No, I didn't mention that. Jerry was the one who posted about the visibility of white dwarfs in a cataclysmic variable system, not Bishop. I was attempting to distance that from Bishop and try to underline the differences. In my post, Bishop's comments were in quotes, mine were not. Sorry for the apparent confusion. Also, I need to research this, but I'm not sure that planetary nebula are illuminated by the central star, but by the expelled material colliding with material ejected previously. These are glowing, ionized nebula, not merely reflection nebula. On Sun, Jan 25, 2009 at 8:05 PM, <zaurak@digis.net> wrote:
You also mention that he is talking about white dwarfs from cataclysmic double stars. Perhaps in the case of planetary nebula (I believe most of these are not from cataclysmic doubles), that there is nothing to see until the "life" of White Dwarf is turned on, to illuminate the gases expelled from the red giant. Simply the intermediate period is before the nebula is visible. Again, I imagine most white dwarfs are not the product of double star systems gone wrong.