The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths

TL;DR

This paper constructs the minimum-mass extrasolar nebula (MMEN) to explore in-situ formation of close-in super-Earths, demonstrating it as a fast, efficient process that matches observed planetary properties without requiring migration.

Contribution

It introduces the MMEN as a new model for in-situ formation of super-Earths, providing a framework consistent with observed planetary characteristics.

Findings

In-situ formation in the MMEN is rapid and efficient.

The model reproduces observed gas-to-rock ratios.

Predictions for observable properties are discussed.

Abstract

Close-in super-Earths, with radii R = 2-5 R_Earth and orbital periods P < 100 days, orbit more than half, and perhaps nearly all Sun-like stars in the universe. We use this omnipresent population to construct the minimum-mass extrasolar nebula (MMEN), the circumstellar disk of solar-composition solids and gas from which such planets formed, if they formed near their current locations and did not migrate. In a series of back-of-the-envelope calculations, we demonstrate how in-situ formation in the MMEN is fast, efficient, and can reproduce many of the observed properties of close-in super-Earths, including their gas-to-rock fractions. Testable predictions are discussed.