like what you said, mercury used to be the lower limit of planet size, now it's pluto.
If you ask any astronomer: what is a planet?? I think not all of them will give you the same answer... I think the most common answer is that a planet must rotate around a star and must be "large". Ya... the moon is larger than pluto! So who knows what that "large" mean!
Anyway, there are a lots of this type of gray area in astronomy. Hope astronomers can come out with a new definition of what is a planet.
Have a nice day.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
i dont think there will be a clear definition for a planet, most common people would be too reluctant to have pluto demoted to a planetoid.
Honestly, i think that pluto is simply a planetoid (or a mesoplanet as AGMI called it). Its elliptical orbit makes its status questionable. Size doesnt matter much though. It is probably the mistake of the IAU to crown pluto as a planet in the race for more planets and they arent gonna admit it too soon, even the church took quite a long time to recitify galileo......
Actually its not what NASA say,its what IAU say. What IAU say, we follow lor. Currently, IAU has no plan to 'demote' pluto or 'promote' objects like Ceres.
Lets see..Pluto Has an atmosphere compisition like that of a comet and follows an elliptical orbit..imagine if somehow it's orbit gets pulled in till it becomes a sungraver :o what a spectacle
Do You Believe That Forks Are Evolved From Spoons?
This is my opinion on the matter, does not represent the truth!
Until now there still isn't a "lower limit" for planets. Pluto still isn't recognised as the lower limit, not yet anyway.
I think that Pluto was discovered and first named a planet when we did not realise that there are other planetoids around. It therefore should still remain known as a planet. If renamed, it might create an uproar among the astronomy community. I think by letting our past mistakes live as an exception is a better way to handle this situation. For Sedna and the newer found whatever-you-call-them, yea I agree tho follow the IAU, and they are agreeing on calling them planetoids right? So I follow.
AGMI wrote:Lets see..Pluto Has an atmosphere compisition like that of a comet and follows an elliptical orbit..imagine if somehow it's orbit gets pulled in till it becomes a sungraver :o what a spectacle
you mean sungrazer? I dont think it will happen though, Neptune only causes it to wobble a bit due to the distance between them. Even if all the planets were to line up and pull at pluto, it only results in stronger wobbling i think..
Even if the planets all line up, the net gravitational pull will be negilible. Whether if its a planet whatsoever, i cant see it in my telescope, i don't care.
Charlie
The gentle light of a distant galaxy
must needs pour into mine eye.
Or i shall with bent and turned,
fall me down, distraught..To die.
Hi,
By September 2006, our Solar System will go through a "man-made disaster event"... This event might change our Solar System forever and we might "lost" our planet Pluto or suddenly had a few more planets... err... at least on paper... ha ha ha More detail: http://www.space.com/scienceastronomy/0 ... ition.html
Finally, IAU are going to decide whether pluto is a planet or not, so by September 2006, we might have 8, 10 or more planets!! Also, the IAU are going to officially defining the word "planet"... Now we had a standard answer when someone ask us what is a planet... hee hee
Hmm... Just wonder will all those primary and secondary school student require to take their science paper again if pluto lost it planetary status?? ha ha ha
Have a nice day.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." 
