WSU ASTR 135 Exam 2
10-27-99
1. Granulation is caused bya. sunspots.
b. rising gas below the photosphere.
c. shock waves in the corona.
d. the solar wind flowing away from the corona.
e. the heating in the chromosphere.
2. Differential rotation of the sun
a. causes the heating in the chromosphere and corona that makes them hotter than the photosphere.
b. is caused by the magnetic dynamo inside the sun.
c. implies that the equatorial regions of the sun rotate more rapidly than the polar regions.
d. causes the sunspots to migrate slowly from the equator toward the poles as the sun rotates.
3. Most of the light we see coming from the sun originates in the
a. chromosphere.
b. photosphere.
c. corona.
d. sunspots.
e. magnetic field.
4. Sunspots are known to be magnetic phenomena because
a. Doppler shifts in spectral lines are observed.
b. the Zeeman effect is observed in sunspots.
c. collisional broadening is observed in spectral lines.
d. infrared observations indicate that the sunspots are cooler than their surroundings.
e. observations during eclipses reveal a very extensive photosphere.
5. Sunspots are dark because
a. regions of the photosphere are obscured by material in the chromosphere.
b. shock waves move through the photosphere.
c. the sun rotates differentially.
d. the strong magnetic field inhibits the currents of hot gas rising from below.
6. A recent sunspot maximum occurred in 1990, what is the year of the sunspot maximum that immediately follows the 1990 maximum if the solar cycle continues?
a. 1995 or 1996
b. 2001
c. 2006
d. 2012
7. Which of the following is TRUE about Sun's corona?
a. Is a halo tenuous million degree Kelvin gas.
b. It is cooler than the photosphere.
c. It can never be seen during daylight hours.
d. Sun must be the only star that has a corona.
8. Which of the following is evidence that convection occurs in the layers just below the sun's photosphere?
a. Sunspots appear to be cooler than their surroundings.
b. Solar prominences lift large loops of gas into the chromosphere and corona.
c. The solar wind emits large numbers of charged particles.
d. The sun rotates differentially.
e. The centers of granules are hotter than their edges.
9. The Sun is composed mostly of:
a. water
b. oxygen
c. nitrogen
d. hydrogen
10. The average density of the Sun is closest to:
a. iron
b. the Earth
c. white dwarf
d. water
11. The Babcock model explains the solar magnetic cycle as due to
a. bursts of solar wind particles produced by solar flares
b. helioseismology
c. the differential rotation and magnetic field of the Sun
d. coronal holes
12. Stellar parallax would be easier to measure if
a. Earth's orbit were larger.
b. the stars were farther away.
c. Earth moved faster along its orbit.
d. all of these
e. none of these
13. Absolute visual magnitude is
a. the apparent magnitude of a star observed from Earth.
b. the luminosity of a star observed from a distance of 1000 pc.
c. would be the apparent magnitude of a star observed from a distance of 10 pc.
d. the extinction of a star observed from Earth.
14. In the H-R diagram, 90 percent of all stars are
a. in the giant region.
b. in the supergiant region.
c. among the B stars.
d. among the Z stars.
e. on the main sequence.
15. The _____________ of a star is a measure of the total energy radiated by the star in one second.
a. absolute visual magnitude
b. apparent visual magnitude
c. spectral type
d. luminosity
16. To determine the period of a visual binary, we must measure
a. brightness.
b. position.
c. wavelengths.
d. luminosity.
e. temperature.
Use the following HR diagram to answer the next three questions.
17. Which star in the diagram above is most like the sun?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
18. Which star in the diagram above has the greatest surface temperature?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
19. Which of the stars in the diagram above has the largest absolute visual magnitude?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
20. A spectroscopic binary shows periodic variations in its
a. radial velocity.
b. proper motion.
c. brightness.
d. mass.
e. spectral type.
21. Stars on the main sequence with the greatest mass
a. are spectral type M stars.
b. are spectral type O stars.
c. are located at the bottom of the main sequence in the HR diagram.
d. have masses very similar to the sun.
22. The proton-proton chain needs high temperature because
a. of the ground state energy of the hydrogen atom.
b. of the presence of helium atoms.
c. the protons must overcome the Coulomb barrier.
d. of the need for low density.
e. the neutrinos carry more energy away than the reaction produces.
23. 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 spectral type K and M stars.
e. all of these.
24. Opacity is
a. the balance between the pressure and force of gravity inside a star.
b. the force that binds protons and neutrons together to form a nucleus.
c. the force that binds an electron to the nucleus in an atom.
d. a measure of the ease with which photons can pass through a gas.
e. the temperature and density at which a gas will undergo thermonuclear fusion.
25. If the sun produces energy by the proton-proton chain, then the center of the sun must have a temperature of at least
a. 104 K
b. 107 K
c. 1010 K
d. 1013 K
e. 1016 K
26. In the proton-proton chain
a. no neutrinos are produced.
b. energy is released because a helium nucleus has a smaller mass than the four hydrogen nuclei that produced it.
c. no photons are produced.
d. carbon serves as a catalyst for the nuclear reaction.
27. Due to the dust in the interstellar medium, a star will appear to an observer on Earth to be
a. brighter and cooler than it really is.
b. brighter and hotter than it really is.
c. fainter and cooler than it really is.
d. fainter and hotter than it really is.
e. unchanged in brightness or apparent color.
28. What defines a main-sequence star?
a. rapid rotation and strong stellar winds
b. fusion of hydrogen into helium in the core
c. the surface temperature
d. the apparent brightness
29. T Tauri stars are examples of
a. protostars
b. supergiants
c. white dwarfs
d. main-sequence stars
30. The nuclear process by which the Sun generates energy is most directly associated with
a. hydrogen's ability to combine with oxygen to cause "burning."
b. nuclear fission.
c. the energy holding atomic nuclei together.
d. radioactive decay.
31. The interstellar gas is composed mainly of:
a. hydrogen and helium
b. carbon
c. ammonia, methane, and water
d. iron
32. A star will experience a helium flash if
a. it is more massive than about 6 solar masses.
b. its core contains oxygen and helium.
c. its mass on the main sequence was less than 0.1 solar masses.
d. it is a supergiant.
e. its core is degenerate when helium ignites.
33. 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 neon
e. hydrogen, helium, carbon, neon, and oxygen.
34. A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion.
c. produced by a nova explosion.
d. a nebula within which planets are forming.
e. a cloud of hot gas surrounding a planet.
35. The Chandrasekhar limit tells us that
a. accretion disks can grow hot through friction.
b. neutron stars of more than 3 solar masses are not stable.
c. white dwarfs must contain no more than 1.4 solar masses.
d. the size of the event horizon.
36. Massive stars cannot generate energy through iron fusion 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 fusion requires more energy than it produces.
e. massive stars supernova before they create an iron core.
37. A nova is almost always associated with
a. a very massive star.
b. a very young star.
c. a star undergoing helium flash.
d. a white dwarf in a close binary system.
38. The Algol paradox is explained by considering
a. the degenerate nature of the hydrogen on the surface of the white dwarf.
b. synchrotron radiation
c. the rate of expansion of the shock wave inside the supernova.
d. the rotation rate of a neutron star.
e. mass transfer between the two stars in a binary system.
39. A type-II supernova
a. occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
b. is the result of helium flash.
c. occurs when the iron core of a massive star collapses.
d. is characterized by a spectrum that shows almost no hydrogen lines
40. All stars must eventually leave the main-sequence because
a. they deplete the hydrogen in their cores.
b. they use up the helium in their cores.
c. they use up the iron in their cores.
d. gravity weakens over time.
41. Why are star clusters good for stellar evolution studies?
a. The combined light of the stars makes them easier to see.
b. Star clusters are always located in the plane of the galaxy.
c. Stars in clusters began forming at the same time, have similar starting composition, and are at about the same distance away.
d. Stars in clusters are always very young and shine brightly.
42. The higher the mass of a main-sequence star
a. the faster hydrogen in the core is converted to helium.
b. the longer it will remain on the main-sequence.
c. the slower hydrogen in the core is converted to helium.
d. the lower the luminosity.
43. The density of a neutron star is
a. about the same as that of a white dwarf.
b. about the same as that of the sun.
c. about the same as an atomic nucleus.
d. about the same as a water molecule.
44. A neutron star is expected to spin rapidly because
a. they conserved angular momentum when they collapsed.
b. they have high orbital velocities.
c. they have high densities.
d. they have high temperatures.
45. In A. D. 1054, Chinese astronomers observed the appearance of a new star, whose location is now occupied by
a. a pulsar.
b. a neutron star.
c. a supernova remnant.
d. all of the above
e. none of the above
46. The event horizon
a. is believed to be a singularity.
b. is a crystalline layer.
c. has a radius equal to the Schwarzschild radius.
d. marks the inner boundary of a planetary nebula.
e. is located at the point where synchrotron radiation is created around a pulsar.
47. The search for black holes involves searching for
a. single isolated stars that emit large amounts of x-rays.
b. x-ray binaries where the compact companion has a mass in excess of 3 solar masses.
c. large spherical regions from which no light is detected.
d. pulsars with periods less than one millisecond.
48. A neutron star has a size of about
a. 10 cm
b. 20 km
c. 6000 km
d. 1 AU
49. Black holes are most easily identified
a. when their effect on a nearby star can be observed
b. by looking for locations in the sky where it is particularly dark
c. with the largest optical telescopes on Earth
d. when Earth is lined up along the magnetic axis of the black hole
50. The escape velocity at the event horizon of a black hole is
a. 100 m/sec
b. 1000 m/sec
c. the speed of light
d. twice the speed of light