Exam 4
Descriptive Astronomy
UCA

2001 November 27

Multiple Choice: Each question is worth 2 points for a total of 50 points possible.

1. The maximum possible mass for a neutron star is dictated by the maximum pressure

a. degenerate neutrons can provide.

b. degenerate electrons can provide.

c. gravity can provide.

d. from the triple-alpha reactions.

2. The short duration of a pulsar pulse indicates the source of the pulse must be

a. massive.

b. only a few kilometers in size.

c. very old.

d. very dim.

3. The Schwarzschild radius is associated with

a. the maximum size possible for a white dwarf star

b. the size of the cone of radiation emitted by pulsars

c. a nebula whose size allows it to eventually collapse to become a star

d. the size of the event horizon of a black hole

4. The search for black holes involves searching for

a. x-ray binaries where the compact companion has a mass in excess of 3 solar masses.

b. large spherical regions from which no light is detected.

c. single isolated stars that emit large amounts of x-rays.

d. pulsars with periods less than one millisecond.

5. A neutron star has a size of about

a. 10 cm

b. 20 km

c. 6000 km

d. 1 AU

6. The density of a neutron star is

a. about the same as that of the sun.

b. about the same as an atomic nucleus.

c. about the same as that of a white dwarf.

d. about the same as a water molecule.

7. Galactic halo stars

a. do not orbit the galactic center.

b. have stronger magnetic fields than disk stars.

c. have randomly oriented orbits around the galactic center.

d. are mostly massive O and B stars.

8. The mass of the Milky Way is found from its

a. rotation curve.

b. light curve.

c. density wave.

d. Chandrasekhar limit.

9. Spiral arms trace the location of

a. black holes

b. cool gas clouds and the youngest stars.

c. the oldest stars in the galaxy.

d. white dwarfs.

10. Disk stars

a. contain the least amount of heavier elements.

b. are found mostly in globular clusters.

c. have highly elliptical orbits.

d. orbit the galactic center in circular orbits in roughly the same plane.

11. The more metal-rich a star

a. the younger the star.

b. the older the star.

c. the more massive the star.

d. the more luminous the star.

12. The Sun is located

a. at the center of our galaxy.

b. approximately 4 light years from the galactic center.

c. approximately 8 kpc from the galactic center.

d. approximately 2 Mpc from the galactic center.

13. Hubble's Law relates

a. galactic redshift and distance.

b. galactic mass and redshift.

c. redshift and radial velocity.

d. galactic class and mass.

14. The Local Group is an example of a

a. galactic super cluster.

b. rich galactic cluster.

c. void.

d. small galactic cluster.

15. Observations of galaxies indicate

a. 10 to 100 times more visible matter than dark matter.

b. 10 to 100 times more dark matter than visible matter.

c. most galaxies do not contain dark matter.

d. galaxies traveling backward in time.

16. Normal galaxies that are actively making new stars:

a. only spirals.

b. only ellipticals

c. only spirals and irregulars.

d. only Seyfert galaxies.

17. Dark matter

a. is seen in x-ray images.

b. is only seen in infrared images.

c. is detected only by its gravitational influence.

d. can be measured by counting all luminous matter.

18. Galactic collisions

a. may transform spiral galaxies into ellipticals.

b. involves the collision of most of the stars in the galaxies that are colliding.

c. have never been seen.

d. does not result in any changes to either of the galaxies involved.

19. The rotation curve of a galaxy is a plot of

a. stellar mass as a function of distance from the galactic center.

b. galactic mass as a function of their distance from the center of the universe.

c. orbital velocity of the stars as a function of distance from the galactic center.

d. redshift as a function of distance.

20. Active galactic nuclei (AGN) flicker on times scales as short as a week, this indicates

a. the mass of AGNs are small.

b. the diameter of AGNs are big.

c. the diameter of AGNs are relatively small.

d. the mass of AGNs are very big.

21. The large redshifts of quasars indicate

a. that they are at very large distances.

b. that they are in nearby galaxies.

c. that they are in the Milky Way galaxy.

d. they are moving very slowly.

22. Seyfert galaxies and BL Lac objects

a. have small but very luminous cores.

b. are normal spiral galaxies.

c. are normal elliptical galaxies.

d. have large but very dim cores.

23. Radio lobes of radio galaxies are emitting

a. a blackbody spectrum of light.

b. synchrotron radiation.

c. neutrinos.

d. dark matter.

24. The large amounts of energy released by active galaxies are probably the result of

a. matter falling into a supermassive blackhole.

b. supernovae.

c. novae.

d. galactic nucleosynthesis.

25. Radio galaxy lobes are the result of

a. neutron stars interacting with dark matter.

b. relativistic jets from the galactic nucleus interacting with the intergalactic medium.

c. dark matter in a magnetic field.

d. relativistic Doppler shifts.

Problems and Short Answer Questions: Each question is worth 10 points for a total of 50 points possible.

1. (3pts) Define Schwarzschild radius? (2pts) What type of object has a radius smaller than its Schwarzschild radius? (5pts) If the Sun where to become smaller than its Schwarzschild radius how would its appearance change, how would the orbit of the Earth change?

2. Galaxy Classification: Classify the galaxies below according to the Hubble classification scheme.

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3. Galactic Structure: Label the major structural parts of the galaxy below.

4. Describe the universal model for active galactic nuclei (AGN). List observational evidence that supports the AGN model.