Question #143632. Asked by chabenao1.
Last updated Dec 21 2016.
Originally posted Dec 21 2016 2:37 AM.
...at distance of around 400 light years, is the closest planetary nebula to the Earth. It formed when a dying star threw off its outer layers which are gradually expanding into space. They are called planetary nebulae because astronomers originally believed they were new planets, due to their often spherical shapes. The Helix Nebula is around 100 times more distant than the nearest stars (excluding the Sun).