Depth perception in a vacuum is more difficult too. A cleverly painted basketball could look like a planet from your spacecraft's windows. If we gave such a basketball a name-tag that said "Pluto", would people argue for its status as a planet?
"It has clouds" is a terrible reason to define something as a planet. Triton has clouds, but it isn't a planet. Titan's surface isn't visible because of how thick the cloud layer is, but nobody is arguing that it's a planet. Saying "Pluto looks like a planet so it is one" is unscientific and kind of insane.
Its the only body named after a cartoon dog.
Its the only body named after a cartoon dog. For that alone, it should get reinstated. Have these astronomers no sense of humour?
N.
As Star Trek navigator, I would never call Pluto a planet, but then, in TNG, even a Pluto with a much denser atmosphere would be considered to be an asteroid.
Dr. Alan Stern, as chief science officer on the starship would call it a planet.
Bob Clark
"It has clouds" is a terrible reason to define something as a planet..
But "It has clouds" combined with "It orbits the Sun" is quite convincing. That wouldn't demote any of the classical planets, and also would not promote anything in the Asteroid belt or Kuiper Belt (unless Ceres or Sedna could be shown to have atmospheres).
In other words: if it orbits the sun, it might be a planet (Ceres isn't). If it has an atmosphere, it might be a planet (Titan isn't). If it meets both, it is certainly a planet.
A coma is not the same as an atmosphere: it is not gravitationally bound to the comet.What about comets?
As I said, by itself it doesn't. But when a gravitationally bound atmosphere is combined with a solar orbit, in my opinion the rest of the requirements should be waived and the object should be considered a planet. Mercury is a planet because, while it does not have an atmosphere, it meets the IAU requirements that excluded Pluto.Again I ask, why should clouds influence the definition at all?
No...Titan isn't a planet because it orbits Saturn, not the sun.Titan isn't a planet because it doesn't function like a planet.
I don't see why any of those things should be a factor.In the path it takes around the sun, it comprises a minute fraction of the mass and directly controls almost nothing. Saturn is the dominant body here, affecting planetary/gravitational dynamics strongly enough to be comparable only to other planets.
I would be a smart-aleck here to accuse you of suggesting that Pluto orbits Neptune. We all know better than that, and I don't think you are saying that. But...what exactly are you saying with that?Like I said before, Pluto doesn't even come close to affecting other bodies the way a planet does. It is controlled by Neptune. Their orbital resonance is locked in by Neptune's influence on Pluto, not Pluto's influence on Neptune. Just as it would be ridiculous to call Triton or Titan planets, it's ridiculous to call Pluto a planet, as it just is not functionally a planet at all.
Umm...no. While I mentioned that anything that meets both of those conditions (orbit the sun and have an atmosphere) should definitely be called a planet, I did not say that a body that is missing one or the other should not be called a planet. Hence, my assertion is, first of all, not a definition, and secondly, does not exclude Mercury.And like you said yourself, the definition falls apart as soon as you look at Mercury
A coma is not the same as an atmosphere: it is not gravitationally bound to the comet.
And the atmosphere of Pluto is really different? Its only 0.3 Pa surface pressure and it is constantly blown away by the weak solar wind.
True--but it's still gravitationally bound while it's there, and it is replenished by the planet itself. That makes it different from the pseudo-atmosphere of Mercury, which is nothing more than a veil of solar wind.
Then it would be suitable to demote Pluto from planet. Until then I see no reason not to keep it.