Physics 335 Astronomy

Solution of Test 4 held on 4/30/01

1. Parallax would be easier to measure if
A. Earth's orbit was larger*
B. the stars were farther away
C. Earth moved faster along its orbit
D. the stars widely separate
 
2. To determine the period of a visual binary, we must measure
A. brightness
B. position with respect to background stars*
C. wavelengths
D. luminosity
 
3. Absolute visual magnitude of a star is
A. the magnitude observed from the Earth
B. equal to the luminosity of a star
C. the apparent magnitude of a star placed at a distance of 10 pc*
D. the luminosity of a star observed from the
Earth
 
4. A star's luminosity depends on the star's
A. distance and diameter
B. temperature and distance
C. distance
D. temperature and diameter*
 
5. In HR diagram, the main sequence stars with the smallest radius are found in the
A. center
B. upper left corner
C. upper right corner
D. lower right corner*
 
6. In the H-R diagram, 90 percent of all stars are
A. in the giant region
B. in the supergiant region
C. in the lower left region
D. on the main sequence*
 
7. Suppose you observe a previously unstudied star and find its apparent brightness. In order to determine its actual brightness, you need to find its
A. distance*
B. color
C. temperature
D. brightness as seen from Earth
 
8. The most common stars are
A. supergiants
B. giants
C. upper main sequence stars
D. lower main sequence stars*
 
9. The total energy radiated by a star in one second is
A. absolute visual magnitude
B. apparent visual magnitude
C. luminosity*
D. spectral type
 
10. An eclipsing binary will
A. be more luminous than a visual binary
B. always be a spectroscopic binary*
C. give off most of its light in the infrared
D. show a Doppler shift in its spectral lines
 
11. In a binary system, the more massive star
A. is at the center of the mass
B. is farthest from the center of mass
C. is nearest to the center of mass*
D. follows the larger orbit
 
12. Spectroscopic binaries show
A. Doppler shift in the spectrum*
B. tilt of the orbit
C. the stars as individuals
D. light curves all the times
 
13. If we can find the orbital speed and period of an eclipsing binary, we can find
A. the masses of the stars*
B. the diameters of the stars
C. the distance to the binary
D. Doppler shift
 
14. Which of the following best obey the mass luminosity relation?
A. main sequence stars*
B. giant stars
C. supergiant stars
D. white dwarfs
 
15. Which of the following stars is most dense?
A. a supergiant star
B. a main sequence star
C. a giant star
D. a white dwarf*
 
16. Stars on the main sequence of highest mass are
A. spectral type M stars
B. spectral type O stars*
C. located at the bottom of the main
sequence in the HR diagram
D. similar to the sun
 
17. The heavy elements greater than iron you are made of were formed in
A. the big bang
B. a supernova explosion*
C. the interior of a protostar
D. the interiors of a low mass star like the sun
 
18. The absolute magnitude of a star is the apparent magnitude it would have if it were
10 pc from Earth
A. True*
B. False
 
19. The location of a star in the HR diagram indicates its temperature and luminosity
A. True*
B. False
 
20. Giant stars are members of luminosity class III.
A. True*
B. False
 
21. The method of spectroscopic parallax cannot be applied to stars beyond 100 pc.
A. True
B. False*
 
22. The most common kind of stars is low-luminosity stars.
A. True*
B. False
 
23. Supergiants are about as common as the sun.
A. True
B. False*
 
24. White dwarfs have such a low luminosity that even the nearest white dwarfs are not visible to the naked eye.
A. True*
B. False
 
25. To observe a visual binary, we must measure radial velocities.
A. True
B. False*
 
26. To observe a spectroscopic binary, we must be able to see both stars individually.
A. True
B. False*
 
27. The most massive main-sequence stars are the M stars.
A. True
B. False*
 
28. Protostars are difficult to observe because
A. the protostar stage live for a very short time
B. they are surrounded by cocoons of gas and dust*
C. they radiate mainly in the x-rays
D. they are all so far away that the light has not reached us yet
 
29. The nuclear reactions in a star's core is regulated by
A. amount of mass available
B. pressure temperature thermostat*
C. density of matter in the star
D. size of the star
 
30. The proton-proton chain is a
A. nuclear reaction at the surface of the star
B. process for producing high atomic nuclei
C. reaction to overcome the Coulomb barrier
D. nuclear reaction in the core of a star*
 
31. Interstellar gas clouds may collapse to form stars if they
A. have very high temperatures
B. encounter a shock wave*
C. rotate rapidly
D. are located near main sequence
 
32. T Tauri stars appear to be
A. protostars*
B. Herbig-Haro objects
C. the result of globular clusters
D. long lived
 
33. Which of the following stars is hottest?
A. a red giant
B. a white dwarf*
C. the sun
D. a star detectable only in the infrared
 
34. The Hydrostatic equilibrium is the
A. balance between weight and pressure*
B. proton-proton chain
C. conservation of mass
D. The neutrino process
 
35. The reason astronomers use the concept of the intrinsic brightness is to
A. make life difficult for introductory astronomy student
B. make it harder for students with less math background
C. allow stars to be compared with the effects of differing mass removed
D. allow stars to be compared with the effects of differing distance removed*
 
36. In a degenerate matter
A. pressure depends only on the temperature
B. temperature depends only on density
C. pressure does not depend on temperature*
D. pressure does not depend on density
 
37. Stars are born in
A. reflection nebulae
B. dense molecular clouds*
C. the intercloud medium
D. the local bubble of galaxies
 
38. Neutrino is a subatomic particle produced in nuclear fusion that can travel through the sun and escape to space without interacting with any particles in the sun.
A. True*
B. False
 
39. Opacity is the resistance of a gas to
the flow or radiation.
A. True*
B. False
 
40. Ninety percent of all stars fuse helium to form carbon and lie on the main sequence.
A. True
B. False*
 
41. Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?
A. hydrogen
B. hydrogen and helium*
C. hydrogen, helium and carbon
D. hydrogen, helium, carbon and oxygen
 
42. The lowest-mass stars cannot become giants because
A. they do not contain helium
B. they rotate too slowly
C. they cannot heat their centers hot enough*
D. they contain strong magnetic fields
 
43. A planetary nebula is
A. the expelled outer envelope of a medium mass star*
B. produced by a supernova explosion
C. a nebula within which planets are forming
D. a cloud of hot gas surrounding a planet
 
44. The Chandrasekhar limit tells us that stars
A. must leave the main sequence
B. of more than 3 solar masses are not stable
C. of 1.4 solar mass or more cannot become white*
D. will end up as white dwarfs no matter what
 
45. Highly massive stars cannot produce elements higher than iron because
A. iron fusion requires very high density
B. stars contain very little iron
C. no star can get hot enough for iron fusion
D. iron is the most tightly bound of all nuclei*
 
46. A visual binary star is the one
A. whose brightness drops periodically as its companion passes in its front
B. whose members can be seen separated stars through a telescope*
C. which looks like a single star but its spectrum is explained by more than one star
D. whose proper motion reveals that it has planet-sized companions
 
47. Giant and supergiant stars are rare because that stage of stellar evolution is short.
A. True*
B. False
 
48. Stars less massive than 0.4 solar mass never become giant stars.
A. True
B. False*
 
49. assuming that stars radiate like black bodies, you must know which of the following properties in order to find the radius of a star?
A. luminosity and surface temperature*
B. luminosity and distance.
C. luminosity and flux.
D. luminosity and mass.
 
50. the most fundamental property of a star is its
A. temperature
B. luminosity
C. mass *
D. diameter