Deck 6: The Birth and Evolution of Planetary Systems

Question 1

Astronomers believe that Venus was created with the thick atmosphere it currently has.

Answer 1

False

Question 2

The plane of an accretion disk is always perpendicular to the axis of rotation of the interstellar cloud out of which it forms.

Answer 2

True

Question 3

Conservation of angular momentum states that as a cloud of interstellar gas and dust collapses,the velocity of the particles increases.

Answer 3

True

Question 4

The Solar System was formed when a passing star tidally extruded mass from the forming Sun.

Question 5

The angular momentum of a planet depends on its mass and its distance from the Sun.

Question 6

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,40 AU,what would its rotation period be?

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

Question 7

The temperature gradient in accretion disks surrounding protostars is due in part to the fact that material closer to the protostar has converted less of its kinetic energy into thermal energy.

Question 8

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

Question 9

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

Question 10

To date astronomers have not yet detected Earth-size planets around normal stars.

Question 11

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

A) The early Solar System must have been flat.
B) The material from which the planets formed must have been swirling about the Sun in the same direction.
C) The first fragments started out small and grew in size over time.
D) The composition of gases varied between the inner Solar System and the outer Solar System.

Question 12

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) 10
B) 26 thousand
C) 36 million
D) 50 billion

Question 13

All planets orbit the Sun in the same direction.

Question 14

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) 10 percent
C) 5 percent
D) < 1 percent

Question 15

In the smaller 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 16

Our Solar System is likely unique among the stars in our Galaxy.

Question 17

Over 330 extra-solar planets have been detected by direct imaging of the planets.

Question 18

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 6,000 km,and 1 AU is .

A) 70
B) 640
C) 25,000
D) 4 million

Question 19

As the planets were forming,the Sun was shining due to nuclear fusion on its surface.

Question 20

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

Question 21

Why do outer planets like Jupiter have huge 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 solar winds blew away their original gaseous atmospheres.
D) Frequent early collisions by comets with the inner planets caused most of their original atmospheres to dissipate.

Question 22

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.

Question 23

Conservation of angular moment 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.

Question 24

What is the age of our solar system?

A) 4.5 billion years
B) 4.5 million years
C) 13.7 billion years
D) 13.7 million years

Question 25

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.

Question 26

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) A small amount of it
D) Barely any at all

Question 27

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

A) metal.
B) silicate.
C) rock.
D) ice.

Question 28

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

A) It is converted into thermal energy,heating the disk.
B) It is converted into light energy,giving off a flash of light upon impact.
C) It is converted into potential energy as the gas plows through the disk and comes out the other side.
D) It simply dissipates.

Question 29

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.

Question 30

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.

Question 31

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

A) its mass.
B) its temperature.
C) the distance from the star that it orbits.
D) All of the above

Question 32

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 over.

Question 33

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 surrounding the protostar.
B) the merger of two large planetesimals.
C) an eruption of material from the protostar.
D) materials condensing out of the solar wind.

Question 34

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;thermal
C) kinetic;potential
D) potential;total

Question 35

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) All of the above

Question 36

The primary atmospheres of the planets are made mostly of

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

Question 37

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 Jovian planets would form around the protostar.
D) Only terrestrial planets would form around the protostar.

Question 38

The atmosphere of which of these planets is primary,as opposed to secondary,in origin?

A) Venus
B) Earth
C) Saturn
D) Mars

Question 39

Consider four spheres of equal mass.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.

Question 40

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

A) No,its composition is too different from stars for it to become one.
B) Yes,but it cooled off before it could become a star.
C) No,it would have to be at least 80 times more massive.
D) Yes,it is in the process of becoming a star in the near future.

Question 41

What is the best method to use to detect Earth-sized extra-solar planets with the telescopes and instrumentation that exist today?

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

Question 42

Astronomers have used radial velocity monitoring to discover

A) extra-solar 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) extra-solar planetary systems that contain more than one planet.

Question 43

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

Question 44

What does conservation of angular momentum mean?

Question 45

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 46

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

A) 1 Jupiter mass.
B) 13 Jupiter masses.
C) 42 Jupiter masses.
D) 80 Jupiter masses.

Question 47

When astronomers began searching for extra-solar 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 radius 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.

Question 48

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

Question 49

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 50

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) It is not massive enough.
D) It is tidally locked to Earth.

Question 51

Why have astronomers 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.

Question 52

An observer 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) convection on the Sun's surface.
D) the sunspot cycle.

Question 53

What is the difference between refractory and volatile materials?

Question 54

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

Question 55

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

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

Question 56

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

Question 57

Most planets currently found around other stars are

A) of rocky composition like the Earth.
B) comparable in mass to Neptune or more massive.
C) less massive than Mars.
D) located at distances much larger than Jupiter's distance from the Sun.

Question 58

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

A) the planet must pass directly in front of the star.
B) the planet must have a rocky composition.
C) the star must be very dim.
D) the star must be moving with respect to us.

Question 59

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

A) losing orbital angular momentum.
B) colliding with another planet.
C) slowly accreting large amounts of gas and increasing their gravitational pull.
D) losing their gas due to evaporation.

Question 60

Which of the following is FALSE?

A) Over 330 extra-solar planets have been discovered to date from radial velocity surveys.
B) The most common type of extra-solar planet found to date has a few times the mass of Jupiter and lies within a few AU from its parent star.
C) No extra-solar planets have been imaged directly to date;all have all been found by indirect methods.
D) A star can brighten significantly due to gravitational lensing when a planet that orbits it passes directly in front of the star.

Question 61

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

Question 62

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

Question 63

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

Question 64

Approximately how massive are nearly all the extra-solar planets that have been discovered thus far,and how is this related to the way in which we detect them?

Question 65

Explain how astronomers use the Doppler effect to detect the presence of extra-solar planets.

Question 66

Explain why most of the extra-solar planets astronomers have detected are so-called "hot Jupiters."

Question 67

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