The Pulsar Planets: A Test Case of Terrestrial Planet Assembly

TL;DR

This paper models the formation of planets around pulsar B1257+12, exploring different disk scenarios and their ability to reproduce observed planetary characteristics, highlighting challenges in matching system compactness.

Contribution

It introduces detailed simulations of pulsar planet assembly considering various disk compositions and dynamics, providing insights into plausible formation pathways.

Findings

Models with low angular momentum disks fit observations better.

Solar composition disks are more likely than heavy-element disks.

Simulations reproduce planetary masses and eccentricities but struggle with system compactness.

Abstract

We model the assembly of planets from planetary embryos under the conditions suggested by various scenarios for the formation of the planetary system around the millisecond pulsar B1257+12. We find that the most likely models fall at the low angular momentum end of the proposed range. Models that invoke supernova fallback produce such disks, although we find that a solar composition disk produces a more likely evolution than one composed primarily of heavy elements. Furthermore, we find that dust sedimentation must occur rapidly as the disk cools, in order that the solid material be confined to a sufficiently narrow range of radii. A quantitative comparison between the observations and the best-fit models shows that the simulations can reproduce the observed eccentricities and masses, but have difficulty reproducing the compactness of the pulsar planet system. Finally, we examine the results of similar studies of solar system terrestrial planet accumulation and discuss what can be learned from the comparison.