PHYS 107 ASTRONOMY 5

• Question 1

  1 out of 1 points

  	About how old is the Solar System?
  	Selected Answer:   5 billion years Correct Answer:  5 billion years

• Question 2

  1 out of 1 points

  	Based on our current theory of Earth's formation, the water we drink comes from:
  	Selected Answer:    comets that impacted Earth. Correct Answer:    comets that impacted Earth. Response Feedback:  Correct, ice likely formed well outside the part of the pre-Solar nebula that became the Earth.

• Question 3

  1 out of 1 points

  	The nebular theory of the formation of the solar system successfully predicts all but one of the following. Which one does the theory not predict?
  	Selected Answer:    the equal number of terrestrial and jovian planets (with the exception of Pluto) Correct Answer:    the equal number of terrestrial and jovian planets (with the exception of Pluto)

• Question 4

  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 5

  1 out of 1 points

  	Mercury's average density is about 1.5 times larger than the Earth's Moon even though the two bodies have similar radii. What does this suggest about Mercury's composition?
  	Selected Answer:   Mercury's interior is much richer in iron than the Moon's Correct Answer:  Mercury's interior is much richer in iron than the Moon's

• Question 6

  1 out of 1 points

  	What component of interstellar clouds became the inner planets?
  	Selected Answer:   The dust grains. Correct Answer:  The dust grains.

• Question 7

  1 out of 1 points

  	Which of the following is a consequence of the discovery of hot Jupiters for the nebular theory of solar system formation?
  	Selected Answer:    It has been modified to allow for planets to migrate inwards or outwards due to gravitational interactions. Correct Answer:    It has been modified to allow for planets to migrate inwards or outwards due to gravitational interactions. Response Feedback:  Correct, the apparent migration of planets is an important area of research today

• Question 8

  1 out of 1 points

  	How did the Solar System's shape develop?
  	Selected Answer:   The centripetal force slowed collapse perpendicular to the spin axis Correct Answer:  The centripetal force slowed collapse perpendicular to the spin axis Response Feedback: Correct, the fact the initial cloud was spinning meant that some material formed a disk instead of free falling into the Sun.

• Question 9

  1 out of 1 points

  	Why did the solar nebula heat up as it collapsed?
  	Selected Answer:    As the cloud shrank, its gravitational potential energy was converted to thermal energy. Correct Answer:    As the cloud shrank, its gravitational potential energy was converted to thermal energy. Response Feedback:  Correct, the gravitational potential energy was converted to kinetic energy, the thermal motion in the gas and dust.

• Question 10

  1 out of 1 points

  	What was the material out of which the Solar System formed primarily made of?
  	Selected Answer:   Mostly hydrogen and helium with a small amount of dust grains Correct Answer:  Mostly hydrogen and helium with a small amount of dust grains Response Feedback: Correct, the Universe is still mostly hydrogen and helium (from the Big Bang)

• Question 11

  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 12

  1 out of 1 points

  	What is meant by accretion?
  	Selected Answer:   The collection of material together to form a planet or star. Correct Answer:  The collection of material together to form a planet or star. Response Feedback: Correct, accretion is the growth of a massive object by gravitationally (or for small dust grains electro-statically) attracting more matter

• Question 13

  0 out of 1 points

  	Images taken while blocking the light coming directly from a young star sometimes show features like this because:
  	Selected Answer:   a and c Correct Answer:  a and b Response Feedback: Incorrect, this is the disk of dust and gas forming around a young star due to the conservation of angular momentum in which planets may form.

• Question 14

  1 out of 1 points

  	After the collapse began were all parts of the Solar Nebula the same temperature, and if not which part was hottest?
  	Selected Answer:   Not all the same temperature, and the inner parts were the hottest. Correct Answer:  Not all the same temperature, and the inner parts were the hottest.

• Question 15

  1 out of 1 points

  	What is the asteroid belt?
  	Selected Answer:   The region roughly in the plane of the orbit of the planets in the Solar System where most of the asteroids are found. Correct Answer:  The region roughly in the plane of the orbit of the planets in the Solar System where most of the asteroids are found.

• Question 16

  1 out of 1 points

  	Why are many of the newly detected extrasolar planets called "hot Jupiters"?
  	Selected Answer:    Their masses are similar to Jupiter but they are very close to the central star and therefore hot. Correct Answer:    Their masses are similar to Jupiter but they are very close to the central star and therefore hot. Response Feedback:  Correct, these are planets like Jupiter but much closer to the central star and so heated to a much higher temperature.

• Question 17

  1 out of 1 points

  	What had to happen to planetesimals to turn them into planets?
  	Selected Answer:   They had to collect together into larger objects via collisions and gravity. Correct Answer:  They had to collect together into larger objects via collisions and gravity. Response Feedback: Correct, electrostatic forces help to make small dust grains stick together, which allows them to form larger objects which can eventually gravitationally attract other objects.

• Question 18

  1 out of 1 points

  	How did planetesimals form?
  	Selected Answer:   By the accumulation and sticking of dust and solid particles in the proto-solar nebula. Correct Answer:  By the accumulation and sticking of dust and solid particles in the proto-solar nebula.

• Question 19

  1 out of 1 points

  	We currently know of approximately how many exo-planets?
  	Selected Answer:   900  Correct Answer:  900  Response Feedback: Correct, and increasing steadily.

• Question 20

  1 out of 1 points

  	Which method has been used to find most of the currently known exo-planets?
  	Selected Answer:   measurements of a stellar radial velocity shift Correct Answer:  measurements of a stellar radial velocity shift Response Feedback: Correct, although this may change due to the Kepler satellite