Habitable Zones Around Massive Stars: From the Main Sequence to Supergiants

Abstract

Massive stars dominate the feedback of young stellar populations, yet their ultraviolet fields and winds are often presumed to preclude Earth like habitability. We test this by mapping time dependent habitable zones (HZs) for solar metallicity stars of $0.8$--$120M_{\odot }$. Using rotating and non rotating \textsc{GENEC} tracks, we compute bolometric climate HZ boundaries and impose XUV energy limited escape and wind ram pressure constraints for a dipole-magnetized Earth analogue. The retention limited inner edge is the most restrictive limit. We measure annulus lifetime, longest fixed orbit residence, and maximum dynamically packed terrestrial multiplicity, finding a sharp main-sequence ceiling. A rotating $9M_{\odot }$ star sustains a retention limited HZ for $\sim 30$ Myr at $\sim 70$--$130$ AU, but becomes brief and narrow by $12M_{\odot }$ and disappears by $15M_{\odot }$. Post main-sequence evolution can reopen HZs up to $\sim 25$--$30M_{\odot }$, but only for $\sim 0.03$--$1.5$ Myr at hundreds to $\sim 10^3$ AU, disappearing by $\sim 40M_{\odot }$. Stellar rotation modestly increases habitable lifetimes near the upper main sequence without altering the high mass ceiling. IMF weighting shows that massive stars contribute only $\sim 10^{-4}$ of the habitable planet time budget. Even so, for the fiducial occurrence normalization and if rocky planets form or survive at the required wide separations, they add a few $10^5$ Earth analogues satisfying the adopted criteria to the Milky Way at any instant. Massive star systems do not dominate the Galaxy-wide habitability budget, but may provide short-lived, distinct targets for biosignature searches.

Accepted in ApJ