how long would betelgeuse light up the night sky when it explodes?
red supergiant, few hundred light years away.
Factor it's distance and the speed of light, and you'll be able to roughly determine how long we would see it. After that, buh-bye...
We are seeing it like it was hundreds of years ago, if it blew today none of us would live to see it. The light wouldn't reach the earth for hundreds of years. It may be gone already, and we just don't know it.It won't destroy the earth.