What Is #16: A Green Dwarf?

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.

Stars

I have recently covered Black Dwarfs, Brown Dwarfs, White Dwarfs, Red Dwarfs, and Blue Dwarfs. Brown Dwarfs are objects that were not quite large enough to fuse hydrogen, so they never reached full star status. White Dwarfs are the final stage of a low mass star such as the Sun. After these low mass stars shed away their outer layers, the stellar core leftover is called a White Dwarf. Black Dwarfs do not yet exist in the Universe, but eventually White Dwarfs will finally emit all of their energy, leaving behind a leftover core that no longer releases energy. This leftover core will be called a Black Dwarf. Red Dwarfs are the very low mass Main Sequence stars fusing hydrogen into helium in their cores. Blue Dwarfs don't yet exist, but will once Red Dwarfs in the Universe are old enough to exhaust their hydrogen supply. Are there Green Dwarfs and if so, what are they?

Green Dwarfs

This may be a surprise to you, but guess what? There are no Green Dwarfs in astronomy! In fact, if you do a search for Green Dwarfs, you'll find some book titles and a type of tomato plant, but nothing on stars. In fact, there are no green stars. There are stars that emit more green light than the other colors in the visible spectrum, so technically you could call them green stars. However, these 'green' stars also emit a lot of red, blue, yellow, etc. light, which all mixes together as 'white' light. White light is a combination of all colors on the visible part of the electromagnetic spectrum. Therefore there are no green stars and therefore no Green Dwarfs!