Kirchoff’s Laws
The brightness of lines from a gas depend upon its temperature.
A cool cloud in front of a hot blackbody.
- Lines from the cloud are darker than the blackbody.
- Dark lines in appear in the blackbody spectrum
A hot cloud in front of a cool blackbody
- Lines from the cloud are brighter than the blackbody
- Bright lines appear in the blackbody spectrum
By identifying the lines, you can tell what the cloud is made of and what temperature it is!