>>11771361Very little, other than what we've observed about exoplanets, which is also comparably little. So far our observations have been that our solar system is kind of an oddball, with most system's Jupiter analog being right next to the star and the terrestrial worlds farther out. However it's worth noting in many cases we can only see the (presumably) gas giants anyways, because our current methods of detecting exoplanets can only reliably detect objects about 3x the mass of Earth. It's entirely possible that our Solar System is average and we simply can only see systems that look different from our own due to technical limitations. Other than that, we can look at the metallic content of other star systems, because our own star is incredibly metal rich and it's probable that a metal rich star is necessary for life bearing Earth like planets to form. Earth has a stupid huge core and without it our planet would already be a dead/dying ball of rock like Venus or Mars. Not only that but the presence of a large Moon is also probably a huge component of terrestrial life (interestingly, most likely connected with the creation of Earths huge iron core). We cannot even see exomoons at this point so it's something we cannot study.
tl;dr, current telescopes lack the resolution to regularly observe a large enough portion of other star systems to make an accurate determination of the rarity of Earth-like worlds. So far, from what we can tell, Earth like planets do seem to be very rare, but our understanding is in it's infancy at the moment.
