still dangling out there on the far edges of the Solar system, just like it was yesterday.
They should just keep the current definition, and make Pluto an honorary planet
"A rose by any other name would smell as sweet". The only noticeable difference between many astronomical bodies is size/mass and the resultant effects on matter formation and behaviour. Asteroid/minor planet, satellite, dwarf planet, gas giant, brown dwarf, star.... all much of a muchness besides their size.
The universe doesn't care what we call them.
Elite: Dangerous's maps just call them planets even if they're small satellites.Maybe the word planet (planetes; wanderer) is losing its usefulness as we have learned more about solar system(s)?
I watched that and, while better than the current system, I still disagree with the proposed new definition. I think it goes too far the other way. The goal is to convey information in a way that is quickly and easily understood, clumping planets and moons together just complicates the process IMO, why would you want someone to think that Titan is a planet with the historical presumption that planets orbit around a star independently? Then there has to be secondary question about whether it orbits a parent planet or not.
In my mind it is simple: if it orbits a star and looks mostly round, you know, like a planet, it's a planet. If then there is another body that orbits around that planet, then that's a moon - I know, tricky stuff so far. If two celestial bodies orbit each other then they're both planets in a binary planetary system. If there's two celestial bodies that orbit each other but both orbit a planet, then it's a binary moon system. Etc..
At this point you can create a size scale, for planets; 1-x - x representing any size from Ceres to Jupiter and beyond. For Moons; M1-Mx - again x representing the same as for planets, but likely not to get as high up in numbers for obvious reasons. These can be based on percentage ratios with Earth's size as the starting point for both planets and moons, Earth = 0, smaller is -1 etc, bigger is +1 etc.. Work out a good mathematical basis that you don't need a supercomputer to understand, ie; that allows someone get a sense of scale of what a +5 planet or a -3 moon is in their mind. Then add any other discernible characteristics and you can adequately describe any object that is round(ish) in any system in one go. If you want to only consider the major planets, then slide the scale accordingly to find the type you are looking for, if you want to only consider the minor planets, do the same the other way. Repeat for moons.
I don't know, maybe the above is too simplistic and doesn't make one feel smart enough if one understands the differences compared to those who don't.
In my mind it is simple: if it orbits a star and looks mostly round, you know, like a planet, it's a planet. If then there is another body that orbits around that planet, then that's a moon - I know, tricky stuff so far. If two celestial bodies orbit each other then they're both planets in a binary planetary system. If there's two celestial bodies that orbit each other but both orbit a planet, then it's a binary moon system. Etc..
At this point you can create a size scale, for planets; 1-x - x representing any size from Ceres to Jupiter and beyond. For Moons; M1-Mx - again x representing the same as for planets, but likely not to get as high up in numbers for obvious reasons. These can be based on percentage ratios with Earth's size as the starting point for both planets and moons, Earth = 0, smaller is -1 etc, bigger is +1 etc.. Work out a good mathematical basis that you don't need a supercomputer to understand, ie; that allows someone get a sense of scale of what a +5 planet or a -3 moon is in their mind. Then add any other discernible characteristics and you can adequately describe any object that is round(ish) in any system in one go. If you want to only consider the major planets, then slide the scale accordingly to find the type you are looking for, if you want to only consider the minor planets, do the same the other way. Repeat for moons.
I don't know, maybe the above is too simplistic and doesn't make one feel smart enough if one understands the differences compared to those who don't.
Last edited:
Yebbut technically that's not how orbits work. Both orbit around their mutual centre of gravity, the barycentre. Even the Earth (Terra) and Moon (Luna) do. It just happens that the barycentre in our case is inside the Earth (just) but if the moon were larger or our planet smaller then it might be between both.
In the end, it's just words. As a wise man once said, "Only in mathematics will you find truth".
Pluto and Charon are a binary, not necessarily a planet and a moon. Basically the only binary planetary duo in the Solar System
But no, it's not a planet because "it didnt cleared its neighboring region of other objects"?
What's that even mean? Does that definition invalidate any binary planetary system?
Where's this "it's just words" stuff coming from? Words matter when it comes to communication and education. Numbers are words too btw.
An arbitrary division between minor, dwarf and major planets - based on a system of just 8 (or 9) of the latter, which keeps changing anyway... well, its arbitrary and doesn't affect and decisions. Some words are more important than others. "Planet" actually means "wanderer", so any body except stars is a planet.
Oh, and you do know there are only two elements in the universe that aren't metals, according to astronomy? I bet you don't use that word properly either...
Using the Pluto definition also means Earth is not a planet. We haven't cleared our orbit.