PHYS 107 ASTRONOMY 10

• Question 1

  1 out of 1 points

  	Suppose that the calibration of the Cephiod period-luminosity relationship was uncertain and resulted in distances uncertain by 30% in the Milky Way.  What would we see in the uncertainties in distances to Cephieds in other galaxies:
  	Selected Answer:   the uncertainty in distance would be at least 30% Correct Answer:  the uncertainty in distance would be at least 30% Response Feedback: Correct, any uncertainty in the calibration of nearby objects results in at least that uncertainty in more distant objects.

• Question 2

  1 out of 1 points

  	If all the "dark matter" in our universe were to be instantaneously removed, which of the following would not happen?
  	Selected Answer:    The Solar System would fly apart Correct Answer:   The Solar System would fly apart Response Feedback:  Correct, the Solar System is bound together by the mass of the Sun, and dark matter is not an appreciable part of this mass.

• Question 3

  1 out of 1 points

  	Why isn't the space within our solar system or the Milky Way expanding according to Hubble's Law?
  	Selected Answer:    The gravity exerted by the solar system and the Milky Way is strong enough to hold them together against the expansion of the universe. Correct Answer:    The gravity exerted by the solar system and the Milky Way is strong enough to hold them together against the expansion of the universe. Response Feedback:  Correct, objects bound together by gravity do no participate in the expansion of the Universe

• Question 4

  1 out of 1 points

  	Suppose the Hubble constant turned out to be 142 km/sec/mpc and not 71 km/sec/mpc. How would that affect our estimate of the age of the Universe?
  	Selected Answer:   The Universe would be about 7 billion yrs old. Correct Answer:  The Universe would be about 7 billion yrs old.

• Question 5

  1 out of 1 points

  	What holds galaxy clusters together?
  	Selected Answer:   The force of gravity. Correct Answer:  The force of gravity.

• Question 6

  1 out of 1 points

  	Why is the cosmic microwave background temperature so cool now?
  	Selected Answer:   The expansion of the Universe has cooled the radiation and stretched its wavelengths. Correct Answer:  The expansion of the Universe has cooled the radiation and stretched its wavelengths.

• Question 7

  1 out of 1 points

  	Observations of the tiny irregularities in the cosmic microwave background support the idea that the Universe:
  	Selected Answer:   will expand forever. Correct Answer:  will expand forever.

• Question 8

  1 out of 1 points

  	What do astronomers infer from the motion of the distant galaxies?
  	Selected Answer:   The Universe is expanding. Correct Answer:  The Universe is expanding.

• Question 9

  1 out of 1 points

  	Why do we call dark matter "dark"?
  	Selected Answer:    It emits little or no radiation of any wavelength. Correct Answer:    It emits little or no radiation of any wavelength. Response Feedback:  Correct, except gravitationally dark matter does interact strongly with light at any wavelength

• Question 10

  1 out of 1 points

  	The following pattern shows a:
  	Selected Answer:   isotropic but not homogeneous pattern Correct Answer:  isotropic but not homogeneous pattern Response Feedback: Correct, it is isotropic (looking the same in all directions) but not homogeneous (as it does not have uniform density).

• Question 11

  1 out of 1 points

  	The following diagram shows a:
  	Selected Answer:   homogeneous but not isotropic pattern Correct Answer:  homogeneous but not isotropic pattern Response Feedback: Correct, it is homogeneous (having uniform density) but not isotropic as it looks different if you look up or down versus left and right.

• Question 12

  1 out of 1 points

  	Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?
  	Selected Answer:   measuring the amount of distortion caused by a gravitational lens  Correct Answer:  measuring the amount of distortion caused by a gravitational lens  Response Feedback:  Correct, gravitational lenses depend on Einstein's theory of general relativity

• Question 13

  1 out of 1 points

  	Suppose that we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?
  	Selected Answer:    the one that is farthest away Correct Answer:    the one that is farthest away Response Feedback:  Correct, the one furthest away from you is the one that is the furthest into the past and so closest to the Big Bang

• Question 14

  1 out of 1 points

  	I observe a galaxy that is 100 million light years away. Which of the following do I see?
  	Selected Answer:    the light from the galaxy as it was 100 million years ago, and it is redshifted Correct Answer:    the light from the galaxy as it was 100 million years ago, and it is redshifted Response Feedback: Correct, you see the galaxy as it was 100 million years ago since that is how long it takes for the light to reach us and it will be redshifted as the Universe is expanding do the galaxy will be moving away from us

• Question 15

  1 out of 1 points

  	Type Ia supernovae make good "standard candles" because they are all formed by:
  	Selected Answer:   white dwarfs that exceed 1.4 Solar masses Correct Answer:  white dwarfs that exceed 1.4 Solar masses