I believe the article that Erik or someone posted outlined the steps that a star 1 or 2 times larger than our sun goes through. Near the end of the process the star once larger than our sun gets compressed down to something the size of the earth and the fusion process has stopped and all that is left is the electron-degenerate matter. Digressing for a second I just recently saw on Nova a guy standing in a library with a ball about the size of a crystal ball and he said.”If this were a nuclei of an atom the electron would be over here", and he walk out of the library for about 2 mile and said, ‘ the electron would be right here. When the former star gets compressed down, due to the very dense core, the electrons also get dragged in towards their nuclei kicking and screaming to the point where it reaches and equilibrium between the core gravity pressures pulling in and the electrons trying to get back to a higher state creating a huge pressure. In this condition the electrons jump out to a higher shell or state and then get pulled back each time giving off energy in the form of heat. The Black Dwarf stage is at this point still theoretical because it takes more that 13.5 billion years for a white dwarf to cool down to the stage of a Black Dwarf. Also keep in mind as has been mentioned but maybe not stressed enough anything the size of this earth only glowing from radiant heat would be very difficult to see even at meager light distances. What we see in M56 and the Helix are in some stage heading to become a White Dwarf but they may not have completed the intire process as yet as outlined in the article. Jim Gibson