<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Astrodelugeologist</i>
<br />In your article, "What Happened to Pluto?" in the September 2006 issue of <i>Meta Research Bulletin</i> recently posted on the Meta Research website, you state that it is likely that Planet X was a gaseous planet. Basically, I would like to hear your reasoning and supporting evidence for this statement. Why do you think that Planet X was probably a gaseous planet? Do you have a general theory to determine which planets would be gaseous and which would be terrestrial?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The "general theory" is simple and easy to understand. In fission theory, all planets start life as gaseous blobs fissioned from the Sun. As such, they are made primarily of hydrogen and helium (99%), with less than 1% in "metals" (defined as astronomers do as "everything heavier than hydrogen and helium".
Before the planet cools, the H and He molecules have a rather high mean molecular speed. If the planet has enough mass, that presents no problem because escape velocity is much higher. So almost all hydrogen and helium are retained, and the planet remains a gas giant. But if the planet has a small total mass, escape velocity will be smaller than the mean speed of the lightest molecules. So almost all the hydrogen and helium will escape, and the planet will cool and condense the remaining metals and become a terrestrial planet.
While the concept is simple, it has yet to be developed into a quantitative model. Contracting stars in their early T-Tauri stage will be huge and amorphous. So when outer planets fission, the gas balls start out cool and with low molecular speeds. So planets can remain gas giants down to smaller masses. By contrast, when the Sun has contracted inside some radius and heated up, fissioning makes ever smaller planets with ever higher molecular speeds, so most planets must become terrestrial type.
The problem, of course, is that these qualitative concepts have not yet been developed quantitatively. So we are left to guess where the transition borders lie, both in the inner and outer solar system. And my "best guess" of the border locations has likewise changed over time.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">In your 1997 <i>MRB</i> article, "The Original Solar System", you hypothesize that Planet X was about 3 times as massive as the Earth. Isn't this rather small for a gaseous planet?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Coolness of the protoplanet allows smaller bodies to remain gaseous. But I am still just guessing about the planet's chemical state here.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Also, if I recall correctly, in <i>Dark Matter,...</i>, you argue that Planets V and K were solid, terrestrial planets, and in "The Original Solar System", you hypothesize that these two planets were 8 and 10 times more massive than Earth, respectively. Aren't these rather large for terrestrial planets?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">These are in the inner transition zone where larger terrestrial planets can form because their original high temperatures assures the escape of more hydrogen and helium right at the outset.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Are there upper and lower mass limits for gaseous and terrestrial planets, or are my assumptions regarding planet masses too narrow, being based only on the extant planets of the Solar System?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">As I indicated, the theory has not yet been quantified sufficiently. Moreover, all mass estimates for exploded planets are just guesses. In a coming MRB article (hopefully, our 2007 March 15 issue), I have developed a quantitative way to estimate these masses. This is a lot less arbitrary than gesswork, but still rests on a number of assumptions.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If Planets T and X were twins, and Planet X was gaseous, would this require that Planet T be gaseous as well?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The mass difference between twin pairs is a mere 20%, which is unlikely to bracket a critical transition mass. But it could.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Is there any possible scenario in which one planet could be gaseous and its twin terrestrial?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes. In this critical zone, one planet would retain helium and the other not retain it. So a rare class of "helium planets" is predicted.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Finally, are your conjectured Planets A and B gaseous or terrestrial?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The "late heavy bombardment" was so massive and destructive that I'm thinking that the parent bodies must have been very massive too, and therefore gaseous. Impacts blast craters by explosion of the high-speed impactor, not by excavation. So even large balls of cooled gas should be able to blast craters of significant size. However, remaining in a coherent gas ball long enough to travel many astronomical units, rather than dissipating, is a step that can be challenged. So perhaps the impactors were exploded moons of gas giant planets.
As you see, there are still many unknows in the fission scenario. But there are more in the standard model. As MRB subscribers read in our June issue, we are not even sure that the Sun is in a gaseous state, as opposed to a condensed ("liquid") state. So all of stellar evolution theory rests on slippery assumptions. We still have so much to learn. -|Tom|-
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