Pathways to Astronomy

Stephen E. Schneider

Chapter 58 The H-R Diagram - all with Video Answers

Educators

Chapter Questions

Problem 1

Estimate the luminosity and temperature of the star Acrux by examining its vertical and horizontal position in the H-R diagram (Figure 58.3 ). (You should make an estimate of these values by interpolating between the values marked on each axis.) Using the values you estimated, determine the size of Acrux as compared to the Sun, using the Stefan-Boltzmann law (Unit 57 ).

Sarah Mccrumb

Numerade Educator

08:36

Problem 2

Alnitak is the brightest O-class star in the night sky, located at the eastern end of Orion's belt. Proxima Centauri is the near-
est M-class main-sequence star. Estimate the luminosities and temperatures of these two stars from their positions on the H-R diagram (Figure 58.3 ) as in the previous problem. Calculate the ratio of their sizes using the Stefan-Boltzmann law.

Matthew Miranda

Numerade Educator

00:33

Problem 2

From your data in problem $2,$ use the mass-luminosity relationship to estimate the ratio of masses of these two stars.

Farhanul Hasan

Numerade Educator

05:18

Problem 4

If a main-sequence star has a luminosity of $3000 L_{\odot}$, what is its mass in relation to the Sun's?

Matthew Miranda

Numerade Educator

05:18

Problem 5

Estimate the luminosity of a main-sequence star that has a mass twice the Sun's. By what factor is such a star brighter than the Sun?

Matthew Miranda

Numerade Educator

05:18

Problem 6

How massive would a main-sequence star need to be, to be 100 times brighter than the Sun?

Matthew Miranda

Numerade Educator

04:12

Problem 7

Use the mass-luminosity relationship and the StefanBoltzmann equation from Unit 57 to work out the surface temperature of a star with half the radius of the Sun and oneeighth the mass.

Sarah Mccrumb

Numerade Educator