Could a planet the size of Jupiter actually be made out of solid rock?
Cool question. No. The gravity would not cause it to “implode” but the interior would get hot enough to have a molten mantle. Perhaps there would even be a region where the rocky material was gaseous. Just taking my best guess. It is believed that even though the core of Jupiter is at 30,000 degrees, it is made of solid rock and metal with a shell of water ice around it. Weird, huh?. Your all-rock planet (or mostly rock) of that size is unlikely, unless it is pretty close to the star it formed around, in which case, your capture hypothesis is no longer applicable. It is also possible that there may be rogue interstellar planets which were pulled away from their parent star by another star. If such a planet passed by a very massive star, it could fall into a highly elliptical orbit. It would almost certainly not be close to circular. For the record, there is no such planet in orbit around the sun. You know, there are astronomers who are experts in planetary models and this is worth aski
