2. Compared to a white dwarf, neutron stars have

much smaller diameters but are less dense.
larger diameters and are less dense.
larger diameters and are much denser (more dense).
smaller diameters and are much denser.

3. Pulsars

are neutron stars that expand and contract in regular intervals.
can be any type of star that expands and contracts in regular intervals.
are neutron stars that spin fast.
can be any type of star that produces the "lighthouse effect".

4. Most supernova remnant clouds do not seem to have pulsars located within because

the beacon from the pulsar's "lighthouse" does not sweep over the Earth.
pulsars in time change into ordinary neutron stars.
pulsars in time collapse into black holes.
the gas in the remnant cloud contracts, becomes more dense and hides it.

5. A pulsar's energy is emitted

along the north and south axis (poles) of rotation.
along the north and south axis (poles) of its powerful magnetic field.
along the north and south axis (poles) of its strong gravitational field.
from the equatorial region only.

6. Choose the correct statement concerning the pulse rate for pulsars.

It is related to their spinning rate.
It ranges from a second to millionths of a second.
It is related to the rate at which the star's size oscillates.
It ranges from minutes to thousands of a second.

7. As pulsars age, their rate of spin tends to

speed up gradually due to the fact that the star shrinks in size.
slow down.
vary erratically due to loss of energy.
vary slightly up or down due to adjustments in the star's structure.

8. The range in masses for neutron stars is from (see Helps & Hints)

about 1 M_o to about 2.5 M_o.
greater than 1.4 M_o to about 2.5 M_o.
greater than 1.4 M_o to exactly 1.9 M_o.
about 1 M_o to exactly 1.9 M_o.

9. Most astronomers feel that the existence of large numbers of stellar black holes

is highly speculative.
is likely, but they probably cannot be found or identified.
is certain even though few have been found or identified to everyone's satisfaction.
has only a 50-50 chance of being true.

10. Cygnus X-1 is a black hole candidate according to some because it is

a binary star system; the invisible member of which has a mass greater than 3 M_o.
an X-ray source that spins like a neutron star.
a binary star system and the invisible member periodically eclipses the bright star.
dark and appears to be pulling matter into itself.

11. The perception astronomers have of black holes is

they are extremely dense, solid, black objects.
they are small (ten miles or so in diameter) spheres that will not allow light to escape because of their extreme gravitational pull.
they contain a singularity that is over one foot across.
have an event horizon that surrounds the ergosphere.

12. Which of the following is incorrect concerning the present theories about black holes according to the video?

The boundary (point of no return) is called the event horizon.
Near the event horizon, space itself is dragged along by a rotating black hole.
An infinitely dense singularity exist in the center.
Going into a black hole would probably also allow one to go back in time.

13. Black holes may give a lot more information about space and its curvature from a study of

their gravitational waves.
interferometry.
the neutrinos that leak out.
the fabric they emit into the space-time continuum.

14. Choose the incorrect statement concerning black holes. (see p. 222)

A person falling into a black hole would be greatly stretched.
Material falling towards a black hole is heated to millions of degrees.
Gamma rays are the only form of energy outside of neutrinos that can escape from a black hole.
X-rays may be emitted from an accretion disk that orbits a black hole.

15. The speed necessary to escape from a glack hole

depends on the mass (diameter) of the black hole.
equals the speed of light.
is greater than the speed of light.
is infinite.

Lesson 14 "The Milky Way"



16. In science, information is gathered and interpretations are made from the data. Select the set of statements that reflect an incorrect interpretation made by William Hershel or Harlow Shapley. (See p. 179, Study Guide.)

Hershel thought the Earth was in a flattened disk of stars. Shapley concluded we were not in the center of this star group or galaxy.
Hershel thought the Earth was in the center of a flattened disk of stars. Shapley concluded we were in a large globular cluster of stars.
Hershel thought the Earth was in a flattened disk of stars. Shapley demonstrated that the cluster of stars around us was much larger than Hershel thought.
Hershel systematically counted stars around us. Shapley concluded we were not in the center of this grouping of stars.

17. Harlow Shapley was able to determine the Earth's approximate position in our galaxy by

measuring the magnitudes of Cepheid variables in the Magellanic Clouds.
noting we were in the center of a globular cluster.
studying the distribution of globular clusters around our galaxy.
measuring the distances of Cepheid variables in the Magellanic Clouds.

18. Shapley determined distances across our galaxy by using the

Cepheid variable stars in globular clusters.
Cepheid variables in Population I groupings of stars.
Cepheid variables in open clusters.
distribution of heavy elements in stars around the galaxy.

19. Which of the following is a valid comparison of Population I and Population II stars?

Population I stars are older, bluer and in the disk or plane of our galaxy.
Population II stars are older, bluer and in the disk or plane of our galaxy.
Population I stars are younger, redder and in the disk or plane of our galaxy.
Population II stars are older, redder and in the halo around the bulge of our galaxy.

20. The stars found in the halo of our galaxy seem to be

richer in heavier elements.
mainly composed of just hydrogen and helium.
more variable in luminosity.
larger than those in the arms of the galaxy.

21. Stars, like our sun, that contain some heavy elements

are called second or third generation stars because these heavy elements were produced in previous stars (maybe in supernovae).
are referred to as complex stars because of their composition.
must be very old to give time for these elements to be produced by nuclear reactions.
must be young or the nuclear reactions would have consumed them.

22. Choose the correct statement concerning the motions of stars in and around our galaxy.

Stars in the disk (arms) move randomly; halo stars preserve their original motion.
Stars in the disk (arms) move randomly; halo stars move much faster.
Stars in the disk (arms) move around the center; halo stars preserve their original (fossil) motion.
Stars in the disk (arms) move much faster; halo stars move in concentric circles.

23. The Milky Way rotates about every (assume its age to be 15 billion years or so)

250 million years which means it has made about 60 rotations.
250,000 years which means it has made about 60,000 rotations.
250,000 years which means it has made over 500 rotations.
250 million years which means it has made about 20 rotations.

24. Dust obscures a lot of the Milky Way but we can still map the spiral arms by studying the

radio waves emitted from gas clouds of unknown composition.
radio waves emitted from the dust itself.
radio waves emitted from neutral hydrogen clouds.
21 centimeter lines emitted by the dust itself.

25. The shape of the spiral arms may be maintained by

stars that are thrown out from the center of our galaxy like water from a rotating sprinkler.
dust that is thrown out from the center of the galaxy like water from a rotating sprinkler.
density waves that compress gases and stimulate stellar formation.
density waves that push older halo stars together.

26. Compared to globular clusters, open clusters are

much smaller, have a dense stellar population and are located in the disk.
much larger, have a less dense stellar population and are located in the halo.
much larger, have a less dense stellar population and are located in the disk.
usually smaller, have a less dense stellar population and are located in the disk.

27. The very center of the Milky Way is best probed by studying the

visible light, microwave and x-rays from that region.
microwave, infrared, x-rays and gamma radiation from that region.
visible light, infrared and x-rays from that region.
visible light, infrared and gamma rays from that region.

28. Very near the center of our galaxy, stars seem to move faster and faster as one approaches that region. This is interpreted to mean that a strong

gravitational field from a 20-30 M_o black hole is present.
gravitational field from a 2-3 million M_o black hole is present.
magnetic field from a 2-3 million M_o black hole is present.
magnetic field from a 20-30 M_o black hole is present.

29. In our galaxy, bright new stars are still forming

in the spiral arms.
between spiral arms.
in the central bulge.
in the halo.

30. The term metal as used by astronomers refers to (see glossary)

mainly iron, nickel, magnesium or copper.
mainly iron, nickel, lead or copper.
mainly iron, nickel, lead or magnesium.
elements heavier than hydrogen or helium.

Prepared by: Mike Mitchell

Be sure to review your quizzes before taking the test.