(T/F) The Galactic disk contains only old stars. |
F |
(T/F) Stars and gas in the Galactic disk move in roughly circular orbits around the Galactic center. |
T |
(T/F) Globular clusters trace out the structure of the Galactic disk. |
F |
(T/F) Herschel’s attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy’s size because he was unaware of absorption by interstellar dust. |
T |
(T/F) The most likely explanation of the high-speed motion of stars and gas near the Galactic center is that they are orbiting a supermassive black hole. |
T |
(T/F) Cepheid variables can be used to determine the distances to the nearest galaxies. |
T |
(T/F) The Galactic halo contains as much gas and dust as the disk. |
F |
(T/F) We can use 21-cm radiation to study molecular clouds. |
F |
Most of the mass of the Milky Way exists in the form of |
C. dark matter. |
The location of the galactic center was identified using |
c) red giant variable stars in globular clusters. Explanation: Harlow Shapley used pulsating RR-Lyrae variables as distance indicators to the globular clusters. He then deduced the distance and direction of the Milky Way’s center. |
When we observe stars near the center of the Milky Way Galaxy, we detect light that was emitted from those stars about: |
b) 25,000 years ago Explanation: (8000 pc)(3.3 ly/pc) ~ 25,000 ly |
Our Sun is located in the Milky Way Galaxy |
d) about halfway from the center, in the spiral arms. Explanation: The Sun orbits the center of the Galaxy within the disk, taking about 225 million years to complete one orbit. |
What two observations allow us to estimate the Galaxy’s mass? |
e) the orbital period and distance from the galactic center of objects near the edge of the Galaxy Explanation: Use the modified form of Kepler’s law to find the mass: Total mass = (orbital size)^3 / (orbital period)^2 |
A telescope searching for newly formed stars would make the most discoveries if it were pointed |
b) perpendicular to the Galactic disk |
The first stars that formed in the Milky Way now |
a) have chaotic orbits |
Stars in the outermost regions of the Milky Way Galaxy |
b) orbit faster than astronomers would expect based on the Galactic mass we can see |
(T/F) Most galaxies are spirals like the Milky Way. |
F |
(T/F) Most elliptical galaxies contain only old stars. |
T |
(T/F) Irregular galaxies, although small, often have lots of star formation taking place in them. |
T |
(T/F) Type I supernovae can be used to determine distances to galaxies. |
T |
(T/F) Most galaxies are receding from the Milky Way Galaxy. |
T |
(T/F) Hubble’s law can be used to determine distances to the farthest objects in the universe. |
T |
(T/F) Active galaxies can emit thousands of times more energy than our own Galaxy. |
T |
Using the method of standard candles, we could, in principle, estimate the distance to a campfire if we knew |
a) the number of logs used |
Within 30 Mpc of the Sun, there are about |
A. a few thousand galaxies. |
Hubble’s law states that |
B. the greater the distance to a galaxy, the greater is the galaxy’s redshift. |
If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be |
b) very small |
Quasar spectra |
a) are strongly redshifted |
Active galaxies are very luminous because they |
b) contain black holes in their cores |
(T/F) Intergalactic gas in galaxy clusters emits large amounts of energy in the form of radio waves. |
F |
(T/F) Distant galaxies appear to be much larger than those nearby. |
F |
(T/F) Collisions between galaxies are rare and have little or no effect on the stars and interstellar gas in the galaxies involved. |
F |
(T/F) The quasar stage of a galaxy ends because the central black hole swallows up all the matter around it. |
T |
(T/F) Elliptical galaxies may be formed by mergers between spirals. |
T |
(T/F) The fact that a typical quasar would consume an entire galaxy’s worth of mass in 10 billion years suggests that quasar lifetimes are relatively long. |
F |
(T/F) On the largest scales, galaxies in the universe appear to be arranged on huge sheets surrounding nearly empty voids. |
T |
(T/F) The image of a distant quasar can be split into several images by gravitational field of a foreground cluster. |
T |
A galaxy containing substantial amounts of dark matter will |
b) spin faster |
According to X-ray observations, the space between galaxies in a galaxy cluster is |
c) very hot |
The fraction of mass of the universe made up of dark matter is |
d) more than 90% |
In current theories of galaxy evolution, quasars occur |
a) early in the evolutionary sequence |
Many nearby galaxies |
d) may have been much more active in the past |
(T/F) Deep surveys of the universe indicate that the largest structures in space are about 50 Mpc in size. |
F |
(T/F) If the universe had an edge, the fact would violate the assumption of isotropy in the cosmological principle. |
F |
(T/F) Hubble’s law implies that the universe will expand forever. |
F |
(T/F) The cosmological redshift is a direct measure of cosmic expansion. |
T |
(T/F) The cosmic microwave background is the highly redshifted radiation of the early Big Bang. |
T |
(T/F) Observations suggest that the density of the universe is made up mostly of dark matter. |
F |
(T/F) The microwave background radiation last interacted with matter around the time of decoupling. |
T |
(T/F) The theory of inflation predicts that the density of the universe is exactly equal to the critical density. |
T |
Obler’s paradox is resolved by |
a) the finite size of the universe |
The galactic distances used to measure the acceleration of the universe are determined by observations of |
d) exploding white dwarfs |
On the basis of our current best estimate of the present mass density of the universe, astronomers think that |
c) the universe is infinite in extent and will expand forever |
The age of the universe is estimated to be |
d) greater than the age of the Milky Way Galaxy |
The horizon problem in the standard Big Bang model is solved by having the universe |
b) inflate rapidly early in its existence |
Astronomy 14-17
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