[Rockhounds] Supernova and Mass Extinctions

[Paul]

Distance at which supernova would spark mass
extinctions on Earth, University of Kansas, May 11, 2017
https://www.sciencedaily.com/releases/2017/05/170511115935.htm
http://news.ku.edu/2017/05/08/research-increases-distance-which-supernova-would-spark-mass-extinctions-earth

What’s a safe distance between us and a supernova?
by EarthSky, May 7, 2017
http://earthsky.org/astronomy-essentials/supernove-distance

Yours,

Paul H.