eklhad@ihnet.UUCP (K. A. Dahlke) (04/02/85)
<> While contemplating the universe, a question came to mine. What color are cold neutron stars? They don't have the usual electrons to absorb/reradiate electromagnetic energy. Perhaps they don't interact with light at all (ignoring the gravitational effects). Are they perfectly transparent? however, atomic nuclei do interact with energetic photons, so perhaps neutron stars might interact with light. Perhaps they possess a continuum of energy states, allowing interactions at many wave lengths. Do they absorb everything, becoming black bodies? Perhaps they absorb and reradiate. Are they reflective, like a spherical mirror? Are they transparent like glass, with a huge index of refraction? What a powerful natural lens!! This question is related to the radiation produced by a hot neutron star, although much of this radiation comes from "real" matter on the surface, and companion matter falling thereoninto. Can anyone help me with this all-important question. I would have investigated directly, but the flashlight was too heavy for me. -- Some insipid moronic closing like "my opinions are my own ... " Karl Dahlke ihnp4!ihnet!eklhad
nather@utastro.UUCP (Ed Nather) (04/04/85)
> <> > While contemplating the universe, a question came to mine. Did it have a return address? :-) > What color are cold neutron stars? > They don't have the usual electrons > to absorb/reradiate electromagnetic energy. > > Karl Dahlke ihnp4!ihnet!eklhad They do have on the outside, which is not "pure neutronium" by any means, but is a thin "ocean" of neutron-rich atoms near the iron peak in the curve of binding energy. As such they can radiate into space just like a white dwarf star, only more slowly, because their surface area is so much smaller. Since even the oldest possible white dwarf has not had time to cool off in our young Universe, I'm sure the oldest neutron star is in the same boat, only hotter. They have neutrino cooling to help, but that only really works at very high temperatures. I expect the coolest would still appear to be white to our earth-bound eyeballs, maybe blue-white, but I haven't calculated anything. -- Ed Nather Astronony Dept, U of Texas @ Austin {allegra,ihnp4}!{noao,ut-sally}!utastro!nather