5
votes
2answers
85 views

How hot is aurora?

Has anyone done research on how hot aurora is? I mean if it is plasma it should be hot and since it is emitting mostly green light due to nitrogen (~78%) in the air, could it then be considered that ...
7
votes
1answer
201 views

How would a physicist measure temperature of molten metals in 1850-1920s?

How would a physicist measure temperature of molten metals in 1850-1920s? What equipment would be used?
8
votes
3answers
375 views

Significance of letters in Hertzsprung-Russell (H-R) diagram

The Hertzsprung-Russell diagram that categorizes star types uses the letter codes O, B, A, F, G, K, and M to indicate a star's temperature/color. Hottest (blue) is O and coolest (red) is M. What do ...