Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
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?
1)
A)
The planet must be closer to the star than Earth is to the Sun.
B)
The planet must have a mass about the same as the mass of Jupiter.
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.
2)
What type of observation can astronomers use to measure the composition of extrasolar planet
atmospheres?
2)
A)
measurement of how frequently the planet blocks the host star’s light
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)
measurements of the host star’s velocity throughout an orbital cycle
3)
What is an “extrasolar planet”?
3)
A)
a planet that is considered an “extra,” in that it was not needed for the formation of its solar
system
B)
a planet that is extra large compared to what we’d expect
C)
a planet that orbits a star that is not our own Sun
D)
a planet that is larger than the Sun
4)
A star with planets orbiting in a plane that is not face–on to our line–of–sight exhibit a Doppler
effect due to ________.
4)
A)
the light emitted by the moving planets
B)
the planet’s mass shifting the path of light from the star
C)
the planet gravitationally tugging the star
D)
the light reflecting from the moving planets
5)
The reason that most extrasolar planets discovered by the Doppler technique are found close to
their parent stars is
5)
A)
they transit more frequently, and have thus been more likely to be detected in the short time
we have been searching for them.
B)
the closer to a star, the hotter and therefore brighter the planet is.
C)
planets that are close to a star are heated up and therefore larger.
D)
the wavelength shift of the star’s spectrum is larger.
E)
more of the starlight is blocked by the planet when it transits the star.
6)
According to the nebular theory, where should jovian planets form?
6)
A)
in the cold outer regions of the disk, where rocks, metals, and ices can condense
B)
within the inner few AU of the disk, where only rocks and metals can condense
C)
at the inner edge of the planet forming disk, where even metal and rock evaporate
7)
At least 70% of stars have planets. How many planets can astronomers reasonably claim exist in the
Milky Way galaxy?
7)
A)
at least 70 billion
B)
at least 8
C)
at least 1 trillion
D)
at least 3000
8)
What mechanism likely accounts for whether a large icy planetesimal becomes a “water world” or a
gas giant?
8)
A)
the presence of other planets to make its orbit highly eccentric
B)
the migration of larger planets through the disk
C)
the timing of when the stellar wind blows away the remaining gas of the planet forming
nebula
D)
the amount of heavy metals initially present in the disk
9)
The first planets around other Sun–like stars were discovered
9)
A)
at the turn of last century.
B)
by Galileo following the invention of the telescope.
C)
at the turn of this century.
D)
about two decades ago.
E)
by Huygens, following his realization that other stars are Suns.
10)
Which of the following is a consequence of the discovery of hot Jupiters for the nebular theory of
solar system formation?
10)
A)
It has been modified to allow for planets to migrate inwards or outwards due to gravitational
interactions.
B)
It has been discarded.
C)
It has been modified to allow for the formation of gas giants within the frost line.
D)
Its status is unclear and awaits further observations that will determine whether hot Jupiters
are dense Earth like planets or gas giants.
11)
Which of the following statements is not true about the planets so far discovered around other
stars?
11)
A)
Photographs reveal that most of them have atmospheres much like that of Jupiter.
B)
Most of them are more massive than Earth.
C)
Many of them have been discovered by observing Doppler shifts in the spectra of the stars
they orbit.
D)
Many of them orbit closer to their star than Jupiter orbits the Sun.
12)
Which new idea has been added into our theory of solar system formation as a result of the
discoveries of extrasolar planets?
12)
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 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.
D)
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.
13)
What extrasolar planet discoveries were initially surprising?
13)
A)
planets with large eccentricities
B)
Jupiter–like planets orbiting very close to their stars
C)
systems with only one planet
D)
A and B
E)
A and C
F)
B and C
14)
Which of the following methods has led to the most confirmed discoveries of massive planets
orbiting near their parent stars?
14)
A)
detecting the infrared light emitted by the planet
B)
detecting a planet ejected from a binary star system
C)
detecting the shift of the star’s position against the sky due to the planet’s gravitational pull
D)
detecting the starlight reflected off the planet
E)
detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the
star’s spectrum
15)
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?
15)
A)
The mass measurement is mistaken, and it is actually about 10 times more massive than
Jupiter.
B)
The hydrogen and helium gas compressed even under their own gravity to a higher density
than Jupiter.
C)
Planets that are close to a star are heated up and therefore larger.
D)
It is made of elements other than hydrogen and helium which do not compress under their
own gravity.
16)
The depth of the dip in a star’s brightness due to the transit of a planet depends most directly on
16)
A)
the eccentricity of the planet’s orbit.
B)
the size of the planet’s orbit.
C)
the planet‘s mass.
D)
the planet’s density.
E)
the planet’s size.
17)
Extrasolar planets have been discovered with average densities similar to
17)
A)
styrofoam.
B)
iron.
C)
water.
D)
all of the above
E)
none of the above
18)
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?
18)
A)
The planet around Star 1 has a thicker atmosphere than the planet around Star 2.
B)
The planet around Star 2 has a thicker atmosphere than the planet around Star 1.
C)
The planet around Star 1 is more massive than the planet around Star 2.
D)
The planet around Star 2 is more massive than the planet around Star 1.
19)
The reason that most extrasolar planets discovered by the transit technique are found close to their
parent stars is
19)
A)
planets that are close to a star are heated up and therefore 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)
the wavelength shift of the star’s spectrum is larger.
D)
the closer to a star, the hotter and therefore brighter the planet is.
E)
more of the starlight is blocked by the planet when it transits the star.
20)
Why are many of the newly detected extrasolar planets called “hot Jupiters”?
20)
A)
The planets tend to be detected around more massive, hotter stars than our Sun.
B)
Their masses and composition are similar to what we would expect if Jupiter were hotter.
C)
Their masses are similar to Jupiter but their composition is similar to Mercury.
D)
Their masses are similar to Jupiter but they are very close to the central star and therefore hot.
E)
because the discovery of other planets is very exciting
21)
How can astronomers measure the period of a planet’s orbit?
21)
A)
by measuring the time between repeated transits
B)
by timing the cycle of small changes in a stars position on the sky
C)
by measuring the time between peaks in the star’s velocity curve
D)
all of the above
22)
How does the theory of planetary migration in disks possibly account for the highly eccentric orbits
discovered for some extrasolar planets?
22)
A)
When migrating planets collide, they would move onto more eccentric orbits.
B)
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.
C)
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.
D)
When a planet migrates onto the surface of the star, the additional stellar mass would disrupt
the orbits of the remaining planets.
23)
What is the transit method of finding extrasolar planets?
23)
A)
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
B)
measuring the spectrum of the star for a periodic variation in its Doppler shift
C)
monitoring a star to detect periodic dips in its brightness from the planet passing in front of
the star
D)
monitoring a star to detect periodic dips in its brightness from the planet passing behind the
star
24)
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)?
24)
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.
25)
What are the two major ways in which extrasolar planets have been discovered?
25)
A)
direct imaging with large telescopes
B)
measuring changes in the star’s brightness when a planet transits
C)
measuring the motion of the star due to the planets’ gravitational tugs
D)
A and B
E)
A and C
F)
B and C
F)
26)
Which of the following methods has led to the most discoveries of extrasolar planet candidates?
26)
A)
detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the
star’s spectrum
B)
detecting the shift of the star’s position against the sky due to the planet’s gravitational pull
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 infrared light emitted by the planet
D
27)
How can astronomers measure the composition of an extrasolar planet’s atmosphere?
27)
A)
by measuring the Doppler shift of the host star
B)
by comparing spectra for when the planet is in transit or eclipse with spectra taken at other
times
C)
by measuring the composition of the host star; the planet must have formed from the same
initial material
D)
by measuring how brightly the planet glows in infrared light
B
F
28)
What is astrometry?
28)
A)
measuring the positions of stars on the sky
B)
measuring distances to stars
C)
searching for planets around stars
D)
measuring the velocities of stars via the Doppler effect
E)
using metric units for distance (e.g., meters rather than light years)
29)
Which two quantities need to be measured in order to determine the density of a planet?
29)
A)
mass
B)
atmospheric composition
C)
radius
D)
A and B
E)
A and C
30)
As of the time of the publication of the textbook, how many planets have been discovered using the
Doppler method?
30)
A)
7
B)
70
C)
7000
D)
700
31)
The Doppler technique can be used to measure the orbital period of a planet by
31)
A)
measuring the time it takes for the star’s line–of–sight velocity to cycle from peak to peak.
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.
32)
Which of the following statements about the accelerations and gravitational forces between a planet
and a star is true?
32)
A)
Forces are equal and opposite; the star is accelerated more than the planet.
B)
Acceleration is equal and opposite; the planet feels more force more than the star.
C)
Acceleration is equal and opposite; the star feels more force more than the planet.
D)
Forces are equal and opposite; the planet is accelerated more than the star.
E)
Accelerations and forces are both equal and opposite.
33)
How many times must a dip in the brightness of a star be seen in order to detect a planet with the
transit technique?
33)
A)
1 time
B)
2 times
C)
3 times
D)
4 times
34)
What could happen in planetary systems where the nebular gas is quickly disbursed?
34)
A)
The only planets would be more massive than Jupiter.
B)
Large ice–rich planetesimals would not be able to gather hydrogen and helium and become
gas giants.
C)
No terrestrial planets would form.
D)
Many planets would be destroyed by migration onto the central star.
35)
Most of the planets discovered around other stars using the Doppler technique
35)
A)
are less massive than Earth and orbit very close to the star.
B)
are found around neutron stars.
C)
are more massive than Earth and orbit very far from the star.
D)
are less massive than Earth and orbit very far from the star.
E)
are more massive than Earth and orbit very close to the star.
36)
Direct detection of an extrasolar planet means ________.
36)
A)
sending a space probe to the planet
B)
acquiring images or spectra of the planet
C)
observing the planet’s effect on its host star
D)
seeing the planet with the naked eye
37)
Indirect detection of an extrasolar planet means ________.
37)
A)
seeing the planet with the naked eye
B)
acquiring images or spectra of the planet
C)
observing the planet’s effect on its host star
D)
sending a space probe to the planet
38)
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 signicantly affects the period of that wobble?
38)
A)
the planet’s mass
B)
the planet’s orbital radius
C)
both the planet’s orbital radius and its mass
D)
neither the planet’s orbital radius nor its mass
39)
According to Kepler results in mid–2013, what fraction of stars host an Earth–size planet?
39)
A)
about 70%
B)
about 15%
C)
about 20%
D)
about 100%
40)
Hot Jupiters were a surprise to astronomers. What is the current explanation for their existence?
40)
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.
41)
Approximately how many other planetary systems have been discovered to date?
41)
A)
tens of thousands
B)
about two thousand
C)
millions
D)
ten
E)
about two hundred
42)
At least ________ % of stars host at least one planet.
42)
A)
30
B)
10
C)
70
D)
1
43)
What must be true in order for astronomers to be able to use the Doppler technique to determine a
planet’s mass?
43)
A)
The planet’s orbit must be viewed nearly edge on.
B)
The planet’s orbit must be seen nearly face on.
C)
The planet must have a very low mass.
D)
The planet must have a very eccentric orbit.
44)
What are the two main differences between extrasolar planetary systems discovered to date and
our Solar System?
44)
A)
Extrasolar planet orbits tend to be closer and more eccentric than in our Solar System.
B)
Extrasolar planets tend to be bigger and denser than Jupiter.
C)
Extrasolar planet orbits tend to be more eccentric and inclined 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 more massive and dense than Jupiter.
45)
Which planet search technique is currently best suited to finding Earth–like planets?
45)
A)
transit
B)
gravitational lensing
C)
Doppler
D)
astrometric
E)
combining all the above
A
46)
The Doppler technique can be used to estimate the semimajor axis of a planet’s orbit by
46)
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.
A
47)
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?
47)
A)
Star B must have a planet like Earth.
B)
Star A’s planet must be closer than Star B’s planet.
C)
It is impossible to say anything about the planets orbiting these stars.
D)
Star A’s planet is more massive than Star B’s planet.
B
A
48)
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.
48)
A)
Planet A is farther from Star A than Planet B is to Star B.
B)
Planet A is closer to Star A than Planet B is to Star B.
C)
Planet A is more massive than Planet B.
D)
Planet A is less massive than Planet B.
E)
Not possible to say, since you’re measuring the velocity curve of the stars, not the planets.
49)
Measured densities of extrasolar planets range from ________.
49)
A)
water to iron
B)
styrofoam to iron
C)
styrofoam to water
50)
How can astronomers currently determine the temperature of an extrasolar planet?
50)
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
51)
The Doppler technique can be used to measure the eccentricity of a planet’s orbit by
51)
A)
measuring the amount by which the starlight is reduced when the planet transits.
B)
measuring the asymmetries in the velocity curve.
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 speed at which the star orbits the mutual center–of–mass of the star and
planet, and using Newton’s theory of gravity.
52)
What mechanism explains the presence of “hot Jupiters” around many other stars?
52)
A)
evaporation of the disk by the stellar wind removes gas that was holding the planet at a large
radius
B)
gravitational attraction by terrestrial planets that formed at small radii attract the giant
planets inward
C)
planetary migration caused by gravitational interactions between the planet and disk
D)
rapid formation of the gas giant from evaporated rock and metal at the inner disk edge
53)
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?
53)
A)
It is made of elements other than hydrogen and helium which do not compress under their
own gravity.
B)
Planets that are close to a star are heated up and therefore larger.
C)
The hydrogen and helium gas compressed under their own gravity.
D)
The mass measurement is mistaken, and it is actually about 10 times more massive than
Jupiter.
B
54)
The astrometric technique of planet detection works best for
54)
A)
massive planets around nearby stars.
B)
large planets around distant stars.
C)
large planets around nearby stars.
D)
massive planets around distant stars.
E)
planets in edge–on orbits.
A
55)
What is a so–called “hot Jupiter”?
55)
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
B
C
56)
In essence, the Kepler mission searched for extrasolar planets by ________.
56)
A)
identifying spectral lines that look like what we expect to see from a planet rather than a star
B)
monitoring stars for slight dimming that might occur as unseen planets pass in front of them
C)
observing a star carefully enough to notice that it is experiencing a gravitational tug caused
by an unseen planet
D)
obtaining high–resolution photographs of other star systems
57)
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
57)
A)
the planet’s orbit radius is greater than 1 AU.
B)
the planet‘s orbit radius is less than 1 AU.
C)
the planet’s orbit radius is about 1 AU.
D)
the planet’s orbit radius cannot be determined based on the information provided.
58)
How do we think the “hot Jupiters” around other stars were formed?
58)
A)
They formed as gas giants 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 dense, rocky planets close to the star in the same orbits that they are seen
today.
59)
All of the following hypothetical planets orbit a star with the same mass as the Sun (one solar
mass). Which one has the shortest orbital period? (If two objects would have the same orbital
period to within a difference of less than 1% consider them as having identical periods.)
59)
A)
Planet A: one Earth mass and 1 AU from the star
B)
Planet B: two Earth masses and 1 AU from the star
C)
Planet C: two Earth masses and 2 AU from the star
D)
Planets A and B
E)
Planets B and C
F)
All of them have the same period.
Explanation:
60)
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)
60)
A)
Planet 2’s semimajor axis is about 3 times smaller than Planet 1‘s.
B)
Planet 2’s semimajor axis is about 5 times smaller than Planet 1‘s.
C)
Planet 2’s semimajor axis is about 3 times larger than Planet 1’s.
D)
Planet 2’s semimajor axis is about 5 times larger than Planet 1’s.
61)
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
61)
A)
II and III
B)
I and III
C)
I and II
62)
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 ________.
62)
A)
0.0005 arcsecond
B)
0.5 arcsecond
C)
0.005 arcsecond
D)
0.05 arcsecond
63)
Which of the following methods uses the principle of orbital acceleration to detect planets around
another star?
63)
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)
taking a picture of the planet next to the star
D)
measuring the change of light of a star as the planet crosses in front of it
64)
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?
64)
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.
65)
What is the chief difficulty in attempting to detect planets around other stars?
65)
A)
Planets do not emit visible light. They are typically at least a billion times fainter than their
host stars.
B)
Even the largest planets are typically at least a factor of 10 times smaller 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
D
66)
The transit method of planet detection works best for
66)
A)
Earth–like planets in any orbit.
B)
big planets in edge–on orbits around small stars.
C)
big planets in face–on orbits around small stars.
D)
small planets in face–on orbits around big stars.
E)
small planets in edge–on orbits around big stars.
B
67)
Planets detected via the Doppler technique have been mostly
67)
A)
a wide range of masses, in edge–on orbits.
B)
Jupiter–mass, in Jupiter–like orbits.
C)
Earth–mass, in Earth–like orbits.
D)
Jupiter–mass, in very close orbits.
E)
Earth–mass, in very close orbits.
D
D
68)
What would happen to the planets in a solar system where the central star did not have a strong
wind?
68)
A)
The gas in the solar nebula would create a drag on the planets and their orbits would migrate
inwards.
B)
Nothing, the star does not affect the process of planet formation.
C)
One planet would grow to dominate all the others and gravitationally eject them out of the
system.
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.
69)
As of the time of the publication of the textbook, how many planet candidates have been
discovered using the transit method?
69)
A)
tens of thousands
B)
about 10
C)
a few thousand
D)
a few hundred
70)
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?
70)
A)
planets between 4 Earth radii and 10 Earth radii in size
B)
planets between 1 Earth radius and 4 Earth radii in size
C)
planets greater than 10 Earth radii in size
D)
planets less than 1 Earth radius in size
71)
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?
71)
A)
The planet‘s radius is 0.1% of the host star’s radius.
B)
The planet is the same size as the host star.
C)
The planet’s radius is 10% of the host star’s radius.
D)
The planet’s radius is 1% of the host star’s radius.
72)
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?
72)
A)
The relative orbital speeds depend on the masses of the planets.
B)
Planet A moves with the same speed as Planet B.
C)
Planet A is, on average, moving faster than Planet B.
D)
Planet A is, on average, moving slower than Planet B.
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
73)
Briefly describe the three most commonly used methods of indirect planet detection.
73)
74)
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?
74)
75)
Why is it so difficult to make a direct image of a planet around another star?
75)
76)
Describe the impact the discovery of extrasolar planets has had for understanding the
origin of our own Solar System.
76)
TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false.
77)
Planetary masses measured using the Doppler technique are lower limits to the possible planetary
mass.
77)
78)
In the searches so far, only about 1 in 10 stars show evidence for planets around them.
78)
79)
Most of the planets discovered around other stars have masses comparable to the terrestrial planets
in our own solar system.
79)
80)
The majority of planets are estimated to be gas giants.
80)
81)
A planet’s size can be determined by observing its transit across a star.
81)
82)
A planet’s density can be determined if it is observed to periodically transit in front of its parent
star causing eclipses.
82)
83)
Once a planet forms in a disk–like nebula around a star, its orbit is fixed and will never change.
83)
84)
Astronomers have discovered more extrasolar planets around other stars than the number of
planets in our own Solar System.
84)
85)
The Doppler technique for planet detection has found Earth–like planets around nearby Sun–like
stars
85)
86)
Only Earth–size terrestrial planets and Jupiter–size gas giants have been discovered in other
planetary systems.
86)
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
87)
Discoveries force theory revisions: The discovery of “hot Jupiters” forced scientists to revise the nebular theory of
solar system formation. Think of a hypothetical discovery that would force further revisions of the theory of
planet formation, and explain why this observation would contradict the theory.
88)
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?
89)
Kepler’s Impact: In four years of operation, the Kepler satellite discovered nearly three times as many extrasolar
planet candidates as had been discovered in the previous 15 years (since the first discovery of an extrasolar
planet). Discuss how these observations changed our understanding of the population of planets and of planet
formation.
Answer Key
Testname: C10
Answer Key
Testname: C10
Answer Key
Testname: C10
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