Recently Supernova 2006gy was noted as the most luminous ever recorded, with
a total radiated energy of ~10^44 Joules. It was proposed that the progenitor
may have been a massive evolved star similar to eta Carinae, which resides in
our own galaxy at a distance of about 2.3 kpc. eta Carinae appears ready to
detonate. Although it is too distant to pose a serious threat as a normal
supernova, and given its rotation axis is unlikely to produce a Gamma-Ray Burst
oriented toward the Earth, eta Carinae is about 30,000 times nearer than
2006gy, and we re-evaluate it as a potential superluminous supernova. We find
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 ~10^4 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, eta Carinae is unlikely to trigger such effects to any
significant degree.Comment: 19 pages, 2 figures; Revised version as accepted for publication in
Astrobiolog
