A supernova or hypernova are definite possibilities
The radiation from a nearby one of those would end life on Earth quite quickly.
http://imagine.gsfc.nasa.gov/docs/features/news/20may99.html
Keep an eye on Betelgeuse, a red supergiant sun a mere 472 light years
away located in Orion. Some winter we may get a new Star....
http://en.wikipedia.org/wiki/Betelgeuse
