The hydrogen lines in spectral type A stars

1. The hydrogen lines in spectral type A stars • are most narrow for supergiants. • are most narrow for main sequence stars. • can not be used to estimate the luminosity of the star. • are very weak and difficult to see. • are useful in determining the apparent magnitude of the star.

2. Parallax would be easier to measure if • Earth's orbit was larger. • the stars were farther away. • Earth moved faster along its orbit. • all of these. • none of these.

3. Absolute visual magnitude is • the apparent magnitude of a star observed from Earth. • the luminosity of a star observed from a distance of 1000 pc. • the apparent magnitude of a star observed from a distance of 10 pc. • the luminosity of a star observed from Earth. • 3 and 4.

4. A star's luminosity depends only on the star's • distance and diameter. • temperature and distance. • distance. • temperature and diameter. • apparent magnitude.

5. In an H-R Diagram, stars with the smallest radius are found in the ____ of the diagram. • center • upper left corner • upper right corner • lower left corner • lower right corner

6. In the H-R diagram, 90 percent of all stars are • in the giant region. • in the supergiant region. • among the B stars. • among the G stars. • on the main sequence.

7. We know that giant stars are larger in diameter than the sun because • they are more luminous but have about the same temperature. • they are less luminous but have about the same temperature. • they are hotter but have about the same luminosity. • they are cooler but have about the same luminosity. • they have a larger absolute magnitude than the sun.

8. Red giant stars areI. more luminous than the sun.II. larger in diameter than the sun.III. cooler than B stars.IV. located above the main sequence stars in the H-R diagram. • I & II • II & IV • I, II, & IV • II, III, & IV • I, II, III, & IV

9. Compared with the spectral lines in the solar spectrum, lines in a supergiant star’s spectrum are • narrower. • broader. • weaker. • stronger. • 2 & 3.

10. The most common stars are • supergiants. • giants. • upper (more luminous) main sequence stars. • white dwarfs. • lower (less luminous) main sequence stars.

11. The ____ of a star is a measure of the total energy radiated by the star in one second. • color • apparent visual magnitude • luminosity class • spectral type • luminosity

12. The star named Sheat is of spectral type M2 and luminosity class II. Based on this information,I. Sheat is cooler than the sun.II. Sheat has a greater diameter than the sun.III. Sheat is more luminous than the sun.IV. Sheat is located near the upper left hand corner in the HR diagram. • I & II • II & IV • II, III, & IV • I, II, & III • I, II, III, & IV

13. The star named Circini is of spectral type and luminosity class O8.5 V. Therefore,I. Circini has a surface temperature less than the sun.II. Circini has a diameter that is greater than that of the sun.III. Circini is more luminous than the sun.IV. Circini is located near the upper left hand corner in the HR diagram. • I & II • II & IV • II, III, & IV • I, II, & III • I, II, III, & IV 13

14. To determine the orbital period of a visual binary, we must measure • brightness. • positions on the sky. • wavelengths. • luminosity. • temperature.

15. In a binary system, the more massive star • is at the center of mass. • is farthest from the center of mass. • is nearest the center of mass. • follows the largest orbit. • shows a larger Doppler shift in its spectral lines.

16. The total mass of the pair of stars in spectroscopic binaries are difficult to estimate because • we can't measure the radial velocities of each star in the system. • we can't see the shape or tilt of the orbit. • we can't find the diameters of the stars. • we can't determine the luminosities of the stars. • the Doppler shift is not measurable.

17. Which star in the diagram below is most like the sun? • Alnilam • Antares • Arcturus • HR 5337 • Sirius B

18. Which star in the diagram below has the greatest surface temperature? • Alnilam • Antares • Arcturus • HR 5337 • Sirius B

19. Which of the stars in the diagram below has the largest absolute visual magnitude? • Alnilam • Antares • Arcturus • HR 5337 • Sirius B

20. An eclipsing binary will • be more luminous than a visual binary. • also be observed as a spectroscopic binary. • give off most of its light in the infrared. • show a constant Doppler shift in its spectral lines. • show two stars with variable proper motion.

21. If we can solve the orbital motion of an eclipsing binary, we can find • the mass of each star. • the diameter of each star. • the distance to the binary. • all of the above. • both A and B.

22. Which of the following kinds of stars best obey the mass-luminosity relation? • main sequence stars • giant stars • supergiant stars • white dwarfs • all of the above

23. Which of the following kinds of stars is most dense? • a supergiant star • a main sequence star • a giant star • a white dwarf • the sun

24. A spectroscopic binary shows periodic variations in its • radial velocity. • proper motion. • brightness. • mass. • spectral type.

25. Stars on the main sequence with the greatest mass • are spectral type M stars. • are spectral type O stars. • are located at the bottom of the main sequence in the HR diagram. • have masses very similar to the sun. • both 2 and 3.

26. The star Algol is • an astrometric binary. • a spectroscopic binary. • a visual binary. • an eclipsing binary. • both B and D.

27. The total mass of a binary system can be calculated from • the ratio of the angular separation from the center of mass of each of the stars. • the distance to the binary and its radial velocity. • the semi major axis and period of the orbit. • the radial velocities of the two stars. • the time required for the small star to eclipse the larger star.

28. The diagram below illustrates two stars in a visual binary system and the center of mass of this system. Based on this diagram, what is the ratio of the mass of star A to the mass of star B? • 2 to 1 • 1 to 2 • 2 to 3 • 3 to 2 • 1 to 3

29. If a star has a parallax of 0.02 seconds of arc, then its distance is • 20 pc • 50 pc • 2 pc • 5 pc • 500 pc

30. What is the total mass of a binary star system with P = 20 yr and a = 10 AU? • 2 solar masses • 2.5 solar masses • 0.5 solar mass • 80 solar masses • 0.4 solar mass

31. The diagram shows the radial velocity curve of a double-line spectroscopic binary. Based on this radial velocity curve, which of the following statements is correct? • Star A is twice the mass of star B. • Star B is twice the mass of star A. • Star A is ten times the mass of star B. • Star B is ten times the mass of star A. • Star A and Star B have the same mass.

32. According to this light curve, what is the period of the eclipsing binary? • 5 days • 32.5 days • 7.5 days • 42.5 days • 50 days 32

33. At what point in the light curve below is the cooler star in front of the hotter star? • 1 • 2 • 3 • 4 • 5

34. Which star in the table below is the closest to Earth? • δ Cen • HR 4607 • HR 4758 • HD 39801 • 9 CMa

35. Which star in the table below has the greatest surface temperature? • δ Cen • HR 4607 • HR 4758 • HD 39801 • 9 CMa

36. Which star in the table below has the greatest diameter? • δ Cen • HR 4607 • HR 4758 • HD 39801 • 9 CMa

37. If two stars are emitting the same amount of light, the star that is farther will appear • brighter. • dimmer. • redder. • bluer. • They will have the same brightness as seen from Earth.

38. Which stars always have large positive absolute magnitude? • Stars of high luminosity. • Stars of low luminosity. • Nearby stars. • Distant stars. • Not enough information given.

39. How do humans use their eyes to measure relative distance by parallax? • By continuously focusing our eyes on distant objects we can determine distance. • Since our eyes are separated the brain interprets the relative look angles of these eyes in terms of distance to the object viewed. • Our eyes can measure the time it takes light to travel from an object and from this we get distance. • By moving our heads from side to side our brain compares look angles from each of these positions to obtain the distance to the object viewed. 39

40. How can we tell that some stars are relatively close to us in the sky? • Some stars are occasionally eclipsed by the Moon, so they must be nearby. • Some stars vary in brightness caused by sunspots we can see because they are so close. • Some stars appear to be extremely bright and must therefore be very close to us. • Some stars appear to move periodically back and forth against the background stars because of the Earth's movement around the Sun.

41. The most accurate way to determine the surface temperature of a star is to study • the pattern of absorption lines from various atoms. • the relative intensities of light measured through different photometric filters. • the peak wavelength of the star's continuum blackbody spectrum. • pattern of emission lines that are on the star's spectrum.

42. If you compare two stars, • the one with the larger radius will always have the greater luminosity. • the one with the higher surface temperature will always have the greater luminosity. • the one with the smaller absolute magnitude will always have the greater luminosity. • the one with the larger surface area has the greater energy flux from its surface.

43. Stars in the upper right part of the Hertzsprung-Russell diagram are always ____ when compared to stars near the middle of the diagram. • cooler • brighter as seen from Earth • larger • smaller • more massive

44. How is a luminosity class assigned to a star? • By combining the apparent magnitude with the star's parallax. • By measuring the period of variability in the star's apparent magnitude. • By studying the absorption line width in the spectrum of the star. • By observing the angular size of the star's image in a photograph or digital image.

45. A star whose parallax is 0.01 seconds arc is at a distance of 1000 pc. • True • False

46. The absolute magnitude of a star is the apparent magnitude it would have if it were 10 pc from Earth. • True • False

47. The location of a star in the HR diagram indicates its temperature and intrinsic brightness. • True • False

48. Absorption lines in the spectra of supergiant stars are broader than the same spectral lines in main sequence stars of the same spectral type. • True • False

49. Giant stars are members of luminosity class III. • True • False

50. If a star is twice as hot as the sun and only half the sun's diameter, it will be less luminous than the sun. • True • False