How Do Rocky Planets like super earths Really Form in our Milky Way galaxy

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"A new theory for how rocky planets form could explain the origin of so-called "super-Earths"—a class of exoplanets a few times more massive than the Earth that are the most abundant type of planet in the galaxy.

Further, it could explain why super-Earths within a single planetary system often wind up looking strangely similar in size, as though each system were only capable of producing a single kind of planet. ...
In our solar system, there are two distinct types of planets: the smaller rocky inner planets closest to the sun and the outer larger water- and hydrogen-rich gas giants that are farther from the sun. In an earlier study ... this dichotomy led ... to suggest that planet formation in our solar system occurred in two distinct rings in the protoplanetary disk: an inner one where the small rocky planets formed and an outer one for the more massive icy planets (two of which—Jupiter and Saturn—later grew into gas giants). ..."

From the abstract:

"The formation of super-Earths, the most abundant planets in the Galaxy, remains elusive. These planets have masses that typically exceed that of the Earth by a factor of a few, appear to be predominantly rocky, although often surrounded by H/He atmospheres, and frequently occur in multiples. Moreover, planets that encircle the same star tend to have similar masses and radii, whereas those belonging to different systems exhibit remarkable overall diversity. Here we advance a theoretical picture for rocky planet formation that satisfies the aforementioned constraints: building upon recent work, which has demonstrated that planetesimals can form rapidly at discrete locations in the disk, we propose that super-Earths originate inside rings of silicate-rich planetesimals at approximately ~1 au. Within the context of this picture, we show that planets grow primarily through pairwise collisions among rocky planetesimals until they achieve terminal masses that are regulated by isolation and orbital migration. We quantify our model with numerical simulations and demonstrate that our synthetic planetary systems bear a close resemblance to compact, multi-resonant progenitors of the observed population of short-period extrasolar planets."

How Do Rocky Planets Really Form? | www.caltech.edu Scientists unveil a unified theory for rocky planet formation

Formation of rocky super-earths from a narrow ring of planetesimals (no public access, however here is the preprint arxiv article)