Am I on the right track with this question?

Question

I am doing a lab on the H-R diagram, and the question is:

"Luminosity" doesn't necessarily mean "brightness". Instead, luminosity refers to the amount of energy that a star is giving off. In the diagram, Betegeuse and Barnard's star are about the same temperature, but Betelgeuse is much more luminous. What is this telling us about the characteristics of these two stars? Name at least 2 characteristics and explain your reasoning"

Now one reason that I want to think has to do with the differences in luminosity is due to the fact that Betelguese is larger and bc of that would most likely emit more luminosity (or energy) and the inverse-square law would play a factor in this? My second characteristic is perhaps the relative distance that each star is.

Is there anyone with some knowledge of astronomy that could help me figure out whether or not I am on the right track with this question? Any help is greatly appreciated. Thanks:)

Answer 1

In your context brightness and luminosity do mean the same thing, and that is the total amount of light given off by the star.

However brightness can sometimes mean surface brightness, which is luminosity per unit area of the star. So a red giant has a low surface brightness, but the large surface area of the star gives a large total luminosity for the star as a whole.

Answer 2

Betegeuse must be giving off more energy which means Betegeuse is more massive then Barnard as massive stars burn thier fuel at a faster rate. Or quote Keplars law.. L = M^3.5



I was thinking distance also, but luminosities alone do not normally suggest a difference in distance.

Good start, I suggest looking for any other Luminousity relationships you can find.

Answer 3

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Answer 4

Spot on!