A star that lived, then died, then lived again, then died for real

Abell 78 is a lovely planetary nebula about 4,500 light years from Earth. Like all of its kind, it was formed when a star similar to the Sun started dying.

It ran out of nuclear fuel in its core, swelled up into a red giant, and started blowing away its gaseous outer layers into a cloud around it. As deeper parts of the star were exposed, a faster wind blew, catching up with and slamming into the older, slower wind. Eventually the core of the star was all that was left: a hot, dense object call...