6
Emission
nebulae
•The
red glow is Hydrogen Balmer a (Ha ) emission
•Could
be from hot gas but –
–relative
strength of emission lines not always right
•Can
also get fluorescence:
–UV
photon from bright star boosts electron to high level (or ionizes it)
–Emission
lines created as electron
cascades back down through H energy levels
•The “horse” is a dark cloud in front of the glowing gas.
From our text: Horizons, by Sees