PHYS 107 ASTRONOMY 6

• Question 1

  1 out of 1 points

  	Which of the following is the phase of matter in the Sun?
  	Selected Answer:    plasma Correct Answer:    plasma Response Feedback:  Correct, essentially all of the material in the Sun is ionized

• Question 2

  1 out of 1 points

  	The low average densities of Jupiter and Saturn compared with the Earth suggests:
  	Selected Answer:   they contain large quantities of light elements, such as hydrogen and helium Correct Answer:  they contain large quantities of light elements, such as hydrogen and helium

• Question 3

  1 out of 1 points

  	How do the planets near the Sun differ from those farther out?
  	Selected Answer:   The ones nearest the Sun are generally smallest. Correct Answer:  The ones nearest the Sun are generally smallest.

• Question 4

  1 out of 1 points

  	Halley's comet has a period of 76 years and is in a very eccentric orbit that approaches at one point within 0.6 AU of the Sun, this means that it:
  	Selected Answer:   gets just past the orbit of Neptune Correct Answer:  gets just past the orbit of Neptune

• Question 5

  1 out of 1 points

  	In what direction does a comet's tail point?
  	Selected Answer:   Away from the Sun Correct Answer:  Away from the Sun

• Question 6

  1 out of 1 points

  	Jupiter's composition is closest to that of:
  	Selected Answer:   the Sun Correct Answer:  the Sun Response Feedback: Correct, both the Sun and Jupiter are mostly H and HeCorrect, both the Sun and Jupiter are mostly H and He

• Question 7

  1 out of 1 points

  	What is the most important reason why an icy moon is more likely to be geologically active than a rocky moon of the same size?
  	Selected Answer:    Ice has a lower melting point than rock. Correct Answer:    Ice has a lower melting point than rock.

• Question 8

  1 out of 1 points

  	Sunspots are cooler than the surrounding gas in the photosphere because:
  	Selected Answer:    strong magnetic fields slow convection and prevent hot plasma from entering the region. Correct Answer:   strong magnetic fields slow convection and prevent hot plasma from entering the region. Response Feedback:  Correct, the strong magnetic fields in these regions prevent charged particles from readily entering.

• Question 9

  1 out of 1 points

  	Why do all the planets orbit the Sun in the same direction?
  	Selected Answer:   They formed from material all circulating in the same direction in the primordial Solar Nebula Correct Answer:  They formed from material all circulating in the same direction in the primordial Solar Nebula Response Feedback: Correct, the direction of rotation was set by the initial rotation of the primordial cloud.

• Question 10

  1 out of 1 points

  	Why is Saturn almost as big as Jupiter, despite its smaller mass?
  	Selected Answer:    Jupiter's greater mass compresses it more and increasing its density Correct Answer:    Jupiter's greater mass compresses it more and increasing its density Response Feedback:  Correct, the greater mass of Jupiter means that gravity pulls it into a (relatively) more compact sphere

• Question 11

  1 out of 1 points

  	Why are objects like Mercury and the moons of Earth, Jupiter and Saturn so heavily cratered?
  	Selected Answer:   Intense bombardment by asteroids and planetesimals subsequent to their birth Correct Answer:  Intense bombardment by asteroids and planetesimals subsequent to their birth Response Feedback: Correct, the impact of small bodies leads to cratering and without tectonic activity, melting of ice or weathering the craters remain

• Question 12

  1 out of 1 points

  	What evidence can we see today that support the idea that there were planetesimals in the early Solar system?
  	Selected Answer:   All of the above. Correct Answer:  All of the above.

• Question 13

  1 out of 1 points

  	The Jovian planets retained most of their atmospheres because:
  	Selected Answer:   they were very cold when formed Correct Answer:  they were very cold when formed

• Question 14

  1 out of 1 points

  	The terrestrial planet cores contain mostly metal because:
  	Selected Answer:    metals sank to the center during a time when the interiors were molten throughout. Correct Answer:    metals sank to the center during a time when the interiors were molten throughout. Response Feedback:  Correct, this is differentiation

• Question 15

  1 out of 1 points

  	Uranus is peculiar because its:
  	Selected Answer:   axis of rotation is so highly tilted Correct Answer:  axis of rotation is so highly tilted Response Feedback: Correct, Uranus is tilted 98 degrees to its orbit and thus moves around the Sun on its "side", but not the part of Uranus pointed at the Sun is not always the same.

• Question 16

  1 out of 1 points

  	What makes some astronomers think that Uranus was hit by a large body early in its history?
  	Selected Answer:   Its rotation axis has such a large tilt with respect to its orbit Correct Answer:  Its rotation axis has such a large tilt with respect to its orbit

• Question 17

  1 out of 1 points

  	Why does Earth have the strongest magnetic field among the terrestrial worlds?
  	Selected Answer:    It is the only one that has both a partially molten metallic core and reasonably rapid rotation. Correct Answer:    It is the only one that has both a partially molten metallic core and reasonably rapid rotation. Response Feedback:  Correct, Venus and the Earth are nearly the same size, Mars and the Earth rotate at nearly the same rate, and Mercury, Venus and the Earth all have large metallic cores but only the Earth has a large metallic core and a rapid rotation rate.

• Question 18

  1 out of 1 points

  	Why aren't small asteroids spherical in shape?
  	Selected Answer:    The strength of gravity on small asteroids is less than the strength of the rock. Correct Answer:    The strength of gravity on small asteroids is less than the strength of the rock. Response Feedback:  Correct, the force of gravity is less than the force of the chemical bonds

• Question 19

  1 out of 1 points

  	Pluto is now classified as a dwarf planet because:
  	Selected Answer:   it is in the Kuiper belt Correct Answer:  it is in the Kuiper belt

• Question 20

  0 out of 1 points

  	Imagine a star which has the same luminosity as the Sun but which has a surface temperature that is twice that of the Sun. You would then expect that a planet identical to Earth orbiting at 1 AU from this star would:
  	Selected Answer:   be ~4x hotter than the Earth Correct Answer:  be approximately the same temperature as the Earth

• Question 21

  1 out of 1 points

  	Based on its surface temperature of ~5,800 K, most photons that leave the Sun's surface lie in which region of the electromagnetic spectrum?
  	Selected Answer:    Visible Correct Answer:    Visible Response Feedback:  Correct, remember Wein's Law

• Question 22

  1 out of 1 points

  	What evidence leads astronomers to think that Mars may once have had a milder climate?
  	Selected Answer:   Old canyons look like they were carved by running water. Correct Answer:  Old canyons look like they were carved by running water.

• Question 23

  1 out of 1 points

  	Jupiter is approximately 5 times further from the Sun than the Earth, for a square meter area on it's surface it emits   _____________ compared to a square meter on Earth:
  	Selected Answer:   less infrared light Correct Answer:  less infrared light

• Question 24

  1 out of 1 points

  	If the Sun were to suddenly expand to be 10 times its current size of ~0.0047 AU but keep the same mass, the Earth would:
  	Selected Answer:   stay in the same orbit Correct Answer:  stay in the same orbit Response Feedback: Correct, the force on the Earth would be unchanged since the mass of the Sun is unchanged, so the orbit would not change. Note this would not be true if the Sun were to expand to be larger than the Earth's orbit of course. Also note that orbital distances are defined from both object's centers, so while the Earth in some sense is "closer" to the Sun's surface, its distance from the Sun's center and hence its orbital distance is unchanged.

• Question 25

  1 out of 1 points

  	What is the solution to the solar neutrino problem?
  	Selected Answer:    The electron neutrinos created in the Sun's core change into another type of neutrino that we did not detect. Correct Answer:    The electron neutrinos created in the Sun's core change into another type of neutrino that we did not detect. Response Feedback:  Correct, neutrino oscillations change the types of neutrinos