Question

which two characteristics are used to classify stars on the hertzsprung - russell diagram?
○ size and density
○ density and composition
○ composition and temperature
○ temperature and absolute brightness

Explanation:

The Hertzsprung - Russell diagram classifies stars based on their temperature and absolute brightness. Temperature is related to the color of the star and absolute brightness is an intrinsic property representing how bright a star truly is.

Answer:

temperature and absolute brightness