Cosmic-Ray Bath in a Past Supernova Gives Birth to Earth-Like Planets

TL;DR

This paper proposes a new mechanism where cosmic-ray nucleosynthesis in supernova shockwaves can produce the short-lived radionuclides necessary for Earth-like planet formation, making such planets more common.

Contribution

The study introduces the 'immersion' mechanism, showing how supernova shockwaves can deliver SLRs to protoplanetary disks without destruction, explaining Earth's radionuclide abundance.

Findings

Supernova shockwaves can produce SLRs via cosmic-ray nucleosynthesis.

Stars in clusters likely experience nearby supernovae, supporting the mechanism.

Earth-like planet formation may be more common than previously believed.

Abstract

A key question in astronomy is how ubiquitous Earth-like rocky planets are. The formation of terrestrial planets in our solar system was strongly influenced by the radioactive decay heat of short-lived radionuclides (SLRs), particularly $^{26}$Al, likely delivered from nearby supernovae. However, current models struggle to reproduce the abundance of SLRs inferred from meteorite analysis without destroying the protosolar disk. We propose the `immersion' mechanism, where cosmic-ray nucleosynthesis in a supernova shockwave reproduces estimated SLR abundances at a supernova distance ($\sim$1 pc), preserving the disk. We estimate that solar-mass stars in star clusters typically experience at least one such supernova within 1 pc, supporting the feasibility of this scenario. This suggests solar-system-like SLR abundances and terrestrial planet formation are more common than previously thought.