When Betelgeuse goes bad?

Question

Betelgeuse (Alpha Orionis) is a red super giant about 430 LY away, with about 15 the mass of Sol.

I am writing a story and need to know some likely facts:

Assume it went supernova 430 years ago and created a black hole. What effects would be felt at Earth when the light/energy reached us, what would the build-up look like, how long would the night sky be lit by it, what effect would such a large BH have at this range? Etc.

PS If anyone knows coordinates for this star: (XX.XX by XX.XX by XX.XX) that info would also be greatly helpful.

Answer 1

I only want to add that some models for non-recurring gamma ray bursts are a strong burst of radiation from an ordinary supernova relativistically beamed along some rotational axis of symmetry.

In the unlikely event such jets (about 2 degrees wide) are oriented at the Earth, the resulting gamma ray flux even from 430 ly would pretty much sterilize the side facing Betelgeuse during the second or so of the burst's duration. Furthermore, nearly all of the ozone on that side of the planet would be destroyed, removing half of our ozone and resulting in mass extinctions on the other side too.

You can read about the supernova/GRB connection here:
http://chandra.harvard.edu/press/03_releases/press_032403.html
and here
http://en.wikipedia.org/wiki/Gamma_ray_burst#GRB_Jets:__collimated_emission

While Betelgeuse is not a probable progenitor of such an event, our current understanding of GRB sources is still highly speculative, however the association with supernova events for the short duration types is pretty strong so you can't rule it out. Regardless, even correcting for the beaming, you expect about 1 GRB type event per galaxy per 100,000 years, so only about 1 in 1000 SN produces one. So, making the assumption that ANY supernova has the potential to generate one of these events, the odds that Betelgeuse is oriented properly is only 1 in 7000 and that it produces a GRB another one in 1000 for combined odds of 1 in 7 million. Also, chances are GRBs are created by some special circumstance like very rapidly spinning stars (so you get a clear view down the axis at SN collapse) or neutron star mergers or something similarly exotic so this 1 in 7,000,000 chance about Betel doing us in is very very pessimistic.

Answer 2

At the range of Betelgeuse, the effects here on Earth would be a sudden neutrino, gamma and xray pulse (..all non-lethal) and a brightness equal to the full moon. This level of light would fade rather quickly, but still be a noticeable bright spot in the sky anywhere from a week to 10 days.

Betelgeuse is at right ascension 5h 50m and declination +7d 23'