Exploring plausible formation scenarios for the planet candidate orbiting Proxima Centauri

Understand

We present a study of four different formation scenarios that may be able to explain the origin of the recently announced planet (`Proxima b') orbiting Proxima Centauri.

• The aim is to examine how the formation scenarios differ in their predictions for the multiplicity of the Proxima system, the water/volatile content of Proxima b and its orbital eccentricity, so that these can be tested by future observations.
• A scenario of in situ formation via giant impacts from a locally enhanced disc of planetary embryos/planetesimals predicts that Proxima b will be in a multiplanet system with a measurably finite eccentricity.
• Assuming that the local solid enhancement needed to form a Proxima b analogue arises because of the inwards drift of solids in the form of small planetesimals/boulders, this scenario also results in Proxima b analogues being only moderately endowed with water/volatiles.