I learned something today. http://en.wikipedia.org/wiki/Helium_flash is what I thought was the process that leads to novas, it is not.

That said, from our point of view a helium flash is pretty scary. Of course the Sun is not expected to do this for another 5 billion years.

But according to http://www.whillyard.com/science-pages/our-solar-system/sun-... the Earth is likely to be uninhabitable in about a billion years anyways.