प्लेनेटरी Nebula

My definition of a planetary nebula is firstly one I can see with my beady eye if I stretch lengthways across the ridgeway in the dark matter(found easily by going directly north when England is the right way up on the globe) and concentrate at least. I can't be thinking about cricket or any some such nonsense and slowly but surely if I am respectful with my attention, I will see an emission nebula consisting of an expanding glowing shell of ionized gas and plasma ejected during the asymptotic giant branch phase of certain types of stars late in their life.

To give you some history from the wickedpedia, the name originated with their first discovery in the 18th century because of their similarity in appearance to giant planets (and scizzletops) when viewed through small optical telescopes (or along the ridgeway), and is otherwise unrelated to the planets of the solar system. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.

At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the remaining core of the star shines brightly and is very hot. The ultraviolet radiation emitted by this core ionizes the ejected outer layers of the star which radiate as a planetary nebula.

I know a ballerina who likes the stars and he also works part-time for NASA in their cultural space collaboration thing bringing together artists and astronauts project and he gives astronauts dance tips.