Which of the following quantities is NOT necessary to observe in order to construct an HR diagram of a system of stars?
A) distance to each star
B) mass of each star
C) color of each star
D) brightness of each star

Question

Quizplus · Accepted Answer

Mass of each star is not necessary to construct an HR diagram. The HR diagram is created by plotting the color and brightness of each star, which can be obtained through observation, and distance can be estimated using various methods, such as parallax. Mass can be inferred from the position on the diagram, but it is not a necessary observation.

Which of the Following Quantities Is NOT Necessary to Observe