X-Ray-luminous Supernovae: Threats to Terrestrial Biospheres

Abstract

The spectacular outbursts of energy associated with supernovae (SNe) have long motivated research into their potentially hazardous effects on Earth and analogous environments. Much of this research has focused primarily on the atmospheric damage associated with the prompt arrival of ionizing photons within days or months of the initial outburst, and the high-energy cosmic rays that arrive thousands of years after the explosion. In this study, we turn the focus to persistent X-ray emission, arising in certain SNe that have interactions with a dense circumstellar medium and observed months and/or years after the initial outburst. The sustained high X-ray luminosity leads to large doses of ionizing radiation out to formidable distances. We assess the threat posed by these X-ray-luminous SNe for Earth-like planetary atmospheres; our results are rooted in the X-ray SN observations from Chandra, Swift-XRT, XMM-Newton, NuSTAR, and others. We find that this threat is particularly acute for SNe showing evidence of strong circumstellar interaction, such as Type IIn explosions, which have significantly larger ranges of influence than previously expected and lethal consequences up to ∼50 pc away. Furthermore, X-ray-bright SNe could pose a substantial and distinct threat to terrestrial biospheres and tighten the Galactic habitable zone. We urge follow-up X-ray observations of interacting SNe for months and years after the explosion to shed light on the physical nature and full-time evolution of the emission and to clarify the danger that these events pose for life in our galaxy and other star-forming regions.

Terrestrial Effects of Nearby Supernovae: Updated Modeling

“…In addition to the long-term CR effects studied here, recent work (Brunton et al 2023) indicates that the effects of SN X-ray emission may be as important as CR impacts, though much shorter lived, even out to 50 pc. SNe as far as 50 pc may therefore present both a short-and long-lived lethal threat for Earth and any Earth-like planet with similar atmospheric conditions.…”

“…These changes occur centuries and longer after any electromagnetic emission is received. Recent work (Brunton et al 2023) indicates that the effects of SN X-ray emission may be as important as CR impacts. However, the two are not coincident in time, with X-ray emission coming in the months to years after the initial outburst and the CR flux becoming significant later.…”

Could a Kilonova Kill: A Threat Assessment

“…SN explosions emit X-rays and gamma radiation and subsequently accelerate lethal cosmic rays, and can be dangerous to life on Earth out to distances around 8-20 pc (Ellis & Schramm 1993;Gehrels et al 2003;Melott & Thomas 2011;Thomas & Yelland 2023). Moreover, if the circumstellar medium (CSM) surrounding a SN progenitor is sufficiently dense, the interaction between the explosion and the CSM can produce lethal X-rays that can kill out to ∼50 pc (Brunton et al 2023). Being located on the axis of a jet from a GRB is potentially far more dangerous, as sGRBs, those with durations under 2 s, can provide a lethal dose of radiation up to ∼200 pc away (Melott & Thomas 2011), increasing to ∼2 kpc for long GRBs (Thomas et al 2005).…”