Deck 10: Other Planetary Systems: the New Science of Distant Worlds

Question 1

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

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

Answer 1

B

Question 2

As of the time of the publication of the textbook, how many planets have been discovered using the Doppler method?

A)70
B)7
C)7000
D)700

Answer 2

D

Question 3

Planets detected via the Doppler technique have been mostly

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

Answer 3

E

Question 4

Direct detection of an extrasolar planet means .

A)acquiring images or spectra of the planet
B)seeing the planet with the naked eye
C)observing the planet's effect on its host star
D)sending a space probe to the planet

Question 5

Most of the planets discovered around other stars using the Doppler technique

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

Question 6

Two stars with about the same mass are found to have transiting planets with similar semi- major axes. Star 1 exhibits a Doppler shift twice as large as Star 2. What can we determine about these two systems?

A)The planet around Star 2 has a thicker atmosphere than the planet around Star 1.
B)The planet around Star 1 has a thicker atmosphere than the planet around Star 2.
C)The planet around Star 2 is more massive than the planet around Star 1.
D)The planet around Star 1 is more massive than the planet around Star 2.

Question 7

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

A)about two thousand
B)tens of thousands
C)ten
D)about two hundred
E)millions

Question 8

At least 70% of stars have planets. How many planets can astronomers reasonably claim exist in the Milky Way galaxy?

A)at least 1 trillion
B)at least 70 billion
C)at least 3000
D)at least 8

Question 9

You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?

A)The planet must have a mass about the same as the mass of Jupiter.
B)The planet must be closer to the star than Earth is to the Sun.
C)You do not have enough information to say anything at all about the planet.
D)The planet must be farther from the star than Neptune is from the Sun.

Question 10

How can astronomers currently determine the temperature of an extrasolar planet?

A)estimate the temperature based on the planet's distance from the star
B)measure the drop in total infrared light when the planet passes behind the star from our perspective
C)use spectroscopy of the planet to identify the wavelength at which its emission peaks
D)A and B
E)B and C

Question 11

Which two quantities need to be measured in order to determine the density of a planet?

A)mass
B)atmospheric composition
C)radius
D)A and B
E)A and C

Question 12

What mechanism explains the presence of "hot Jupiters" around many other stars?

A)planetary migration caused by gravitational interactions between the planet and disk
B)evaporation of the disk by the stellar wind removes gas that was holding the planet at a large radius
C)rapid formation of the gas giant from evaporated rock and metal at the inner disk edge
D)gravitational attraction by terrestrial planets that formed at small radii attract the giant planets inward

Question 13

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

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

Question 14

According to the nebular theory, where should jovian planets form?

A)within the inner few AU of the disk, where only rocks and metals can condense
B)in the cold outer regions of the disk, where rocks, metals, and ices can condense
C)at the inner edge of the planet forming disk, where even metal and rock evaporate

Question 15

What mechanism likely accounts for whether a large icy planetesimal becomes a "water world" or a gas giant?

A)the timing of when the stellar wind blows away the remaining gas of the planet forming nebula
B)the migration of larger planets through the disk
C)the presence of other planets to make its orbit highly eccentric
D)the amount of heavy metals initially present in the disk

Question 16

This figure shows the orbital periods and radii of all planet candidates identified from Kepler data as of early 2013. Which of the following size planets were most detected?

A)planets less than 1 Earth radius in size
B)planets greater than 10 Earth radii in size
C)planets between 1 Earth radius and 4 Earth radii in size
D)planets between 4 Earth radii and 10 Earth radii in size

Question 17

Consider a star with 2 planets. The mass of planet A is the same as the mass of planet B. The orbit of Planet A is on average, closer to the star than the orbit of Planet B. Which of the following statements is true?

A)Planet A moves with the same speed as Planet B.
B)Planet A is, on average, moving faster than Planet B.
C)The relative orbital speeds depend on the masses of the planets.
D)Planet A is, on average, moving slower than Planet B.

Question 18

At least _ % of stars host at least one planet.

A)1
B)30
C)10
D)70

Question 19

What is the chief difficulty in attempting to detect planets around other stars?

A)Even the largest planets are typically at least a factor of 10 times smaller than their host stars.
B)Planets do not emit visible light. They are typically at least a billion times fainter than their host stars.
C)Planets do not glow in the infrared, so infrared telescopes cannot be used to study them, either.
D)A and B
E)A, B, and C

Question 20

The Doppler technique can be used to estimate the semimajor axis of a planet's orbit by

A)measuring the speed at which the star orbits the mutual center- of- mass of the star and planet, and using Newton's theory of gravity.
B)measuring the amount by which the starlight is reduced when the planet transits.
C)measuring the time it takes for the star's line- of- sight velocity to cycle from peak to peak, and using Newton's version of Kepler's Third law.
D)measuring the asymmetries in the velocity curve.

Question 21

You are measuring how velocity changes with time of two stars like the Sun in order to detect their planets. Both stars have a velocity curve with a period of 2 years, but the maximum size (peak- to- peak amplitude)of the velocity curve of star A is 100 km/s, and for star B it is 200 km/s. What causes this difference? Assume the planets are named after their stars.

A)Planet A is more massive than Planet B.
B)Planet A is less massive than Planet B.
C)Planet A is farther from Star A than Planet B is to Star B.
D)Planet A is closer to Star A than Planet B is to Star B.
E)Not possible to say, since you're measuring the velocity curve of the stars, not the planets.

Question 22

According to Kepler results in mid- 2013, what fraction of stars host an Earth- size planet?

A)about 15%
B)about 100%
C)about 70%
D)about 20%

Question 23

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

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

Question 24

A star is seen to have two transiting planets. Planet 1 transits every 3 months, and Planet 2 transits every 15 months. What can we infer about their orbits? (Hint: Review the use of Newton's version of Kepler's Third law from Ch. 4)

A)Planet 2's semimajor axis is about 3 times smaller than Planet 1's.
B)Planet 2's semimajor axis is about 3 times larger than Planet 1's.
C)Planet 2's semimajor axis is about 5 times larger than Planet 1's.
D)Planet 2's semimajor axis is about 5 times smaller than Planet 1's.

Question 25

As of the time of the publication of the textbook, how many planet candidates have been discovered using the transit method?

A)about 10
B)a few thousand
C)a few hundred
D)tens of thousands

Question 26

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

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

Question 27

How does the theory of planetary migration in disks possibly account for the highly eccentric orbits discovered for some extrasolar planets?

A)When migrating planets pass close enough for a gravitational encounter, one may be flung from the system while the other is shifted to a highly elliptical orbit.
B)When migrating planets collide, they would move onto more eccentric orbits.
C)When a planet migrates onto the surface of the star, the additional stellar mass would disrupt the orbits of the remaining planets.
D)A migrating planet would create waves in the planet forming disk, which would in turn lead to the formation of planets on highly elliptical orbits.

Question 28

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 this century.
D)about two decades ago.
E)at the turn of last century.

Question 29

How can astronomers measure the composition of an extrasolar planet's atmosphere?

A)by measuring the composition of the host star; the planet must have formed from the same initial material
B)by comparing spectra for when the planet is in transit or eclipse with spectra taken at other times
C)by measuring how brightly the planet glows in infrared light
D)by measuring the Doppler shift of the host star

Question 30

What is astrometry?

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

Question 31

What are the two primary methods by which planets have been found around other stars in our galaxy? I)Direct images in visible and infrared light
II)Indirectly by detecting the motion of the host star
III)Indirectly by measuring the drop in brightness of the host star when the planet crosses our line of sight

A)I and II
B)II and III
C)I and III

Question 32

Which of the following statements about the accelerations and gravitational forces between a planet and a star is true?

A)Acceleration is equal and opposite; the planet feels more force more than the star.
B)Forces are equal and opposite; the planet is accelerated more than the star.
C)Forces are equal and opposite; the star is accelerated more than the planet.
D)Accelerations and forces are both equal and opposite.
E)Acceleration is equal and opposite; the star feels more force more than the planet.

Question 33

The transit method of planet detection works best for

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

Question 34

What is a so- called "hot Jupiter"?

A)a planet with a mass and composition similar to what we would expect if Jupiter were hotter
B)a planet with a mass similar to Jupiter but very close to the central star and therefore hot
C)a Jupiter mass planet orbiting a star that is more massive and hotter than the Sun
D)a planet with a mass similar to Jupiter but composition similar to Mercury

Question 35

What type of observation can astronomers use to measure the composition of extrasolar planet atmospheres?

A)measurements of the host star's velocity throughout an orbital cycle
B)comparisons of spectra when planets are in front of or are eclipsed by their host stars
C)combination of a transit observation and a Doppler shift measurement
D)measurement of how frequently the planet blocks the host star's light

Question 36

The Doppler technique can be used to measure the eccentricity of a planet's orbit by

A)measuring the time it takes for the star's line- of- sight velocity to cycle from peak to peak, and using Newton's version of Kepler's Third law.
B)measuring the amount by which the starlight is reduced when the planet transits.
C)measuring the asymmetries in the velocity curve.
D)measuring the speed at which the star orbits the mutual center- of- mass of the star and planet, and using Newton's theory of gravity.

Question 37

How can astronomers measure the period of a planet's orbit?

A)by measuring the time between peaks in the star's velocity curve
B)by measuring the time between repeated transits
C)by timing the cycle of small changes in a stars position on the sky
D)all of the above

Question 38

Consider two main sequence K- stars of equal mass. Each star has been measured for a periodic wobble in its velocity curve, with one having a period of 1 month and the other having a period of 2 months. Which star has the closest planet (the planet with the smallest orbit)?

A)the star with a period of 1 month
B)the star with a period of 2 months
C)The planet orbit sizes can't be determined from the information provided.

Question 39

In order to be able to directly see the Sun's motion due to Jupiter's gravity, an observer at a distance of 30 light- years would need to be able to measure changes in its position of _.

A)0)05 arcsecond
B)0)5 arcsecond
C)0)0005 arcsecond
D)0)005 arcsecond

Question 40

What could happen in planetary systems where the nebular gas is quickly disbursed?

A)Large ice- rich planetesimals would not be able to gather hydrogen and helium and become gas giants.
B)Many planets would be destroyed by migration onto the central star.
C)The only planets would be more massive than Jupiter.
D)No terrestrial planets would form.

Question 41

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 modified to allow for the formation of gas giants within the frost line.
B)It has been discarded.
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 42

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

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

Question 43

What is an "extrasolar planet"?

A)a planet that is larger than the Sun
B)a planet that is considered an "extra," in that it was not needed for the formation of its solar system
C)a planet that orbits a star that is not our own Sun
D)a planet that is extra large compared to what we'd expect

Question 44

The reason that most extrasolar planets discovered by the Doppler technique are found close to their parent stars is

A)the wavelength shift of the star's spectrum is larger.
B)they transit more frequently, and have thus been more likely to be detected in the short time we have been searching for them.
C)more of the starlight is blocked by the planet when it transits the star.
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 45

The reason that most extrasolar planets discovered by the transit technique are found close to their parent stars is

A)planets that are close to a star are heated up and therefore larger.
B)more of the starlight is blocked by the planet when it transits the star.
C)they transit more frequently, and have thus been more likely to be detected in the short time we have been searching for them.
D)the closer to a star, the hotter and therefore brighter the planet is.
E)the wavelength shift of the star's spectrum is larger.

Question 46

What must be true in order for astronomers to be able to use the Doppler technique to determine a planet's mass?

A)The planet's orbit must be seen nearly face on.
B)The planet must have a very low mass.
C)The planet must have a very eccentric orbit.
D)The planet's orbit must be viewed nearly edge on.

Question 47

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

Question 48

In essence, the Kepler mission searched for extrasolar planets by .

A)obtaining high- resolution photographs of other star systems
B)observing a star carefully enough to notice that it is experiencing a gravitational tug caused by an unseen planet
C)identifying spectral lines that look like what we expect to see from a planet rather than a star
D)monitoring stars for slight dimming that might occur as unseen planets pass in front of them

Question 49

Which of the following statements is not true about the planets so far discovered around other stars?

A)Most of them are more massive than Earth.
B)Photographs reveal that most of them have atmospheres much like that of Jupiter.
C)Many of them orbit closer to their star than Jupiter orbits the Sun.
D)Many of them have been discovered by observing Doppler shifts in the spectra of the stars they orbit.

Question 50

Which of the following methods has led to the most discoveries of extrasolar planet candidates?

A)detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star's spectrum
B)detecting the infrared light emitted by the planet
C)detecting a planet ejected from a binary star system
D)detecting the dip in measured brightness as the planet crosses our line of sight to the star
E)detecting the shift of the star's position against the sky due to the planet's gravitational pull

Question 51

A transiting extrasolar planet is observed to block 1% of its host star's light. How does the size of this planet compare to the host star?

A)The planet's radius is 10% of the host star's radius.
B)The planet's radius is 1% of the host star's radius.
C)The planet's radius is 0.1% of the host star's radius.
D)The planet is the same size as the host star.

Question 52

The planet COROT- 14b is only slightly larger than Jupiter, but is several times more massive. Which is the most plausible explanation for its similar size to Jupiter?

A)The hydrogen and helium gas compressed even under their own gravity to a higher density than Jupiter.
B)It is made of elements other than hydrogen and helium which do not compress under their own gravity.
C)Planets that are close to a star are heated up and therefore larger.
D)The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter.

Question 53

Hot Jupiters were a surprise to astronomers. What is the current explanation for their existence?

A)Jupiters actually can form close to the host star, since they do not require as much hydrogen compounds and ice as originally thought.
B)The temperature of the hot Jupiters is highly uncertain, so they might not be as hot as the astronomers say.
C)Jupiters are supposed to form far away from their host star, and then they migrate closer through gravitational interactions with the protoplanetary disk.
D)Jupiters form as a companion to the host star, but fail to become actual stars themselves because they are not massive enough.

Question 54

How many times must a dip in the brightness of a star be seen in order to detect a planet with the transit technique?

A)1 time
B)2 times
C)3 times
D)4 times

Question 55

The planet HAT- P- 32b has more than twice the radius of Jupiter, yet is only the same mass. It orbits its star more than a factor of ten closer than Mercury's orbit around the Sun. Which is the most plausible explanation for its large size?

A)The hydrogen and helium gas compressed under their own gravity.
B)The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter.
C)It is made of elements other than hydrogen and helium which do not compress under their own gravity.
D)Planets that are close to a star are heated up and therefore larger.

Question 56

You discover that a nearby star, very similar to the Sun, has a velocity curve that has a period of 6 months, induced by the orbit of a planet. You infer that

A)the planet's orbit radius is about 1 AU.
B)the planet's orbit radius is less than 1 AU.
C)the planet's orbit radius cannot be determined based on the information provided.
D)the planet's orbit radius is greater than 1 AU.

Question 57

Measured densities of extrasolar planets range from .

A)water to iron
B)styrofoam to iron
C)styrofoam to water

Question 58

What is the transit method of finding extrasolar planets?

A)measuring the spectrum of the star for a periodic variation in its Doppler shift
B)monitoring a star to detect periodic dips in its brightness from the planet passing behind the star
C)observing a star during the rare occasion of another star passing directly in front of it; slight changes in how the light is bent by gravity can indicate the presence of planets around the closer star
D)monitoring a star to detect periodic dips in its brightness from the planet passing in front of the star

Question 59

A star with planets orbiting in a plane that is not face- on to our line- of- sight exhibit a Doppler effect due to .

A)the planet's mass shifting the path of light from the star
B)the light reflecting from the moving planets
C)the light emitted by the moving planets
D)the planet gravitationally tugging the star

Question 60

Which of the following methods uses the principle of orbital acceleration to detect planets around another star?

A)measuring change in the Doppler shifts of a star over the course of many nights
B)measuring a single Doppler shift of a star, one time
C)measuring the change of light of a star as the planet crosses in front of it
D)taking a picture of the planet next to the star

Question 61

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

Question 62

Describe the impact the discovery of extrasolar planets has had for understanding the origin of our own Solar System.

Question 63

Why is it so difficult to make a direct image of a planet around another star?

Question 64

Briefly describe the three most commonly used methods of indirect planet detection.

Question 65

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

Question 66

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

Question 67

You have observed the wobble in the velocity curves of two otherwise identical stars. Star A has a period of 6 months and Star B has a period of 1 year. What can you say about these stars?

A)Star A's planet is more massive than Star B's planet.
B)It is impossible to say anything about the planets orbiting these stars.
C)Star A's planet must be closer than Star B's planet.
D)Star B must have a planet like Earth.

Question 68

A star is seen to have two transiting planets. Planet 1 transits every 3 months, and Planet 2 transits every 15 months. What can we infer about their orbits?

A)Planet 2's orbit is more eccentric than Planet 1's.
B)Planet 1's semimajor axis is larger than Planet 2's.
C)Planet 1's orbit is more eccentric than Planet 2's.
D)Planet 2's semimajor axis is larger than Planet 1's.

Question 69

The star Rho Cancri B has about the same mass as our Sun, and the planet discovered around it orbits somewhat closer than Mercury orbits our Sun. The mass of the planet is estimated to be 1.1 times the mass of Jupiter. Why, according to our theory of solar system formation, is it surprising to find a planet the size of Rho Cancri B's planet orbiting at this distance?

Question 70

Planetary masses measured using the Doppler technique are lower limits to the possible planetary mass.

Question 71

Indirect detection of an extrasolar planet means .

A)sending a space probe to the planet
B)observing the planet's effect on its host star
C)seeing the planet with the naked eye
D)acquiring images or spectra of the planet

Question 72

Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?

A)Some of the "exceptions to the rules" in our own solar system are likely to have been the result of giant impacts.
B)Planets can migrate from the orbits in which they are born.
C)In addition to the categories of terrestrial and jovian, there must be an "in- between" category of planet that has the mass of a jovian planet but the composition of a terrestrial planet.
D)In some star systems, it is possible for jovian planets to form in the inner solar system and terrestrial planets to form in the outer solar system.

Question 73

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

Question 74

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

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

Question 75

The astrometric technique of planet detection works best for

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

Question 76

The Doppler technique can be used to measure the orbital period of a planet by

A)measuring the speed at which the star orbits the mutual center- of- mass of the star and planet.
B)measuring the amount by which the starlight is reduced when the planet transits.
C)measuring the time it takes for the star's line- of- sight velocity to cycle from peak to peak.
D)measuring the asymmetries in the velocity curve.

Question 77

The majority of planets are estimated to be gas giants.

Question 78

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

Question 79

You are observing the wobble of a star caused by the orbit of a planet around that star. Which property of this system listed below most significantly affects the period of that wobble?

A)the planet's orbital radius
B)the planet's mass
C)both the planet's orbital radius and its mass
D)neither the planet's orbital radius nor its mass

Question 80

Extrasolar planets have been discovered with average densities similar to

A)water.
B)iron.
C)styrofoam.
D)all of the above
E)none of the above