Superluminous Supernovae: No Threat from η Carinae

Abstract

Recently, Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of ∼10⁴⁴ Joules. It was proposed that the progenitor may have been a massive evolved star similar to η Carinae, which resides in our own Galaxy at a distance of about 2.3 kpc. η Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given that its rotation axis is unlikely to produce a gamma-ray burst oriented toward Earth, η Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We have found that, given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over ∼10⁴ y and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae—endocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered “dangerous” for other reasons. However, due to reddening and extinction by the interstellar medium, η Carinae is unlikely to trigger such effects to any significant degree. Astrobiology 8, 9–16.