Are nebulas cold or warm?

There are both kinds. Optical astronomy found the comparatively hot ones with glowing gases, and some cooler ones that absorbed light from stars behind them (creating dark spectral lines). read more

There are both kinds. Optical astronomy found the comparatively hot ones with glowing gases, and some cooler ones that absorbed light from stars behind them (creating dark spectral lines). Infrared and submillimeter observations have turned up a lot more cool and cold ones (Google "Boomerang Nebula"). read more

The glow of the Eagle nebula is generated by the massive O- and B-type stars that populate its centre. Many times more massive than the Sun, these enormous stars burn hot and fast, ejecting ionising radiation and stellar wind into the heart of the nebula, sending shock waves through the cloud. read more