Formation of gas and ice giant planets

The only presently known example of a planetary system containing a terrestrial planet in the habitable zone of a main sequence star is the Solar System. If the Solar System's giant planets formed by the generally assumed mechanism of core accretion, the Solar System probably formed in a relatively long-lived protoplanetary disk in a quiescent region of star formation, such as in the Taurus molecular cloud. However, if the giant planets formed by the more radical disk instability mechanism, then the Solar System would have formed In a region of high mass star formation, similar to the Orion Nebula Cluster or the Carina Nebula. In the latter case, the number of extrasolar planetary systems strongly resembling our own is likely to be significantly larger than in the former case with important implications for the design of Darwin/TPF.