Astronomy Ch 12

1. Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?

Mass they form with

2. A star’s luminosity is the

Total amount of energy that the star radiates each second

3. If distance between us and a star is doubled, w/ everything else remaining the same, its luminosity

remains the same, but its apparent brightness is decreased by a factor of 4

4. Which of the following statements about apparent and absolute magnitudes is true?

All statements are true (A star absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from earth, A star w/ an apparent magnitude of 1 appears brighter than a star w/ an apparent magnitude of 2, The absolute magnitude of a star is another measure of its luminosity, & The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared)

5. The spectral sequence sorts stars according to

Surface temperature

6. The stellar spectral sequence, in order of decreasing temperature, is

OBAFGKM

7. Which of the following stars are brightest at ultraviolet wavelengths?

O and B stars

8. You see two main-sequence stars w/ the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude, assuming there is no absorption of either star’s light by interstellar gas or dust?

Star 1 is 10 times more distant than Star 2.

9. Which of the following terms is given to a pair of stars that appear to change position in the sky, indicating that they are orbiting one another?

Visual Binary

10. Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?

surface temperature on the horizontal axis and luminosity on the vertical axis

11. On a Hertzsprung-Russell diagram, where would you find stars that are cool and dim?

lower right

12. On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous?

upper right

13. On a Hertzsprung-Russell diagram, where would you find stars that have the largest radii?

upper right

14. On a Hertzsprung-Russell diagram, where would you find red giant stars?

upper right

15. On a Hertzsprung-Russell diagram, where would you find white dwarfs?

lower left

16. On the main sequence, stars obtain their energy

by converting hydrogen to helium

17. Which of the following is the most numerous type of main-sequence star?

An M star

18. A star of spectral type G lives approximately how long on the main sequence?

10 billion years

19. Which of the following comparisons between low-mass stars and high-mass main-sequence stars is true?

Low-mass stars are cooler and less luminous than high-mass stars

20. Which of the following statements about open clusters is true?

All stars in the cluster are approximately the same age.

21. The age of stars in a cluster can be determined by

determining the main sequence turnoff point.

22. You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster?

10 billion years

23. Use the H-R Diagrams in your textbook to answer the following:

What is the approximate surface temperature of an F star?

7,000 K, 12,000 K, or 5,000 K Not 6,000 K I got this answer wrong

24. Use the H-R Diagrams in your textbook to answer the following:

What is the approximate surface temperature of a B star?

20,000 K

25. Use the H-R Diagrams in your textbook to answer the following:

What is the spectral type of a main sequence star with a luminosity 100 times greater than the sun?

A

26. Use the H-R Diagrams in your textbook to answer the following:

What is the approximate luminosity of a main-sequence M star?

0.01 times the sun’s luminosity

27. Use the H-R Diagrams in your textbook to answer the following:

A star is observed with a surface temperature of 3,000 K and a luminosity of 10−2 times the sun’s luminosity. What is the approximate radius of this star?

1 solar mass, The radius cannot be determined or 0.3 solar radius Not 0.1 solar radius Got this wrong

28. How does the rate of hydrogen consumption of a main-sequence B star compare to the hydrogen consumption of our sun?

The "B" star consumes hydrogen at a rate faster than the sun.

29. If the distance between us and a star is doubled, its apparent brightness will decrease by a factor of four.

True

30. The more distant a star, the smaller its parallax.

True

31. We can measure the parallax of most stars in our galaxy.

False

32. Which main-sequence star has the lowest mass?

M