Another "Just Right" Element in our Solar System
I have another entry from Sky & Telescope magazine that adds further evidence that the Privileged Planet is More Privileged Than We Thought. In a news item entitled, "Our 'Goldilocks' Solar System," the magazine discusses a new scientific discovery regarding planet-building necessities.
Not too hot, not too cold. . . that's just part of what it takes to make a nice world like ours. Recent planet-building computations have found a new constraint. The protoplanetary disk of gas and dust that spawns a planetary system must be neither too massive nor too sparse.
If it's too massive, may giant planets will form. They interact and pull each other's orbits into chaos, expelling or wrecking any smaller worlds. Too little mass, and big planets wouldn't form at all. Our own solar system, which does have giant planets but in safe, distant, nearly round orbits, appears to be an unusual, right-on-the-balance case.
This in turn suggests that having giant planets in round orbits is somehow important for a terrestrial planet to develop intelligent life. If this were not so, we would be unlikely to find ourselves in a system of this unusual type.