What Is #17: A Planetary Nebula?

The 'What Is' Series

A couple of months ago I started a new series on this blog titled "What Is". Thus far the focus is on the field of astronomy where we hear all sorts of cool science taking place in space. The goal of this series is to explain the details of different objects we hear about relatively frequently.

Planetary Nebula

A planetary nebula must have something to do with a planet, right? Sorry...wrong! A planetary nebula has nothing do do with a planet, despite the name indicating it might. A nebula is simply a cloud of gas in space. There are different types of nebulae out there. Some are blue in color, others are red, some are dark, etc. Some are caused by new stars forming and others are caused by older stars dying.

Planetary nebula IC 4406 - ESO/J. Richard (CRAL)

A planetary nebula is one of the final stages of a low mass star such as the Sun. As the Sun reaches the end of its life it will expand into a red giant and eventually shed all of its outer layers of gas outward. The shedding of this gas produces a planetary nebula, with the leftover core of the star in the middle. This leftover core is a white dwarf. The shed gas layers are heated to a high temperature and emit their own light for several thousand years before cooling down and becoming no longer visible. 

To conclude, a planetary nebula has nothing do to with a planet, but they do look very impressive in the short time they last. A few thousand years is VERY short in astronomy.