In-Situ Formation of Close-In Super-Earths

An interesting article about the formation of close in super-earths without using the migration model.

Here the paper: http://arxiv.org/abs/1211.1673

More at the systemic blog, interesting read. I wonder how likely the formation of HZ planets is if this model is correct.

Quote :

Could it be that the huge population of super-Earths formed right where they are observed? If that’s the case, it makes life simpler, and it implies that the template we’re after is the Minimum Mass Extrasolar Nebula (MMEN), which can be defined by grinding up the planets that have been observed by Kepler, and which is not all that different from what one gets if one simply takes the MMSN and runs it all the way into the dust sublimation boundary at ~0.05 AU.

Leads to the question of how to get from the MMEN to the MMSN - if the main difference is the region between ~0.05 AU and ~0.5 AU was cleared out in our solar system what is the reason for that happening?

Testing In Situ Assembly with the Kepler Planet Candidate Sample
http://arxiv.org/abs/1301.7431

Matches the relative frequencies of multiples pretty well but seems to underpredict the number of single-transit systems... post-formation dynamics perhaps?

The Formation of Systems with Tightly-packed Inner Planets (STIPs) via Aerodynamic Drift
http://arxiv.org/abs/1306.0566

Further exploration of in-situ formation of close-in planets, and attempting to place the solar system into this picture.

Quote :

Here, we suggest that, instead of a Grand Tack among the giant planets, solids aerodynamically drifted inward, concentrated due to decreasing terminal drift speeds, and formed a series of embryos. This could, depending on the disk and cloud properties, form a relatively compact inner disk of solids with a depleted region near the current asteroid belt. Dynamical instability of the nascent inner Solar System could lead to the current spacings and the low mass of Mars, as envisaged in the Hansen (2009) calculations. There are at least two interpretations of this scenario. (1) The Solar System is on the low-mass, less tightly-packed tail of a distribution of inner planetary systems. (2) The inner Solar System was once more massive, with a possible lost super-Earth at short orbital periods. In either case, in this context, the Solar System owes the formation of the terrestrial planets to aerodynamic drift. Furthermore, this suggests that STIPs are likely to have a lower-mass, exterior planet, even if not yet detected. TTVs may reveal these planets.