<p><font size="3">Again, guys-- this is why I posted the question in the first place.</font></p><p><font size="3"> How do we really know that these objects aren't Mega Terrestrial planets? Is the catch phrase "Hot Jupiters" making us assume that they HAVE to be gas giants? It would certainly be logical to conclude that some of them certainly are. A recent planetary transit of one of these puppies seems to confirmed that. But as far as most of them are concerned, all we have is a mass range and an orbital radius calulated by the pull that these exoplanets have on their parent star, and that is it. We do not have a density as of yet. (Stick around though, because, excitingly, WE WILL!) </font></p><p><font size="3"> The phrase, "Using our solar system as a model, scientists have determined that such giant planets can only be jupiter-like planets." is the crux of my question. What article, book, website did you see this? I doubt if they have-- or can at this point-- determine that. They would need a transit on ALL of them using existing tools. I've never seen or read ANY info on the density of these big ol' planets, except for the one's aready mentioned. That doesn't mean that you haven't, of course. Please enlighten all of us if it's true. I love to be enlightened, that also why I asked the question. If there is another way to calculate the density that is new that you've heard about, I'd really like to hear about that too!</font></p><p><font size="3"> I also don't like to draw too many conclusions from our Solar System because it's only a model of one. It seems to be true that there are many types of solar systems out there. At this time, we certainly have the ability to find the ones with huge planets orbiting very close to the parent star and a few other types. The book on Solar System Types can't even get through the first few pages of the Introduction yet!</font></p><p><font size="3"> Also, if some of these are indeed HUGE terrestrail planets, they would show the same gravitational tug as a hot Jupiter AND have a smaller radii. That is obvious because they are rocky and not made up of gas. That's my point. That's why a planet like Jupiter can have well over half of the mass in our Solar System (excluding the Sun, of course) and only have a "surface" gravity of 2.4-ish that of Earth. Or, in other words, a rocky world 10 to 100 times more massive than Earth WOULD tug on a star EXACTLY like a Hot Jupiter. After all, mass is mass. It's like the old joke of what weighs more: a pound of nails or a pound of feathers. A pound is a pound regardless of the "stuff" within it, right?</font></p><p><font size="3"> Without getting too mathematical-- I know you would have to calculate the difference in density-- that kind of "Earth" would be much smaller than a real "Hot Jupiter," but have the same mass. I think us novices are on the right track when we were talking about just how much metals we could expect to find in these systems. If it turns out that my question is just another wrong assumption, it would probably be because of that. It seems to me that until we start to get a spectra back from these worlds, and I believe we are starting to, we can make no conclusion on if they are made up of mainly metals or gases.</font></p><p><font size="3"> Remember, I'm not really even talking about Earth-type planets here, and that's the problem, I suppose, with using this type of phrasing. These would be terrestrial, and rocky, but nothing like our Earth. The surface gravity of these bad boys would be crushing! Their spectra might even mimic a gas giant by having a lot of hydrogen and helium (H, He) in the atmospheres. They would have the surface gravity to hold onto it. I don't know how large a potentially huge terrestrial planet would have to be to do this, but even the Earth itself is still leaking extremely small amounts of these gases into space eventhough 99.9.....9 % of our H and He is long gone.</font></p><p><font size="3"> As far as whether real "Hot Jupiter's" have metal cores or not is easily calculated once we get densities for them. The gas giants we know best in our solar system cetainly do because we know their densities. I wonder if a purely H and He "Hot Jupiter" could survive in a close orbit of a star. I guess it would depend on how active the star is, just how close, the masses involved, etc. It would be intersesting to start finding mainly carbon gas giants out there. But let's face it, any thing heavier that H and He in these gas giants are going to sink to the center and be part of the core, (unless something REALLY weird is going on.) I'd have to conclude from that that most gas giants would have to have cores made up of what the Astronomy community calls "the metals." Also just remember that the temperatures inside these extremely large gas giants would bring any "rocky stuff" heated down into their individual elements. The pressures involved would indeed make them solid or "metalically liquid." Jupiter supposedly has metallic H and He as you go down towards the core. There is also another theory floating around that if Jupiter has a mainly carbon core that at such pressures would turn it into a diamond the size of Earth. </font></p><p><font size="3"> Again, I appreciate all of your feedback!!!!!!!!!! It all makes you wonder, huh?</font></p><p> </p><p><font size="3">Thanks again you guys, Aretis</font></p> <div class="Discussion_UserSignature"> <p><font size="4" color="#0000ff"><strong>Aretis</strong></font></p> </div>
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