1212.1482 (Jarrett L. Johnson et al.)

Formation of the first planets via gravitational instability: constraints from the cosmic microwave background    [PDF]

Jarrett L. Johnson, Hui Li

We estimate the maximum temperature at which planets can form via gravitational instability (GI) in the outskirts of early circumstellar disks. We show that due to the temperature floor set by the cosmic microwave background, there is a maximum distance from their host stars beyond which gas giants cannot form via GI, which decreases with their present-day age. We compile the available data on planetary systems and find that they are broadly consistent with this prediction. We conclude that while the first terrestrial planets likely formed via core accretion, the first gas giants may have formed via GI within a few astronomical units of their host stars.

View original: http://arxiv.org/abs/1212.1482