Pluto is an ice-ball, - can it then be a (dwarf)planet?

[vidar]

I think it is an interesting question to ask; whether an ice-ball, like Pluto, can be defined as a planet. If so, isn’t any comet also dwarf planets?<br /><br />According to wikipedia; <br />“Spectroscopic analysis of Pluto's surface reveals it is composed of more than 98 percent nitrogen ice, with traces of methane and carbon monoxide.â€<br />http://en.wikipedia.org/wiki/Pluto#Physical_characteristics<br /><br />Can some astronomers please answer this?<br />

 

[dragon04]

The "definition" of what a planet is or is not has always been at best arbitrary.<br /><br />As far as "dwarf planets" go, comets really don't fit the model. They have highly eccentric orbits, and are vanishingly tiny in comparison to even Pluto.<br /><br />Beyond that, they lose mass due to outgassing every time they complete an orbit around the Sun. Eventually, they evaporate to the point that they will disappear, or break up. Or be "absorbed" by a large body in the case of Shoemaker/Levy 9.<br /><br />Dwarf planets don't suffer that fate. They're in stable orbits that aren't perturbed by anything short of a major gravitational event, so to speak.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[vidar]

“The Hubble Space Telescope places Pluto's density at between 1.8 and 2.1 g/cm³, suggesting its internal composition consists of roughly 50–70 percent rock and 30–50 percent iceâ€<br />http://en.wikipedia.org/wiki/Pluto#Physical_characteristics<br /><br />This means that half the mass of Pluto is ice. Consequently Pluto’s real size is only half of what’s previously assumed, and maybe merely 1/3 the size of our Moon. <br />Pluto seems to me to be just another TNO (Trans Neptunian Object) or KBO (Kuiper Belt Object).<br />http://en.wikipedia.org/wiki/Trans-Neptunian_object<br />http://en.wikipedia.org/wiki/Kuiper_belt<br />

 

[alokmohan]

Poor chap gets demoted all the time.

 

[3488]

I take it that the 1/3 the size of the Moon is volume, not diameter?<br /><br />Anyway a diagram of the Pluto system.<br /><br />P1 = Hydra & P2 = Nix.<br /><br />Are these new figures?<br /><br />Andrew Brown.<br /> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[vidar]

I don’t understand your post.<br /><br />The Forbidden Planet is good though, - and should be remade.<br />My opinion is that Pluto hasn’t ever been any planet, and we shouldn’t maintain that mistake.<br />It chaos any new realization of our planet system.<br />

 

[nexium]

The layer of nitrogen ice may be quite thin, with layers of ammonia ice, methane ice, water ice and carbon dioxide ice below the surface. This still means not much more than 2/3ds rock unless the "rock" is something very low density such as lithium hydride. Density 0.82: There is little reason to expect large amounts of Lithium hydride inside Pluto or any other planet. I suppose several other low density compounds are possible, but not likely. Calcium hydride has a density of 1.9 Neil