Download Test#4

PH109 Exploring the Universe, Test #4, Spring 2012
Please indicate the best answer to the following question on the answer sheet provided.
1. What kind of galaxy do we live in?
a) Spiral, b) elliptical, c) spherical, d) irregular
2. The size of our galaxy is about
a) 3 light years, b) 100 thousand light years, c) one mega parsec, d) unknown at the present
3. Hubble’s law describes a relationship between a galaxy’s
a) size and brightness, b) number of stars and size, c) shape and age, d) redshift velocity and distance
4. The distribution of matter in a galaxy can be found by measuring
a) the number of stars, b) the rotation curve, c) number of pulsars, d) how thick a galaxy is
5. What type of galaxy is the Andromeda galaxy M31)?
a) spiral, b) globular, c) elliptical, d) irregular
6. The distribution of galaxies in the universe
a) follows the same distribution as stars, b) arraigned on the surfaces of giant bubbles or voids
c) fairly uniform, d) has remained the same as it was during the big bang
7. The location of our Sun in the galaxy is approximately
a) near the core, b) near the outer edge
c) about 2/3 of the way out to the edge, d) not currently determined
8. About how long does it take for the Sun to complete one trip around the galaxy?
a) 25 thousand years, b) 2.5 million years, c) 250 million years, d) 25 billion years
9. We cannot see the other side of the galaxy primarily because our view is blocked by
a) too many stars, b) glowing interstellar gas, c) interstellar dust, d) planetary nebulae
10. A rotation curve for a galaxy is a plot of
a) orbital speed versus distance from center, b) number of rotations versus time
c) orbital distance versus eccentricity, d) temperature versus luminosity
11. The radio emission from radio galaxies and quasars is due to
a) thermal emission, b) blackbody radiation, c) O and B stars, d) synchrotron radiation
12. How do we know that the quasars are at large distances?
a) they are extremely dim, b) they have large redshifts,
c) they have large parallaxes, d) they are greatly obscured by interstellar dust
13. What is hardest to explain about spiral arm structure
a) that they ever existed in the first place, b) why galaxies only have two of them
c) why they have sharp boundaries, d) how they maintain themselves
14. For what type of object is the period-luminosity relation used for determining distances?
a) Algol variables, b) Cepheids, c) Cataclysmic variables, d) 21 centimeter radiation.
15. Why is our galaxy in the shape of a disk
a) because it rotates
b) because it got sheared off during a galactic collision
c) the outer parts were torn away by the Magellanic clouds
d) the dark matter holds it in that formation
16. If a galaxy is determined to be 2 million light years away, what does that mean
a) it takes light 2 million years to cross the galaxy
b) stars did not turn on till about 2 million years ago
c) it takes light 2 million years to reach us from the galaxy
d) if we could put our galaxy 2 million light years away it would look as bright as that galaxy.
17. Hubble’s law states that:
a) putting telescopes in space will cost approximately ten times more than ground based telescopes
b) the recession of one galaxy must equal the precession of another
c) the faster a galaxy moves away from us the more massive it is
d) the faster a galaxy moves away from us the farther away it is
18. When Galaxies collide
a) their stars collide to form larger stars, b) both galaxies crumple into very dense systems
c) they simply perturb each other’s shape, d) no galaxies are left after the collision
19. An Einstein ring is a
a) group of galaxies which forms a ring in inter-galactic space
b) something Al gave to his mother
c) the theory that say the universe is a continuous ring of space time
d) distortion of an image due to gravitational effects
20. The Magellanic clouds are
a) regions of star formation in the Andromeda galaxy
b) close clusters of galaxies about 10 megaparsecs away
c) nearby irregular galaxies gravitationally bound to the Milky Way
d) an optical illusion caused by dust in the interplanetary medium
21. How was Hubble able to determine the distances of nearby galaxies?
a) by using radar
b) by measuring trigonometric parallaxes
c) by measuring the typical angular separations of stars in them
d) by observing Cepheid variables in them
22. The 21 cm radiation form Hydrogen is observed by:
a) optical telescopes, b) radio telescopes, c) X-ray telescopes, d) neutrino telescopes
23. Why is the energy source of active galaxies thought to be extremely compact?
a) Their energy is totally no stellar in origin.
b) Their spectra are like those produced by ordinary stars.
c) They vary on rapid time scales.
d) They can be seen clearly; we can see that the energy source is compact.
24. Which of the following is not a characteristic of the stars of the disk component of our galaxy?
a. circular orbits, b. randomly inclined orbits, c. higher metal abundance, d. young stars
25. As matter streams into a black hole it usually forms what kind of structure
a) accretion disk, b) spherical shell, c) a dark nebula, d) star formation region
26. What is the easiest way to find the distance to a galaxy
a) Pallardy’s Law, b) Newton’s Laws, c) Einstein’s Law, d) Hubble’s Law
27. The very rapid orbital speed detected near the center of our galaxy suggests that
a) our galaxy has a lot of stored angular momentum, b) massive stars are at the center
c) a black hole is at the center, d) we have been in a collision in the past
28. What causes Cepheid variables to vary in brightness?
a) they pulsate, b) eclipses,
c) changes in nuclear energy generation rate, d) obscuration by clouds of dust
29. Where are globular clusters located in the galaxy?
a) in the nucleus, b) in the disk, c) in the spiral arms, d) in the halo
30. What observation of the Galaxy suggests it is much larger than the halo and contains a large amount of matter
not in the form of stars?
a) The rotation curve, b) Motions of the globular clusters
c) The shape of the spiral arms, d) Infrared observations of the center of the Galaxy
31. Quasars were originally discovered as
a) strong radio sources identified with star-like images on photographs
b) variable sources of light
c) bright galaxies, and only later found to be radio sources
d) the only type of radio source within our galaxy
32. The region between stars is:
a) empty, the stars have accreted all the mater, b) filled mostly with gas and dust
c) composed of dark nebulae, d) filled with emission nebulae
33. Why are quasars called “quasi-stellar”?
a) Their spectra strongly resemble the spectra of stars.
b) They are ordinary stars located at vast distances from Earth.
c) They look like stars on photographs.
d) Like the stars visible in our night sky, quasars reside within the boundaries of the Milky Way.
34. Which type of galaxy contains the least amount of interstellar material?
a) Ellipticals, b) spirals, c) barred spirals, d) irregulars
35. Most of the mass of a galaxy is
a. contained in the massive O and B stars in the galaxy.
b. contained in the H I regions of the galaxy.
c. contained in the H II regions of the galaxy.
d. contained in the dark matter of the galaxy.
36. 21 cm radiation is produced by which element?
a. hydrogen, b. helium, c. carbon, d. iron
37. Why do the cores of spiral galaxies appear redder than the arms
a) because of reddening due to dust, b) because the cores are older
b) because the cores are further away, d) because of black holes in the center
38. Irregular galaxies have ill defined shape because
a) they rotate too slow to form a disk, b) active star formation disrupts disk
c) too many black holes distort space time, d) recent collisions caused loss of shape
39. In the future our Milky Way galaxy will collide with what other galaxy?
a) small Magellanic cloud, b) large Magellanic cloud, c) Andromeda, d) Cepheid
40. If our galaxy has a black hole in the center, why don’t we see jets being emitted?
a) we are too close, b) we do, c) black hole fuel is gone, d) it is positioned sideways.