Deck 7: The Birth and Evolution of Planetary Systems

Question 1

Consider a small parcel of gas in the cloud out of which the Sun formed that was initially located in the accretion disk at a distance of 10 AU from the Sun and rotating around it with a speed of 10 km/s.If this parcel of gas eventually found its way to a distance of 1 AU from the Sun without changing its orbital angular momentum,then what would be its new rotation speed?

A)100 km/s
B)0.1 km/s
C)0.001 km/s
D)10 km/s
E)1,000 km/s

Answer 1

100 km/s

Question 2

Current technology is sensitive enough to detect some extrasolar planets by a dip in brightness of the parent star as the planets pass between us and it.

Answer 2

True

Question 3

The temperature gradient in the accretion disk surrounding a protostar is due in part to the fact that material closer to the protostar has converted less of its kinetic energy into thermal energy compared to materials farther away.

Answer 3

False

Question 4

Inside a solar nebula,as smaller particles collide and stick together,forming larger particles,their self-gravity prevents them from breaking apart,regardless of the strength of the collision.

Question 5

All planets orbit the Sun in the same direction.

Question 6

What is the ratio of the orbital angular momentum of the Earth compared to its spin angular momentum? Note that the Earth has a radius of 6 × 10⁶ m,and 1 AU is 1.5 × 10¹¹ m.

A)1
B)70
C)640
D)25,000
E)4.3 × 10⁶

Question 7

The maximum mass of a planet is approximately 0.08 times the mass of the Sun.

Question 8

The fact that Jupiter's radius is contracting at a rate of 1 mm per year results in:

A)Jupiter's rotation rate slowing down with time
B)Jupiter's shape being noticeably oblate
C)Jupiter moving slightly farther from the Sun with time
D)Jupiter radiating more heat than it receives from the Sun
E)Jupiter having a strong magnetic field

Question 9

If a collapsing interstellar cloud formed only a protostar without an accretion disk around it,what would happen?

A)The forming protostar would be significantly less massive than it would have been otherwise.
B)The forming protostar would be rotating too fast to hold itself together.
C)Only giant planets would form around the protostar.
D)Only terrestrial planets would form around the protostar.
E)More planets would form around the protostar.

Question 10

Astronomers believe that Venus initially formed with the thick atmosphere,primarily made of carbon dioxide,which it currently has.

Question 11

According to the conservation of angular momentum,if an ice skater starts spinning with her arms out wide,then slowly pulls them close to her body,this will cause her to:

A)spin faster
B)spin slower
C)maintain a constant rate of spin
D)fall down

Question 12

Planets like Earth are found closer to the Sun than planets like Jupiter.

Question 13

Approximately how much mass was there in the protoplanetary disk out of which the planets formed,compared to the mass of the Sun?

A)50 percent
B)25 percent
C)10 percent
D)5 percent
E)< 1 percent

Question 14

Which of the following is NOT a characteristic of the early Solar System,based on current observations?

A)The early solar nebula must have been flattened.
B)The material from which the planets formed was swirling about the Sun in the same average rotational direction.
C)The first objects to form started out small and grew in size over time.
D)The initial composition of the solar nebula varied between its inner and outer regions.
E)Temperatures decreased with increasing distance from the Sun.

Question 15

Our Solar System is the only planetary system in our galaxy.

Question 16

Conservation of angular momentum slows a cloud's collapse:

A)equally in all directions
B)only when the cloud is not rotating initially
C)mostly along directions perpendicular to the cloud's axis of rotation
D)mostly at the poles that lie along the cloud's axis of rotation
E)to a complete stop

Question 17

Hundreds of extrasolar planets have been detected by direct imaging of the planets.

Question 18

What is the ratio of the orbital angular momentum of Jupiter to its spin angular momentum? Jupiter's orbit has a semimajor axis of 5 AU and period of 12 years,and Jupiter has a rotation period of 0.4 day and a radius of 70,000 km.

A)650,000
B)26,000
C)920
D)38
E)4.5

Question 19

If an interstellar cloud having a diameter of 10¹⁶ m and a rotation period of a million years were to collapse to form a sphere that had the diameter of our Solar System,approximately 40 AU,what would its rotation period be? Assume the cloud's total mass and angular momentum did not change.

A)1 million years
B)600 years
C)1 year
D)6 years
E)4 months

Question 20

In protoplanetary environments,the plane of an accretion disk is perpendicular to the axis of rotation of the interstellar cloud out of which it forms.

Question 21

Why do the terrestrial planets have a much higher fraction of their mass in heavy chemical elements (as opposed to lighter chemical elements)than the giant planets?

A)Terrestrial planets are low in mass and high in temperature,thus their lighter chemical elements eventually escaped to the outer reaches of the Solar System.
B)The heavier elements in the forming solar nebula sank to the center of the Solar System,thus the inner terrestrial planets formed mostly from heavy chemical elements.
C)The giant planets were more massive than terrestrial planets,and the giant planets preferentially pulled the lighter elements from the inner to the outer Solar System.
D)Terrestrial planets formed much earlier than giant planets before the hydrogen and helium had a chance to cool and condense onto them.
E)Terrestrial planets are colder and thus more massive chemical elements condensed on then than the giant planets.

Question 22

Which of the following is NOT considered evidence of cataclysmic impacts in the history of our Solar System?

A)Uranus is "tipped over" so that it rotates on its side.
B)Valles Marineris on Mars is a huge scar,many times deeper than the Grand Canyon,which spans one-fourth the circumference of the planet.
C)Mercury has crust that has buckled on the opposite side of an impact crater.
D)Mimas has a crater whose diameter is roughly one-third of the Moon's size.
E)Mercury,Earth's Moon,and many other small bodies are covered with many impact craters.

Question 23

Comets and asteroids are:

A)other names for moons of the planets
B)primarily located within 1 AU of the Sun
C)all more massive than Earth's Moon
D)material left over from the formation of the planets
E)other names for meteors

Question 24

What sets the temperature of the pocket of gas in a protoplanetary disk?

A)its distance from the forming star
B)how much kinetic energy was converted to heat
C)how much radiation from the forming star shines on the gas
D)a combination of all three of the above

Question 25

What is the most important factor in determining whether or not a planet will be rocky like terrestrial planets or gaseous like giant planets?

A)the time at which the planet forms
B)the planet's radius
C)the planet's distance from the Sun
D)whether the planet has moons
E)the planet's internal temperature

Question 26

The atmosphere of which of these Solar System bodies is primary,as opposed to secondary,in origin?

A)Venus
B)Earth
C)Saturn's moon Titan
D)Saturn
E)Mars

Question 27

When you push your palms together and rub them back and forth,you are demonstrating one way of converting _________ energy into _________ energy.

A)potential;thermal
B)kinetic;potential
C)thermal;kinetic
D)kinetic;thermal
E)potential;total

Question 28

Consider four spheres of equal mass and size.Which has the most potential energy?

A)a sphere on the top shelf of a bookshelf
B)a sphere rolling on the floor at the base of the bookshelf
C)a sphere sitting at rest on the floor at the base of the bookshelf
D)a sphere on the middle shelf of a bookshelf
E)a sphere that fell from the top shelf to the floor

Question 29

What happens to the kinetic energy of gas as it falls toward and eventually hits the accretion disk surrounding a protostar?

A)It is immediately converted into photons,giving off a flash of light upon impact.
B)It is converted into thermal energy,heating the disk.
C)It is converted into potential energy as the gas plows through the disk and comes out the other side.
D)It becomes the kinetic energy of the orbit of the gas in the accretion disk around the protostar.
E)It disappears into interstellar space.

Question 30

The primary atmospheres of the planets are made mostly of:

A)carbon and oxygen
B)hydrogen and helium
C)oxygen and nitrogen
D)iron and nickel
E)nitrogen and argon

Question 31

Two competing models of the formation of giant gaseous planets suggest they form either from gas accreting onto a rocky core or from:

A)fragmentation of the accretion disk that surrounds the protostar
B)the merger of two large planetesimals
C)planets stolen from another nearby protostar
D)materials condensing out of the solar wind
E)an eruption of material from the protostar

Question 32

The solid form of a volatile material is generally referred to as a(n):

A)metal
B)silicate
C)ice
D)rock
E)refractory material

Question 33

How much material in an accretion disk goes into forming the planets,moons,and smaller objects?

A)most of it
B)roughly half of it
C)none;these objects were not formed in the accretion disk
D)a small amount of it

Question 34

What is the age of our Solar System?

A)4.6 billion years
B)4.6 million years
C)13.7 trillion years
D)13.7 billion years
E)13.7 million years

Question 35

Whether or not a planet is composed mostly of rock or gas is set by:

A)its mass
B)its temperature
C)its distance from the star when it formed
D)a combination of all three of the above

Question 36

What prevented the Moon from maintaining any atmosphere with which it originally formed?

A)It repeatedly collided with planetesimals.
B)It is too close to the Sun.
C)The solar wind blew it away.
D)It is not massive enough.
E)It is tidally locked to Earth.

Question 37

Was it ever possible (or is it currently possible)for Jupiter to become a star?

A)Yes,it is in the process of becoming a star in the near future.
B)Yes,but it cooled off before it could become a star.
C)No,it would have to be at least 13 times more massive.
D)No,its composition is too different from stars for it to become one.
E)No,it used to be massive enough,but the solar wind has blown off too much of its mass.

Question 38

Why do the outer giant planets have massive gaseous atmospheres of hydrogen and helium while the inner planets do not?

A)These gases were more abundant in the outer regions of the accretion disk where the outer planets formed.
B)The outer planets grew massive quickly enough to gravitationally hold on to these gases before the solar wind dispersed the accretion disk.
C)The inner planets were too close to the Sun,and the solar wind blew away their original gaseous atmospheres.
D)Frequent early collisions by comets with the inner planets caused most of their original atmospheres to dissipate.
E)Temperatures were too high in the region of the Solar System that contains the inner planets.

Question 39

The Moon probably formed:

A)out of a collision between the Earth and a Mars-sized object
B)when the Earth's gravity captured a planetesimal
C)when the accretion disk around the Earth fragmented
D)when planetesimals collided to form a more massive object
E)when a piece of Earth broke off and entered orbit

Question 40

The difference in composition between the giant planets and the terrestrial planets is most likely caused by the fact that:

A)the giant planets are much larger
B)only the terrestrial planets have iron cores
C)the terrestrial planets are closer to the Sun
D)the giant planets are made mostly of carbon
E)only small differences in chemical composition existed in the solar nebula

Question 41

What is the best method to detect Earth-sized exoplanets with the telescopes and instrumentation that exist today?

A)Doppler shift is the best method.
B)Transit is the best method.
C)Microlensing is the best method.
D)Direct imaging is the best method.
E)All of the above methods can be used.

Question 42

Earth-sized planets have been found using the _________ method(s).

A)Doppler shift
B)transit and Doppler shift
C)microlensing
D)direct imaging
E)transit

Question 43

If an astronomer on a planet orbiting a nearby star observed the Sun when Neptune was transiting in front of the Sun,how would the Sun's brightness change? Note that the radius of Neptune is 2.5 × 10⁷ m.

A)The Sun's brightness would decrease by 0.1 percent.
B)The Sun's brightness would increase by 0.1 percent.
C)The Sun's brightness would increase by 1 percent.
D)The Sun's brightness would decrease by 1 percent.
E)The Sun's brightness would not change at all.

Question 44

Have astronomers detected any Earth-sized planets around normal stars yet?

A)Yes,the Kepler spacecraft is just starting to find them.
B)Yes,although the ones detected lie much closer to their stars than we do to ours.
C)Yes,although the ones detected lie much farther from their stars than we do from ours.
D)No,we do not have the technology to detect such low-mass planets yet.
E)No;although we have the technology to detect low-mass planets,we haven't found any others yet.

Question 45

Detecting a planet around another star using the transit method is difficult because the:

A)planet must pass directly in front of the star
B)planet must have a rocky composition
C)star must be very dim
D)star must be moving with respect to us
E)planet's orbital period is usually longer than 1 month

Question 46

Which is NOT a scientific goal of NASA's Kepler mission?

A)Finding Earth-sized planets is not a goal.
B)Finding rocky planets is not a goal.
C)Finding Earth-sized planets that could have liquid water is not a goal.
D)Finding intelligent life on other planets is not a goal.
E)All the above are goals of the Kepler mission.

Question 47

An observer located outside our Solar System,who monitors the velocity of our Sun over time,will find that its velocity varies by ±12 m/s over a period of 12 years,because of:

A)Jupiter's gravitational pull
B)Earth's gravitational pull
C)variations in its brightness
D)convection on the Sun's surface
E)the sunspot cycle

Question 48

Astronomers have used radial velocity monitoring to discover:

A)extrasolar planetary systems that are similar to our own solar system
B)Earth-sized planets around other stars
C)Earth-sized planets at distances of 10 AU from their parent stars
D)extrasolar planetary systems that contain more than one planet
E)all of the above

Question 49

The Kepler mission is designed to search for extrasolar planets using the _________ method.

A)Doppler shift
B)transit
C)microlensing
D)direct imaging

Question 50

Most planets currently found around other stars are:

A)rocky in composition like terrestrial planets
B)2 to 10 M_Earth,which is smaller than Neptune
C)2 to 10 M_Jupiter
D)located at distances much larger than Jupiter's distance from the Sun
E)similar in mass to the Earth

Question 51

Which method can be used to determine the radius of an extrasolar planet?

A)Doppler shift can be used.
B)Transit can be used.
C)Microlensing can be used.
D)Direct imaging can be used.
E)None of these methods are able to do this.

Question 52

Why have astronomers using the radial velocity method found more Jupiter-sized planets at a distance of 1 AU around other stars than Earth-sized planets?

A)A Jupiter-sized planet occults a larger area than an Earth-sized planet.
B)A Jupiter-sized planet exerts a larger gravitational force on the star than an Earth-sized planet,and the Doppler shift of the star is larger.
C)A Jupiter-sized planet shines brighter than an Earth-sized planet.
D)Earth-sized planets are much rarer than Jupiter-sized planets.
E)Actually,the planets found at these distances have all been Earth sized.

Question 53

Which of the following is FALSE?

A)The masses of exoplanets can be determined using the radial velocity technique.
B)Most of the exoplanets detected to date have masses that are between 2 and 10 M_Earth.
C)Some exoplanets have been found in the habitable zone around their stars.
D)Using the transit technique,the Kepler satellite has detected rocky planets.
E)No images of exoplanets have been obtained because they are too far away.

Question 54

Consider a star that is more massive and hotter than the Sun.For such a star,the habitable zone would:

A)be located inside 1 AU
B)be located outside 1AU
C)not exist at any radii
D)exist at every radii

Question 55

Which of the following is FALSE?

A)Hundreds of extrasolar planets have been discovered to date from radial velocity surveys.
B)The most common types of extrasolar planets found to date have masses 10 times the mass of Jupiter and lie within 5 AU from their parent star.
C)Some planetary systems have been found that contain multiple planets.
D)A star can brighten significantly due to gravitational lensing when a planet that orbits it passes directly in front of the star.
E)The Kepler mission has begun to find terrestrial planets similar in size to Earth.

Question 56

Explain the nebular hypothesis,and describe two observations that support it.

Question 57

The borderline between the most massive planet and the least massive brown dwarf occurs at:

A)4 Jupiter masses
B)13 Jupiter masses
C)120 Jupiter masses
D)80 Jupiter masses
E)45 Jupiter masses

Question 58

When astronomers began searching for extrasolar planets,they were surprised to discover Jupiter-sized planets much closer than 1 AU from their parent stars.Why is this surprising?

A)These planets must have formed at larger radii where temperatures were cooler and then migrated inward.
B)Jupiter-sized,rocky planets were thought to be uncommon in other solar systems.
C)These planets must be the remnants of failed stars.
D)Earth-like planets must be rarer than Jupiter-sized planets in other solar systems.
E)It is different than in our Solar System.

Question 59

Which property of an extrasolar planet CANNOT be determined using the Doppler effect?

A)orbital period
B)orbital distance
C)orbital speed
D)mass
E)radius

Question 60

Astronomers believe that the "hot Jupiters" found orbiting other stars must have migrated inward over time:

A)by slowly accreting large amounts of gas and increasing their gravitational pull
B)by losing their gas due to evaporation
C)by losing orbital angular momentum
D)after colliding with another planet
E)after a close encounter between their star and another star

Question 61

The primordial atmosphere of the Earth consisted of what type of chemical elements and from where did it originate? What chemical elements did the secondary atmosphere of the Earth consist of and from where did it originate?

Question 62

Briefly explain the four different observational methods we use to detect extrasolar planets.Which has detected the largest number of extrasolar planets to date?

Question 63

Why might a newly discovered comet contain clues to the composition of the early solar nebula?

Question 64

Explain the two primary reasons why the inner solar nebula was hotter than the outer solar nebula.

Question 65

Why did the planetesimals in the asteroid belt never coalesce into a planet?

Question 66

What is the difference between refractory and volatile materials?

Question 67

What evidence do we have that the accretion disk that formed the Solar System was initially very centrally condensed?

Question 68

Approximately how massive are most of the extra-solar planets that have been discovered using the Doppler effect,and which planet in our solar system is similar in mass? Why is the Doppler effect method more likely to find massive (rather than low-mass)planets and planets that are close to their stars?

Question 69

Explain why an accretion disk forms around a protostar when an interstellar cloud collapses.

Question 70

Compare the orbital angular momentum of the Earth and Jupiter.Which is larger and by how much? (Note that Jupiter's mass is 318 times that of the Earth;the semimajor axis of Jupiter's orbit is 5.2 AU;and Jupiter's orbital period is 12 years. )

Question 71

How did the formation of our Moon differ from the formation of the Galilean moons of Jupiter?

Question 72

Explain why there is a significant amount of methane and ammonia in the atmospheres of Uranus and Neptune but not nearly as much in the atmospheres of Jupiter and Saturn.

Question 73

What does conservation of angular momentum mean?

Question 74

How do astronomers explain the basic difference in composition between the inner planets and the outer planets?

Question 75

Explain how astronomers use the Doppler effect to detect the presence of extrasolar planets.

Question 76

Explain why most of the extrasolar planets that astronomers first detected were so-called "hot Jupiters."

Question 77

Explain why astronomers believe that the formation of planets is a natural by-product of star formation.