These questions are about the Hertzsprung–Russell (HR) diagram,
and the measurements needed to create it.

Q1-2. To find distances to nearby stars, the method of stellar parallax is used, measuring the shift in position as shown in the diagram below:

parallax to star diagram

The distance to the star (in parsecs) is given by:

$ \text{d (parsecs)} = {1 \over{\text{parallax angle p (seconds of arc)}}} $

1. Which angle A to D in the diagram above is the required parallax angle p?

2. The star is being observed from 2 positions, shown as X and Y in the diagram. These points are...

  • A. two points on opposite sides of the equator
  • B. the Earth and a space telescope
  • C. the Earth's position on opposite sides of its orbit around the Sun
  • D. any of the above

3. Once the distance to a star is known, the luminosity can be calculated by measuring the...

  • A. surface area
  • B. apparent brightness
  • C. surface temperature
  • D. peak wavelength

4. A star of radius R has a luminosity L and surface temperature T. Another star has half the surface temperature but a luminosity of ¼L. This means the radius of the second star is:

  • A. 4R
  • B. 2R
  • C. ½R
  • D. ¼R

5+6: The diagram below shows the Hertzsprung-Russell diagram, with three regions of stars indicated:

HR diagram
5. What type of stars are in region 1?

A). red giants
B). white dwarfs
C). red dwarfs
D). main sequence stars

6. What type of stars are in region 2 and 3?

Region 2 Region 3
A
 main sequence white dwarfs
B
 main sequence red giants
C
 white dwarfs red giants
D
 white dwarfs main sequence

7 Which of these HR diagrams shows the correct location of supergiants?

HR diagram supergiants with 4 options

8. Which of these diagrams correctly shows lines of equal radius?

HR diagram lines of equal radius with 4 options

9. Which of these diagrams shows the approximate location of the 'instability strip' - with unstable variable stars?

HR diagram instabilty strip with 4 options
10. The HR diagram here shows two stars, X and Y.
From information given in the diagram, which statement below is correct?		 HR diagram showing 2 stars X and Y
  • A. X is further away from us than Y
  • B. Y is further away from us than X
  • C. X has a larger surface area than Y
  • D. Y has a larger surface area than X