Deck 6: Formation of Planetary Systems: Our Solar System and Beyond

Question 1

Which planet could an astronaut visit without the need for a spacesuit (and survive)?

A) Mercury
B) Venus
C) the Moon
D) Mars
E) None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar system.

Answer 1

E

Question 2

The planet closest in size to Earth is

A) Mercury.
B) Venus.
C) the Moon.
D) Mars.
E) Pluto.

Answer 2

B

Question 3

Why did the solar nebula flatten into a disk?

A) The interstellar cloud from which the solar nebula formed was originally somewhat flat.
B) The force of gravity pulled the material downward into a flat disk.
C) As the nebula cooled, the gas and dust settled onto a disk.
D) It flattened as a natural consequence of collisions between particles in the nebula, changing random motions into more orderly ones.

Answer 3

D

Question 4

Where did the elements heavier than hydrogen and helium come from?

A) They were produced in the Big Bang.
B) They evolved from hydrogen and helium shortly after the Big Bang.
C) They were produced inside stars.
D) They were produced inside dense interstellar gas.
E) All of the above

Question 5

Which of the following is not an exception to the general patterns of motion in the solar system?

A) the counterclockwise rotation of Venus
B) the large size of Earth's moon
C) the rings of Saturn
D) the extreme axis tilt of Uranus
E) the "backward" orbit of Triton around Neptune

Question 6

Where does nuclear fusion occur in the Sun?

A) on the surface
B) anywhere below the surface
C) in its core
D) just above the visible surface
E) all of the above

Question 7

Pluto is different from the other outer planets in all of the following ways except which one?

A) Its surface temperature is very cold.
B) It is made mostly of ices.
C) Its orbit is not very close to being circular.
D) It has only one moon.
E) It doesn't have rings.

Question 8

Which planet has a ring system?

A) Jupiter
B) Saturn
C) Uranus
D) Neptune
E) All of the above

Question 9

Which planet has the highest average surface temperature, and why?

A) Mercury, because it is closest to the Sun
B) Mercury, because of its dense carbon dioxide atmosphere
C) Venus, because of its dense carbon dioxide atmosphere
D) Mars, because of its red color
E) Jupiter, because it is so big

Question 10

Which of the following is not a characteristic of the inner planets?

A) They are relatively smaller than the outer planets.
B) They all have solid, rocky surfaces.
C) Their orbits are relatively closely spaced.
D) They all have substantial atmospheres.
E) They have very few, if any, satellites.

Question 11

Which is the densest planet in the solar system?

A) Mercury
B) Venus
C) Earth
D) Mars
E) Jupiter

Question 12

Where are most of the known asteroids found?

A) between the orbits of Mars and Jupiter
B) in the Kuiper belt
C) in the Oort cloud
D) between the orbits of the jovian planets
E) between the orbits of the terrestrial planets

Question 13

Astronomers now classify Pluto as really just a large member of

A) the asteroid belt.
B) the Kuiper belt.
C) the Oort cloud.
D) the moon system around Neptune.
E) an extrasolar planetary system.

Question 14

Which planet, other than Earth, has visible water ice on it?

A) Mercury
B) Venus
C) the Moon
D) Mars
E) Jupiter

Question 15

Which of the following observations indicates that conditions on Mars may have been suitable for life in the past?

A) There are very large extinct volcanoes on Mars.
B) There is a very deep and long canyon that extends across Mars.
C) There are dried-up riverbeds on Mars.
D) Mars has polar caps made of "dry ice."
E) Mars has two small moons.

Question 16

What are the main constituents of the jovian planets?

A) rocky minerals and water, as on Earth
B) hydrogen and helium
C) ammonia and methane
D) ammonia and water
E) nitrogen and methane

Question 17

Why did the solar nebula heat up as it collapsed?

A) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula.
B) As the cloud shrank, its gravitational potential energy was converted to thermal energy.
C) Radiation from other nearby stars that had formed earlier heated the nebula.
D) The shock wave from a nearby supernova heated the gas.
E) Collisions among planetesimals generated friction and heat.

Question 18

How does the Sun's mass compare with that of the planets?

A) It is a hundred times more massive than Earth.
B) It is a thousand times more massive than Earth.
C) It is a hundred times more massive than all the planets combined.
D) It is a thousand times more massive than all the planets combined.
E) It is about as massive as all the planets combined.

Question 19

Which of the following is furthest from the Sun?

A) Pluto
B) Neptune
C) an asteroid in the asteroid belt
D) a comet in the Kuiper belt
E) a comet in the Oort cloud

Question 20

Which of the following is not a characteristic of the outer planets?

A) They have very few, if any, satellites.
B) They all have large quantities of gas.
C) They are primarily made of hydrogen and helium.
D) Their orbits are separated by relatively large distances.
E) They all have rings.

Question 21

Which of the following has not been detected around other stars in the Galaxy?

A) a collapsing nebula of gas
B) flattened, spinning disks
C) jovian planets
D) terrestrial planets
E) strong stellar winds

Question 22

Which of the following puzzles in the solar system cannot be explained by a giant impact event?

A) the formation of the Moon
B) the large metallic core of Mercury
C) the backward rotation of Venus
D) the extreme axis tilt of Uranus
E) the orbit of Triton in the opposite direction to Neptune's rotation

Question 23

Based on our current theory of Earth's formation, the water we drink comes from

A) ice that condensed in the solar nebula in the region where Earth formed.
B) chemical reactions that occurred in Earth's crust after Earth formed.
C) chemical reactions that occurred in Earth's core after Earth formed.
D) material left behind during the giant impact that formed the Moon.
E) comets that impacted Earth.

Question 24

Observations of young stars (as well as theory) tell us that when the Sun was young, the solar wind

A) was weaker than it is today.
B) was stronger than it is today.
C) was about the same strength as it is today.
D) was nonexistent.
E) blew outward only along the Sun's poles.

Question 25

Which of the following is the origin of almost all the large moons around the jovian planets?

A) They are captured asteroids.
B) They are captured comets.
C) They are captured planets.
D) They were formed by condensation and accretion in a disk of gas around the planet.
E) They were formed by giant impacts.

Question 26

What percentage of the solar nebula's mass consisted of hydrogen and helium gases?

A) 0.5 percent
B) 5 percent
C) 50 percent
D) 98 percent
E) 100 percent

Question 27

Suppose you find a rock that contains some potassium-40 (half-life of 1.3 billion years). You measure the amount and determine that there are 5 grams of potassium-40 in the rock. By measuring the amount of its decay product (argon-40) present in the rock, you realize that there must have been 40 grams of potassium-40 when the rock solidified. How old is the rock?

A) 1.3 billion years
B) 2.6 billion years
C) 3.9 billion years
D) 5.2 billion years
E) none of the above

Question 28

The age of the solar system can be established by radioactive dating of

A) the oldest rocks on Earth.
B) the oldest rocks on the Moon.
C) the oldest meteorites.
D) the atmosphere of Mars.
E) It hasn't been done yet, but the age of the solar system could be obtained from a sample of Io's surface.

Question 29

Which of the following are relatively unchanged fragments from the early period of planet building in the solar system?

A) asteroids
B) Kuiper belt comets
C) Oort cloud comets
D) all of the above

Question 30

What do meteorites reveal about the solar system?

A) They reveal that meteorites are much older than the comets and planets.
B) Nothing, because they come from other star systems.
C) They reveal that the solar system once contained 10 planets.
D) They reveal that the age of the solar system is approximately 4.6 billion years.
E) They reveal that the early solar system consisted mostly of hydrogen and helium gas.

Question 31

According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?

A) The original solar nebula happened to be disk-shaped by chance.
B) Any planets that once orbited in the opposite direction or a different plane were ejected from the solar system.
C) The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.
D) The Sun formed first, and as it grew in size it spread into a disk, rather like the way a ball of dough can be flattened into a pizza by spinning it.
E) Luck explains it, as we would expect that most other solar systems would not have all their planets orbiting in such a pattern.

Question 32

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?

A) Planets orbit around the Sun in nearly circular orbits in a flattened disk.
B) the compositional differences between the terrestrial and jovian planets
C) the equal number of terrestrial and jovian planets (with the exception of Pluto)
D) the presence of asteroids and comets
E) the craters on the Moon

Question 33

What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium?

A) 0 percent
B) 0.1 percent
C) 2 percent
D) 20 percent
E) 80 percent

Question 34

Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?

A) Light gases (H, He), hydrogen compounds (H₂O, CH₄, NH₃), rocks, metals
B) Hydrogen compounds (H₂O, CH₄, NH₃), light gases (H, He), rocks, metals
C) Light gases (H, He), hydrogen compounds (H₂O, CH₄, NH₃), metals, rocks
D) Hydrogen compounds (H₂O, CH₄, NH₃), light gases (H, He), metals, rocks
E) Hydrogen compounds (H₂O, CH₄, NH₃), rocks, metals, light gases (H, He)

Question 35

According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?

A) Our theory is not quite correct because it cannot explain these exceptions.
B) Most of the exceptions are the result of giant impacts or close gravitational encounters.
C) The exceptions probably represent objects that formed recently, rather than early in the history of the solar system.
D) The exceptions probably represent objects that were captured by our solar system from interstellar space.
E) The exceptions exist because, even though our theory is as correct as possible, nature never follows rules precisely.

Question 36

Approximately how many other planetary systems have been discovered to date?

A) ten
B) a few hundred
C) a few thousand
D) tens of thousands
E) millions

Question 37

The heavy bombardment phase of the solar system lasted

A) several million years.
B) several tens of millions of years.
C) several hundreds of millions of years.
D) about a billion years.
E) to the present time.

Question 38

The first planets around other Sun-like stars were discovered

A) by Huygens, following his realization that other stars are Suns.
B) by Galileo following the invention of the telescope.
C) at the turn of last century.
D) about a decade ago.
E) at the turn of this century.

Question 39

What percentage of the solar nebula's mass consisted of rocky material?

A) 0 percent
B) 0.4 percent
C) 2 percent
D) 20 percent
E) 80 percent

Question 40

What kind of material in the solar nebula could remain solid at temperatures as high as 1,500 K, such as existed in the inner regions of the nebula?

A) rocks
B) metals
C) silicon-based minerals
D) hydrogen compounds
E) molecules such as methane and ammonia

Question 41

What are the two main differences between extrasolar planetary systems discovered to date and our Solar System?

A) Extrasolar planets tend to be more massive and dense than Jupiter.
B) Extrasolar planet orbits tend to be more eccentric and inclined than in our Solar System.
C) Extrasolar planet orbits tend to be closer and more eccentric than in our Solar System.
D) Extrasolar planet orbits tend to be closer and more circular than in our Solar System.
E) Extrasolar planets tend to be bigger and denser than Jupiter.

Question 42

Oceans cover more of Earth's surface than land.

Question 43

Which of the following is a consequence of the discovery of hot Jupiters for the nebular theory of solar system formation?

A) It has been discarded.
B) It has been modified to allow for the formation of gas giants within the frost line.
C) It has been modified to allow for planets to migrate inwards or outwards due to gravitational interactions.
D) Its status is unclear and awaits further observations that will determine whether hot Jupiters are dense Earth like planets or gas giants.

Question 44

The astrometric technique of planet detection works best for

A) large planets around nearby stars.
B) massive planets around nearby stars.
C) large planets around distant stars.
D) massive planets around distant stars.
E) planets in edge-on orbits.

Question 45

Most of the planets discovered around other stars

A) are more massive than Earth and orbit very far from the star.
B) are more massive than Earth and orbit very close to the star.
C) are less massive than Earth and orbit very far from the star.
D) are less massive than Earth and orbit very close to the star.
E) are found around neutron stars.

Question 46

Which of the following methods has led to the most discoveries of massive planets orbiting near their parent stars?

A) detecting the starlight reflected off the planet
B) detecting the infrared light emitted by the planet
C) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star's spectrum
D) detecting the shift of the star's position against the sky due to the planet's gravitational pull
E) detecting a planet ejected from a binary star system

Question 47

What is astrometry?

A) measuring distances to stars
B) searching for planets around stars
C) measuring the positions of stars on the sky
D) measuring the velocities of stars via the Doppler effect
E) using metric units for distance (e.g. meters rather than light years)

Question 48

Planets detected via the Doppler technique have been mostly

A) Earth-mass, in Earth-like orbits.
B) Jupiter-mass, in Jupiter-like orbits.
C) Jupiter-mass, in very close orbits.
D) Earth-mass, in very close orbits.
E) a wide range of masses, in edge-on orbits.

Question 49

The reason that most extrasolar planets are found close to their parent stars is

A) the planets reflect more light the closer they are to the star.
B) more of the starlight is blocked by the planet when it transits the star.
C) the Doppler shift of the star's spectrum is larger.
D) the closer to a star, the hotter and therefore brighter the planet is.
E) planets that are close to a star are heated up and therefore larger.

Question 50

Pluto is the largest solar system object beyond the orbit of Neptune

Question 51

Why are many of the newly detected extrasolar planets called "hot Jupiters"?

A) Their masses and composition are similar to what we would expect if Jupiter were hotter.
B) The planets tend to be detected around more massive, hotter stars than our Sun.
C) Their masses are similar to Jupiter but they are very close to the central star and therefore hot.
D) Their masses are similar to Jupiter but their composition is similar to Mercury.
E) because the discovery of other planets is very exciting

Question 52

Which planet search technique is currently best suited to finding Earth-like planets?

A) Doppler
B) astrometric
C) transit
D) gravitational lensing
E) combining all the above

Question 53

The jovian planets have no solid surface.

Question 54

How do we think the "hot Jupiters" around other stars were formed?

A) They formed as gas giants close to the star in the same orbits that they are seen today.
B) They formed as dense, rocky planets close to the star in the same orbits that they are seen today.
C) They formed as gas giants beyond the frost line and then migrated inwards.
D) Many planets were formed around the star but coalesced into a single planet close in.

Question 55

The transit method of planet detection works best for

A) big planets in edge-on orbits around around small stars.
B) big planets in face-on orbits around small stars.
C) small planets in edge-on orbits around big stars.
D) small planets in face-on orbits around big stars.
E) Earth-like planets in any orbit.

Question 56

The depth of the dip in a star's brightness due to the transit of a planet depends most directly on

A) the planet's mass.
B) the planet's density.
C) the planet's size.
D) the size of the planet's orbit.
E) the eccentricity of the planet's orbit.

Question 57

All planets orbit the Sun in the same direction (counterclockwise as viewed from above Earth's North Pole).

Question 58

What do models suggest make up the clouds on "hot Jupiters"?

A) ammonia
B) methane
C) water
D) rock dust
E) sodium

Question 59

All four of the giant outer planets-Jupiter, Saturn, Uranus, and Neptune-have rings.

Question 60

What would happen to the planets in a solar system where the central star did not have a strong wind?

A) One planet would grow to dominate all the others and gravitationally eject them out of the system.
B) All planets would continue to grow to large sizes but their orbits would be unchanged.
C) The gas in the solar nebula would create a drag on the planets and their orbits would migrate inwards.
D) The gas in the solar nebula would create a drag on the planets and their orbits would migrate outwards.
E) Nothing, the star does not affect the process of planet formation.

Question 61

All the planets in the solar system have at least one moon.

Question 62

A planet's size can be determined by observing its transit across a star.

Question 63

In the searches so far, only about 1 in 10 stars show evidence for planets around them.

Question 64

Within the frost line, planetesimals were composed entirely of rock and outside the frost line planetesimals were composed entirely of ice.

Question 65

Briefly summarize the differences between terrestrial and jovian planets.

Question 66

All the planets in the solar system rotate in the same direction as they orbit the Sun.

Question 67

Most of the planets discovered around other stars have masses comparable to the terrestrial planets in our own solar system.

Question 68

The Moon probably formed at the same time that Earth formed, rather like the formation of a double planet.

Question 69

Exceptions to a Scientific Theory? The solar nebula theory gives compelling explanations for the many regularities of our solar system. Nevertheless, the theory also claims to be perfectly consistent with the many exceptions to its basic predictions. This seems like a glaring contradiction in which the solar nebula theory would be consistent with any observed fact and hence not a scientific theory at all (why not?). Provide a deeper resolution to this apparent paradox by explaining how some of the basic exceptions in our own solar system are incorporated into the solar nebula theory. Is it really true that the theory would be consistent with any observed facts?

Question 70

Impacts were extremely common in the young solar system but are less common today.

Question 71

Earth's atmosphere resulted from the impact of icy planetesimals that originated in the outer regions of the Solar System.

Question 72

Predictions for Extra-solar Planets: What predictions does the solar nebula theory make regarding possible planetary systems surrounding other stars? Discuss at least two such predictions that have been strongly confirmed by observations. Explain how the detection of "hot Jupiter" extrasolar planets seemed to be a striking inconsistency with the solar nebula theory. Do you think astronomers were justified in modifying the solar nebula theory in the face of such evidence as opposed to discarding the theory altogether?

Question 73

A planet's density can be determined if it is observed to periodically transit in front of its parent star causing eclipses.

Question 74

Once a planet forms in a a disk-like nebula around a star, its orbit is fixed and will never change.

Question 75

In the 1800s, many people assumed that Venus would have tropical temperatures, but instead it is very hot. Explain why tropical temperatures would have made sense given what was known in the 1800s, and why Venus instead turns out to be very hot.

Question 76

The more massive planets in the solar system tend to be less dense than the lower mass planets.

Question 77

The Doppler technique for planet detection has found Earth like planets around nearby Sun-like stars

Question 78

Astronomers have discovered more extrasolar planets around other stars than the number of planets in our own Solar System.

Question 79

Based on our theory of how our own solar system formed, we would expect that other solar systems would be quite common.

Question 80

The Solar Nebula as a Scientific Theory: You are describing the solar nebula theory to a friend. You point out that it provides an explanation for the regular motion in our solar system, the division of the planets into terrestrial and jovian types, and an explanation for the origin and nature of comets and asteroids. Your friend agrees that this is all very nice, but that it seems that the solar nebula theory fails the basic criteria for a scientific theory, to make predictions about the natural world that can be observationally tested. In her opinion, all the solar nebula theory does is explain known facts, albeit in a compelling and economical way. How would you answer your friend and make the case that the solar nebula theory is indeed a scientific theory that has passed many observational tests? Can you think of any predictions that the solar nebula theory has made that were confirmed only within the last decade or so?