How might this density affect the appearance of the spectrum?  Why? In
view of the size and lack of energy source for the star, would it have
a
low or a high luminosity?  Why?

http://www.astro.washington.edu/labs/clearinghouse/labs/Leo/distleo.html
"Distances to Stars in Leo"

"For a given element, supergiant stars will have narrow lines and
dwarf stars will have broad lines."

"Note that the lines of the white dwarf are so broad that they are
smeared out."

http://www.ifa.hawaii.edu/~acowie/class99b/class_15.html "Astronomy
110
Fall, 1999 Section 5 Class 15 Tuesday, October 12, 1999"

"The larger the surface gravity the broader the lines."

http://earth.ast.smith.edu/courses/ast100/review2.htm "AST 100 Review
II."

Therefore, since white dwarfs are much denser "Average density: 106
gm/cm3," they have greater surface gravity, which broadens the lines
of its spectrum.

"Dwarfs: same temperature, lower luminosity" than main sequence stars

"Low mass stars: He fusion to C,O core => Expulsion of atmosphere
(planetary nebula) => exposed C,O core (white dwarf)"

http://www.astronomynotes.com/evolutn/s2.htm# "Stellar Evolution" by
Nick Strobel

"...star's luminosity increases with mass as (the star's mass)p"

Therefore, the white dwarf has a lower luminosity because it has much
less mass.

Sincerely,

Wonko

Terrific! Thanks!