Astronomy 1010 Exam #2 Chapter 7

The composition of the protoplanetary disk varies with distance from the protostar due to temperature. Starting with those closest to the protostar, place these materials in order based on where they can be found predominantly in their solid states.

closest Iron, silicates, carbon Water Methane, ammonia, CO farthest

In this video, angular momentum is only approximately conserved. This is because Choose one: A. there are small external forces acting—friction and air resistance, for example. B. no quantities are ever really conserved. C. the person on the platform is exerting a force when she pulls her arms in and pushes them out. D. the measurement of angular momentum depends on your reference frame.

A. there are small external forces acting—friction and air resistance, for example.

The following graph shows multiple transit events recorded while observing a star. The colored arrows indicate transits caused by three different planets. Rank the orbital periods of these planets, from shortest to longest.

Shortest period Red planet Blue planet Purple planet Longest period

Correctly position these four planets within the accretion disk of our early Solar System based on the materials that were present where they formed.

Temperature drops with distance of the protostar: Earth, Jupiter, Saturn, Uranus

The search for extrasolar planets has uncovered a phenomenon astronomers call a "hot Jupiter." If our Solar System had one, where would it orbit, relative to the other planets?

Closest to Sun Hot Jupiter Mercury Venus Earth Mars Jupiter Farthest from Sun

The diagram shown illustrates the location of the Solar System's eight planets and three large dwarf planets. Sort each object according to its basic composition.

Gaseous: Jupiter, Saturn, Uranus, Neptune Rocky: Mercury, Venus, Earth, Mars, Ceres Rocky/Ice mixture: Pluto, Eris

What causes this disk to form and flatten? Choose one: A. angular momentum B. linear momentum

A. angular momentum

A new star is forming inside this glowing cloud of gas. The dark band in the middle is made of a disk of thick dust, which obscures the light within it and hides the forming star from view. Newly forming stars are surrounded by gas and dust. Based on this observation--and your previous observations about the relative orbits, positions, and sizes of the planets--what is the most likely scenario for the formation of the Solar System? Choose one: A. A cloud of gas and dust collapsed into a flattened disk, within which the Sun and planets formed. B. Two stars collided and broke apart to form the Sun and the planets. C. A cloud of gas and dust collapsed into a spherical shape, within which the Sun and planets formed. D. The Sun formed by itself from a collapsing cloud of gas and dust, then later gravitationally captured the planets as they happened to pass by.

A. A cloud of gas and dust collapsed into a flattened disk, within which the Sun and planets formed.

What is an accretion disk, and what are its characteristics? Select the true statements regarding accretion disks. Choose one or more: A. Conservation of angular momentum leads a cloud to form a disk rather than collapse entirely. B. An accretion disk forms because there is nothing to stop the collapse of an interstellar cloud toward its axis of rotation. C. The shape and motion of the accretion disk are the reason that the subsequently formed planets all orbit in or near the equatorial plane of the star. D. Most of the material in an accretion disk that does not end up in the protostar is available to form its planets. E. An accretion disk's radius is typically hundreds of AU.

A. Conservation of angular momentum leads a cloud to form a disk rather than collapse entirely. C. The shape and motion of the accretion disk are the reason that the subsequently formed planets all orbit in or near the equatorial plane of the star. E. An accretion disk's radius is typically hundreds of AU.

Study this picture of a meteorite that has been sliced open to show its interior, and use your observations to determine the most likely formation scenario for a planet. Choose one: A. A single isolated clump inside the nebula gravitationally collapses into a planet. B. Individual particles in the nebula stick together to form larger pieces which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet. C. All of the gas in the nebula collapses to the center to form the Sun, which then expels a piece of itself in a violent solar flare that is blown outward and becomes a planet.

B. Individual particles in the nebula stick together to form larger pieces which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet.

Comparing objects in a related group can reveal patterns among them. These patterns in turn can help us learn more about those objects than we could by studying each individually. With this goal in mind, watch this animation of the planets in the Solar System and select all of the following choices that describe the patterns that you've observed. As you do so, think about the implications of how the Solar System may have formed. Choose one or more: A. The size of all planets increases with distance from the Sun. B. Planets orbit the Sun in random directions. C. All planets orbit the Sun in a roughly flat plane. D. The closest planets to the Sun are much smaller than the planets that are farther away. E. The orbits of the outer planets (those most distant from the Sun) are spaced farther apart from one another than the orbits of the inner planets. F. The orbits of the planets are evenly distributed in distance from the Sun. G. All planets orbit the Sun in the same direction. H. All planets orbit the Sun in a spherical distribution.

C. All planets orbit the Sun in a roughly flat plane. D. The closest planets to the Sun are much smaller than the planets that are farther away. E. The orbits of the outer planets (those most distant from the Sun) are spaced farther apart from one another than the orbits of the inner planets. G. All planets orbit the Sun in the same direction.

Study the sizes of the gas giants shown in the image above (the distance from the Sun increases from left to right), and choose the best explanation that accounts for their differences in size. Choose one: A. Gas giants increase in size with increased distance from the Sun because more types of materials could condense farther out. B. Gas giants increase in size with increased distance from the Sun because the Solar Nebula was denser farther out. C. Gas giants decrease in size with increased distance from the Sun because the Solar Nebula was less dense farther out. D. Gas giants decrease in size with increased distance from the Sun because fewer types of materials could condense farther out.

C. Gas giants decrease in size with increased distance from the Sun because the Solar Nebula was less dense farther out.

Astronomers have determined that the gas giants are made mostly of hydrogen and helium. Given what you have learned about planetesimal formation through accretion, and the types of materials that condensed at certain distances from the Sun, which of the following is the most likely way that the gas giants formed? Choose one: A. Because hydrogen and helium could not condense into a solid at the temperature of the Solar Nebula, the gas giants must have formed elsewhere and been captured by the Sun's gravity. B. Hydrogen and helium condensed into a solid and accreted to form the gas giants. C. Rock, metal, and ices made of materials such as water, ammonia, and methane, condensed into a solid and grew large enough to gravitationally attract hydrogen and helium gas from the Solar Nebula.

C. Rock, metal, and ices made of materials such as water, ammonia, and methane, condensed into a solid and grew large enough to gravitationally attract hydrogen and helium gas from the Solar Nebula.

Based on the figure in the Introduction, and the fact that an object with an increasing moment of inertia will spin more slowly to conserve angular momentum, choose the figure that best depicts how a cloud of gas will collapse to form a star system. Choose one: A. round clouds, big to little B. horizontal clouds, big to little C. diagonal clouds, big to little

C. diagonal clouds, big to little

What is the name of the brown disk rotating around the protostar in the following image? Choose one: A. stellar disk B. planetary disk C. protoplanetary disk D. protostellar disk

C. protoplanetary disk

Imagine that a star-forming cloud collapses but retains all of its mass in a single blob. In order to conserve angular momentum, the cloud must Choose one: A. spin slower. B. spin at the same rate. C. spin faster. D. come to a complete stop.

C. spin faster.

The terrestrial planets and the giant planets have different compositions because Choose one: A. the terrestrial planets have few moons. B. the giant planets are much larger. C. the terrestrial planets are closer to the Sun. D. the giant planets are mostly made of solids.

C. the terrestrial planets are closer to the Sun.

If a quantity is conserved, it means that it Choose one: A. can be saved for a later time. B. changes only if an external force acts. C. changes only if an internal force acts. D. it doesn't change.

D. it doesn't change.

Based on the law of conservation of angular momentum, what would happen to a collapsing cloud of gas and dust--isolated in space with no external forces--as its size decreases? Choose one: A. The cloud will gain mass. B. The cloud will spin more slowly. C. The cloud will lose mass. D. The cloud will not be able to collapse at all. E. The cloud will spin faster.

E. The cloud will spin faster.

Rank the following events in the order that corresponds to the formation of a planetary system.

Earliest Gravity collapses a cloud of interstellar gas. A rotating disk forms and dust grains stick together by static electricity. Small bodies collide to form larger bodies. Primary atmospheres form. A stellar wind "turns on" and sweeps away gas and dust, removing primary atmospheres from planets. Secondary atmospheres form. Latest

Put the following stages of planet formation in order of occurrence.

Earliest stage An interstellar cloud collapses into a disk of gas, dust. Gas pushes smaller dust grains into larger grains. Larger dust grains grow into clumps. Clumps of dust collide and stick, forming planetesimals. Km-sized planetesimals attract other objects by gravity. Planets of various sizes form. Latest stage

The diagram shown indicates the location of exoplanets orbiting their star. The light green ring represents the habitable zone for that star. Determine whether each of the planets in this system is located in a region that is too hot, too cold, or just right for liquid water to potentially exist on the surface.

Too hot for liquid water: Planets B, C, D, E Too cold for liquid water: Just right for liquid water: Planet F