Is the red supergiant Betelgeuse about to go supernova, giving Earth a second sun and half of its inhabitants a nasty burn? The short answer according to astronomer Phil Plait, is that yes, Betelgeuse could go tomorrow, but if it did it's greatest impact on the Earth would be to give us a new celestial phenomenon as bright as a full moon. It's too far away to do us any real harm.
I, for one, would love to see a nebula that brilliant in the night sky. Comets are nifty, but a naked-eye nebula as bright as the moon? That's a once a thousand life time opportunity.