What Is #11: A Black 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 Brown Dwarfs and White 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. Another type of star is a Black Dwarf. How does a Black Dwarf differ from Brown and White Dwarfs?

Black Dwarfs

A Black Dwarf is a stage of a low mass star, such as the Sun, after the White Dwarf stage. A White Dwarf is the leftover core of a low mass star after it sheds its outer atmospheric layers. Fusion no longer takes place in the star, but it slowly releases the energy it has built up. Eventually all of that energy is released and the object becomes a Black Dwarf. The color black is used to signify the lack of any remaining energy.

The Universe, however, is not old enough for any Black Dwarfs to yet exist!!! At "only" 13.8 billion years old, another "few" billion years are needed for the first Black Dwarf to exist. The oldest White Dwarfs are still releasing energy and are therefore still White Dwarfs. Some estimates suggest another 100 million billion years are needed for the first Black Dwarf to appear. WOW! So don't get excited for finding one yet!