I don't know, I think the lion's share of the emission is from the ionization, not reflection. The dwarf is intrinsically very dim. But what could energize the OIII from a merely thermally radiating body? See, this is what makes me think that during the brief lifetime of the nebula itself, the central star has not become a true white dwarf. I think it's still sputtering the last dregs of fusion- from matierial on it's surface, not core- before settling down to true "white dwarf" status. And much of the ionization is due to the nebula material colliding with older material previously expelled. It doesn't always happen just once. I think lecturers don't make the distinction because it's a brief, transitory phase, and their lecturing to a general audience, not graduate students. And of course, I could be completely wrong! Invoking Ocham's razor, I'm probably wrong, lol. 2009/1/25 Kim <kimharch@cut.net>
Like you, Chuck, I haven't had the time to do any immediate research, but I seem to recall that the radiation energy (what radiation I can't say - I'm no physicist, either) that causes the pn to be visible is ionizing radiation causing the pn to emit light from O3 emissions - therefore, not merely a reflection phenomena, but I'm certain that could also be a component.
Kim
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Sunday, January 25, 2009 8:18 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] White dwarfs and YOU
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.
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