Download Test#3

1. A measurement of the parallax of a star allows us directly to determine the star's
a) rotation rate, b) temperature, c) distance, d) age
2. How much brighter would a star be if an observer moved from 3 to 1 parsec from the star?
a) 3 times, b) 9 times, c) 27 times, d) 81 times
3. The difference between the apparent and absolute magnitudes of a star is a measure of the star's
a) luminosity, b) temperature , c) brightness as we perceive it, d) distance
4. How do the Sun, a white dwarf, and a red giant rank in descending order of luminosity?
a) Sun, white dwarf, red giant, b) red giant, white dwarf, Sun,
c) red giant, Sun, white dwarf, d) white dwarf, Sun, red giant
5. Which of the following can produce a continuous spectrum?
a) a cold gas at low density, b) a hot gas at low density
c) a gas consisting entirely of molecules, d) a hot solid
6. The property of a star which determines its spectral class is its
a) chemical composition, b) temperature, c) radial velocity, d) rate of rotation
7. The hottest stars have spectral class
a) O, b) A, c) G, d) M
8 An HR diagram for a group of stars can be produced by plotting their
a) masses versus ages, b) magnitudes versus spectral types
c) temperatures versus colors, d) distances versus luminosities
9. Why are there more main sequence stars than giant stars?
a) the main sequence stage for a star is longer than the giant stage
b) giants are dim and hard to see
c) most giant stars are drawn to the core of the galaxy
d) few stars first form as giants rather than main sequence stars
10. Hydrostatic equilibrium describes the balance between
a) mass and luminosity, b) pressure and gravity,
c) temperature and density, d) radius and luminosity
11. The Sun is
a) an average star in mass and radius
b) a much larger than average star, but with an average mass
c) a much smaller than average star, but with an average mass
d) an average size star, but with much larger than average mass
12. Approximately how long is the main sequence lifetime of the Sun?
a) 10 billion years, b) 1 billion years, c) 100 million years, d) 10 million years
13. Most of the energy produced in the Sun's core is carried away from the core by
a) neutrinos, b) convection, c) conduction, (d) radiation
14. In the outer 20 percent of the Sun's atmosphere energy is transported by
a) conduction, b) radiation, c) convection, d) winds
15. The two most abundant elements in the Sun are
a) hydrogen and helium, b) iron and silicon, c) nitrogen and oxygen, d) hydrogen and oxygen
16. The Maunder minimum is
a)
b)
c)
d)
a period of time during which there were few if any sunspots
the lowest temperature found on the Sun's surface
the lowest latitude at which sunspots are found
the minimum size that a sunspot may have
17. Why do sunspots appear dark?
a) they emit no light
b) they are transparent and let us see deeper, darker layers
c) they are cooler than their surroundings
d) they are shadows
18. New stars are formed from
a) the collision of one or more stars
b) the gas in the interstellar medium
c) coalescence of planets
d) cosmic rays trapped in a magnetic field
19. What happened to the gas which was left over in the solar nebula after the planets formed?
a) it was blown away by a strong wind
b) it fell back into the Sun
c) it was swept away by a passing star
d) it condensed to form the zodiacal light
20. The least massive stars in which nuclear fusion occurs have masses of about 8 percent that of the Sun.
Why don't less massive objects ever experience nuclear fusion?
a) they explode before fusion can begin
b) they collide with other objects and increase their masses
c) they never become hot enough for fusion to occur
d) they become black holes before fusion can begin
21. What do all main sequence stars have in common?
a) they are all yellow
b) they are all consuming hydrogen in their cores
c) they are located near the Sun in space
d) they are all among the most luminous stars
22. The most important factor affecting a star's main-sequence lifetime is
a) radius, b) mass, c) percentage of metals, d) hydrogen to helium ratio
23. The main sequence lifetime of an O star compared with an M star is
a) much longer because there is more fuel available
b) much shorter because the O star 'burns' fuel at a much faster rate
c) about the same because all stars live about 10 billion years
d) trick question - lifetime depends on other parameters
24. Which of the following cannot be assumed about the stars in a given cluster?
a) they all have nearly the same distance from us
b) they all had the same initial chemical composition
c) they all have the same age
d) they all have the same mass
25. The fusion of iron nuclei does not occur in stable stars. Why not?
a) no star ever gets hot enough for iron fusion
b) elements more massive than iron aren't stable
c) iron fusion uses up energy instead of producing energy
d) iron is destroyed in stars as soon as it is produced
26. What type of star is supported by the pressure produced by its degenerate electrons?
a) a white dwarf, b) a neutron star, c) a main sequence star, d) a pulsar
27. Which of the following is not true of neutron stars?
a) they rotate slowly, b) they are a few km in radius
c) they have large magnetic fields, d) some of them are observed to be pulsars
28. Which of the following objects can rotate a thousand times per second without being torn apart?
a) white dwarf, b) main sequence star, c) red giant, d) neutron star
29. The object at the center of the Crab Nebula is
a) a massive O star, b) a neutron star, c) a 10 solar mass black hole , d) an X-ray binary
30. Pulsars are
a) spinning neutron stars with beamed radio emission
b) black holes with accretion disks
c) pulsating red giant stars with close companions
d) white dwarfs with periodic stellar winds
31. A pulsar spins rapidly because
a) it conserved angular momentum when it shrank
b) it has been struck a glancing blow by another star
c) it has formed from a very rapidly rotating gas cloud
d) it has been accelerated by explosions on its surface
32. Electrons moving in a magnetic field produce radiation by the process of
a) synchrotron radiation, b) black body emission
c) bright line emission, d) electron scattering
33. What kind of telescope was used to detect the first known neutron star?
a) a radio telescope, b) an optical telescope
c) an orbiting ultraviolet telescope, d) an infrared telescope
34. According to general relativity, what effect does matter have on space?
a) matter causes space to exert gravitational forces
b) matter curves space
c) matter causes space to expand
d) matter causes space to contract
35. If the Sun were replaced by a black hole having a mass of one solar mass, what would happen to the
Earth's orbit?
a) the Earth would spiral inward, b) the Earth would jump to a smaller orbit
c) the size of the Earth's orbit would increase rapidly, d) the Earth's orbit would remain the same
36. A star which is discovered to be a binary system on the basis of the Doppler shifts of the spectral lines
of its two stars is called a
a) spectroscopic binary, b) astrometric binary, c) visual binary, d) eclipsing binary
37. Which type of binary star is revealed by periodic decreases in brightness?
a) spectroscopic binaries, b) eclipsing binaries, c) visual binaries, d) astrometric binaries
38. What information about a binary star system is sufficient to make it possible to find the sum of the
masses of the two stars?
a) orbital period and separation, b) distance and spectral type
c) age and temperature, d) chemical composition and absolute magnitude
39. The explosive burning of hydrogen on the surface of a white dwarf produces a
a) supernova, b) nova, c) pulsar, d) splitting of the white dwarf into a binary system
40. 21 cm radiation is produced by which element?
a) hydrogen, b) helium, c) carbon, d) iron