Transcript: The Doppler Effect is the shift of wavelength or frequency of a source of waves due to the motion of that source of waves. Doppler Effect is most familiar in terms of sound waves. As a source of sound, such as a siren, approaches you, the pitch or frequency increases. As it moves...

Transcript: German physicist Gustav Kirchhoff experimented with hot gases in the laboratory in the mid-nineteenth century and deduced three laws of radiation that apply to all astronomical objects in space. The first is that a hot gas or sufficiently hot solid will emit with a continuous...

Transcript: When a hot object like a star is surrounded by a cooler layer of gas or has an intervening cool material we see an absorption spectrum. Always they’re at the smooth thermal radiation reflecting the temperature of the object itself, but in the case of an outer or intervening cool...