Deck 5: The Formation of Stars and Planets

Question 1

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, and 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.

Answer 1

Valles Marineris on Mars is a huge scar, many times deeper than the Grand Canyon, and spans one-fourth the circumference of the planet.

Question 2

You record the spectrum of a star and find that the calcium absorption line,whose rest wavelength is 393.3 nm,has an observed wavelength of 394.0 nm.What is the radial velocity of this star?

A) 500 km/s
B) 50 km/s
C) 5 km/s
D) 0.5 km/s

Answer 2

500 km/s

Question 3

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

Answer 3

a small amount of it

Question 4

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 5

Three stars are found to have been formed from a molecular cloud.How many high density fragments must have existed in the cloud prior to star formation?

A) exactly three
B) only one
C) three or more
D) none

Question 6

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

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

Question 7

Volatile and refractory materials differ in their:

A) melting temperatures.
B) density at a given temperature.
C) composition.
D) all of the above.

Question 8

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 9

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

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

Question 10

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 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 over.

Question 12

What happens to the gravitational 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 13

The Moon probably formed:

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

Question 14

You are driving on the freeway when a police officer records a shift of -7 nm when he hits you with a radar gun that operates at a wavelength of 0.1 m.How fast were you going?

A) 47 mph
B) 83 mph
C) 21 mph
D) 65 mph

Question 15

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.

Question 16

Examine the figure below.What causes molecular clouds to collapse?

A) conservation of charge
B) self-gravity
C) thermal energy
D) radiation

Question 17

The increasing temperature of the core of a collapsing cloud of gas is due to:

A) radiation.
B) collisions between gas molecules.
C) increased spin rate of the cloud.
D) fragmentation of the core.

Question 18

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 19

What conservation law explains why the skater spins faster when her arms are pulled in?

A) conservation of charge
B) conservation of energy
C) conservation of angular momentum

Question 20

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 21

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.

Question 22

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

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 23

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 24

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 25

Explain why an ice-skater spins faster when she pulls her arms in compared to when her arms are stretched straight out.

Question 26

Explain the process of protostar formation shown in the figure below.

Question 27

What is the best method commonly used to detect Earth-sized extrasolar planets with the telescopes and instrumentation that exist today?

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

Question 28

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

Question 29

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 30

For a star that lies in the plane of Earth's orbit around the Sun,how does the observed wavelength of a hydrogen absorption line in its spectrum change in wavelength (if at all)with the time of year?

Question 31

The Doppler shift can be used to determine the ________ of an object.

A) energy
B) temperature
C) radial velocity
D) no radiation

Question 32

Why are most of the planets composed of refractory materials found in the inner solar system?

A) Refractory material existed only in the inner protoplanetary disk.
B) Planetary bodies can only be formed from refractory materials.
C) The temperature of the inner protostellar accretion disk was too high for volatile components to remain solid.
D) All the bodies composed of refractory materials in the outer disk migrated to the inner disk.

Question 33

Examine the figure below.What method of looking for extrasolar planets requires the planet to pass in front of the star?

A) radial velocity method
B) transit method
C) direct imaging

Question 34

Examine the figure below.Describe the conservation laws at play during the formation of a protostar and the accretion disk.

Question 35

Astronomers hypothesize 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 because of evaporation.

Question 36

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

A) These planets must have formed at a 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 37

Suppose you observe a star emitting a certain emission line of helium at 584.8 nm.The rest wavelength of this line is 587.6 nm.How fast is the star moving? Is it moving toward you or away from you?

Question 38

What does conservation of angular momentum mean?

Question 39

Why do the gas motions of an accretion disk move smaller particles more easily than larger particles?

A) The larger particles tend to be smoother and therefore more aerodynamic.
B) The smaller particles are more dense.
C) The larger particles are more dense.
D) Forces applied to smaller less massive objects result in larger accelerations.

Question 40

How does gravitational energy get converted to thermal energy in a gas cloud?

Question 41

How does the size of planets in the solar system relate to the constituents of their atmospheres?

Question 42

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

Question 43

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

Question 44

Briefly explain the five different observational methods we use to detect extrasolar planets.

Question 45

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

Question 46

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

Question 47

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

Question 48

What is the difference between refractory and volatile materials?

Question 49

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

Question 50

What processes contributed to the development of Earth's secondary atmosphere?