Originally posted by sonhouse
What amazes me is the amount of Jovian planets with thick atmospheres like Jupiter but are a few million miles from their sun.
Those planets are roasting and it must be because of the immense gravity they retain an atmosphere, with temps in the thousands of degrees C some of them.
It's really curious why so many stars have such close ordered Jovian cold but thrown in by some other body, passing star? Another Jovian planet getting too close?
there are a number of posited explanations.
one of which is friction from the planetary disc dust cloud before the relevant star kicks into gear and blasts it away.
But there are a number of alternatives.
However you have to be careful extrapolating too much at this stage, as there is a significant selection effect in your detection methods.
The dopplar shift method of planet detection, that looks for a tiny wobble in the parent star is far more likely to detect large objects and
objects with short period orbits.
Hot Jupiter's have both short orbit periods and are massive thus making them the easiest and fastest planets to detect.
Stellar dimming technique is better for detecting small stuff, but the downside is that the planets in question have to orbit in a plane that
means they pass between us and their parent star.
However detecting a gas giant orbiting in a stars habitable zone is very promising for life, as it is (based on all the gas giants in our solar
system) very likely to have multiple moons, which could potentially be suitable for life.
EDIT: Also if I recall there is another option that suggests the hot Jupiter got into gravity resonance with the inner planets and
threw them out the solar system while it moved inwards....