Deck 13: Other Planetary Systems: The New Science of Distant Worlds

Question 1

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

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

Answer 1

C

Question 2

The transit method of planet detection works best for

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

Answer 2

A

Question 3

Current techniques can measure stellar motion to less than

A)walking speed.
B)running speed.
C)freeway speed.
D)cruising speed of an airplane.
E)orbital speed of Jupiter.

Answer 3

A

Question 4

The size and shape of a planet's orbit can be determined by

A)the Doppler technique.
B)transit observations.
C)spectral measurements.
D)knowing the planet's mass by any technique and applying Newton's version of Kepler's third law.
E)gravitational microlensing.

Question 5

What is astrometry?

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

Question 6

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

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

Question 7

Which planet can we see occasionally transit across the face of the Sun?

A)Mercury
B)Mars
C)Jupiter
D)Uranus
E)all of the above

Question 8

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

A)tens
B)hundreds
C)thousands
D)tens of thousands
E)millions

Question 9

By itself,the Doppler technique provides a measure of a planet's

A)minimum mass.
B)orbital radius.
C)orbital eccentricity.
D)all of the above

Question 10

Most of the planets discovered around other stars

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

Question 11

The composition of a planet can be determined by

A)the Doppler technique.
B)astrometric measurements.
C)transit observations.
D)spectra.
E)all of the above

Question 12

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

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

Question 13

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 last century.
D)about a decade ago.
E)at the turn of this century.

Question 14

How much brighter is a Sun-like star than the reflected light from a planet orbiting around it?

A)a hundred times brighter
B)a thousand times brighter
C)ten thousand times brighter
D)a million times brighter
E)a billion times brighter

Question 15

Planets detected via the Doppler technique have been mostly

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

Question 16

A planet's density can be measured by combining

A)Doppler and astrometric observations.
B)Doppler and transit observations.
C)spectral observations of the planet's atmosphere.
D)any method that measures the gravitational tug of the planet on the star.
E)direct imaging from the new generation of space telescopes.

Question 17

The reason that most extrasolar planets are found close to their parent stars is

A)the planets reflect more light the closer they are to the star.
B)more of the starlight is blocked by the planet when it transits the star.
C)the amount and frequency of the star's motion are both higher.
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 18

The Doppler technique only provides a measure of the minimum mass of a planet because

A)only a small part of the planet's motion is measured.
B)without a transit observation,the size and therefore density of the planet is unknown.
C)we do not know the exact composition of the planet.
D)only the motion of star toward the observer is measured,not the full motion.
E)we do not have the technology to make a direct image of a planet yet.

Question 19

The astrometric technique of planet detection works best for

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

Question 20

A planet is detected via the Doppler technique.The velocity change of the star is a measure of

A)the planet's size and density.
B)the planet's mass and orbital distance.
C)the planet's mass and composition.
D)the planet's orbital period and eccentricity.
E)the planet's size and orbital distance.

Question 21

Planetary orbits that are face-on to our line of sight produce no Doppler shift in the stellar spectrum.

Question 22

The Kepler mission has been able to measure dimmings of less than 0.01% in a star's brightness.This has allowed us to detect what size planets?

A)planets smaller than Earth
B)planets Earth-size only
C)only planets larger than Earth
D)any size planet,as long as they are in binary star systems

Question 23

If every star had an Earth-like planet in an Earth-like orbit,how many could be detected by a transit?

A)1 in 2
B)1 in 20
C)1 in 200
D)1 in 2,000
E)1 in 20,000

Question 24

Most of the planets discovered around other stars are more massive than Jupiter.

Question 25

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

Question 26

Astronomers have discovered more planets around other stars than in our Solar System.

Question 27

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

Question 28

A planet is detected via the Doppler technique.The repeating pattern of the stellar motion tells us

A)the planet's size.
B)the planet's mass.
C)the planet's density.
D)the orbital period of the planet.
E)the orbital eccentricity of the planet.

Question 29

A planet is detected via the Doppler technique.The shape of the periodic velocity pattern tells us

A)the planet's size.
B)the planet's mass.
C)the planet's density.
D)the orbital period of the planet.
E)the orbital eccentricity of the planet.

Question 30

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

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

Question 31

Which of the following is a consequence of the discovery of hot Jupiters for understanding our own Solar System?

A)It shows that our Solar System is very unusual.
B)It shows that our Solar System is very typical.
C)It shows that we do not fully understand the formation of our Solar System.
D)It shows that life in the Universe is rare.
E)It shows that Jupiter is unusually cold.

Question 32

What do models suggest make up the clouds on "hot Jupiters"?

A)ammonia
B)methane
C)water
D)rock dust
E)sodium

Question 33

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 discarded.
B)It has been modified to allow for the formation of gas giants within the frost line.
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.
E)It remains unchanged as it only needs to explain our Solar System.

Question 34

The composition of a planet's atmosphere be measured during a transit by analyzing

A)the excess absorption of starlight at specific wavelengths.
B)the excess emission of starlight at specific wavelengths.
C)the length and depth of the dip in light during the transit.
D)the amplitude and period of the star's motion.
E)the wobble in a star's position on the sky.

Question 35

The density of a planet can be determined by combining Doppler and astrometric measurements.

Question 36

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

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

Question 37

The GAIA mission obtains astrometric data of stars with accuracy in some cases better than 10 microarcseconds.In terms of angular width,what is this equal to?

A)A human hair viewed from a distance of 20 miles
B)A human hair viewed from a distance of 200 miles
C)A human hair viewed from a distance of 2000 miles
D)A human hair viewed from a distance of 20000 miles

Question 38

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

Question 39

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

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

Question 40

Viewed from afar,the transit of Earth would cause the Sun's brightness to dim by approximately one part in

A)100.
B)1,000.
C)10,000.
D)100,000.
E)a million.

Question 41

Because we have not found another planetary system like our own,we can conclude that our Solar System must be quite unusual.

Question 42

The signature of a planet is largest in radial velocity measurements when the planet and star are lined up along the line of sight to the telescope.

Question 43

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

Question 44

Calculate how much (as a percentage)an Earth transit would reduce the light from the Sun as viewed from a distant planetary system.

Question 45

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 46

Transits of multiple planet systems can be analyzed to infer planetary masses.

Question 47

Amateur astronomers are able to detect extrasolar planets with backyard telescopes using the transit method.

Question 48

Describe one of the future planned space missions to search for extrasolar planets.How will it improve on current observations?

Question 49

What do astronomers mean by a "selection effect".Explain why the detection of giant planets in close orbits does not necessarily mean our Solar System is unusual.

Question 50

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

Question 51

The star 55 Cancri has a triple planetary system.From exoplanets.org,we find that the orbital period of the of the third,outermost planet (55 Cancri d)is 5360 days = 14.7 years.It produces a velocity offset in the star of 49.3 m/s.The star itself is spectral type G8V with mass 0.95 MSᵤn.Calculate the orbital distance and mass of 55 Cancri d.

Question 52

Describe the impact the discovery of extrasolar planets h as had on the question of life on other worlds.

Question 53

The signature of a planet is largest in transit measurements when the planet and star are lined up along the line of sight to the telescope.

Question 54

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

Question 55

Drag within the solar nebula is responsible for hot Jupiters.

Question 56

HD 209458b was the first extrasolar planet whose size was measured.It has a radius of 1.43 Jupiter radii and mass of 0.63 Jupiter masses.Calculate its average density in grams per cubic centimeter.How does this compare with Jupiter?

Question 57

Multiple-planet systems have been identified around other stars via the Doppler technique.

Question 58

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

Question 59

Multiple planets have been identified around other stars via the transit technique.

Question 60

The total amount of light from a star-planet system drops when the planet goes behind the star.

Question 61

How will the Kepler mission (scheduled for 2008 launch)look for planets around other stars?

A)It will look for Doppler shifts in stellar spectra.
B)It will be sufficiently powerful to take low-resolution photographs of planets orbiting nearby stars.
C)It will look for slight back and forth shifts in a star's position in our sky.
D)It will look for slight changes in a star's brightness that repeat at regular intervals.

Question 62

In essence,most of the extrasolar planets discovered to date have been found by

A)closely examining very 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)observing mini-eclipses of a star as an unseen planet passes in front of it.

Question 63

Process of Science: Why did some astronomers think that we would not be able to detect planetary systems around other stars so quickly as we did?

Question 64

Why do we say that the Doppler technique gives the planet's "minimum mass"?

A)The size of the Doppler shift that we detect depends on whether the planet's orbit is tilted.
B)The size of the Doppler shift that we detect depends on knowing the star's mass,which can be very uncertain.
C)Extrasolar planets are always increasing in mass.
D)Doppler measurements are very difficult,producing noisy data that often cause astronomers to underestimate a planet's mass.

Question 65

How are the orbits of extrasolar planets different from the orbits of planets in our solar system?

A)Many extrasolar planets orbit their stars backward.
B)Many extrasolar planets are on very tilted orbits compared to what we'd expect.
C)Many extrasolar planets do not travel on elliptical orbits.
D)Many extrasolar planets travel on very eccentric orbits.

Question 66

Why is our Jupiter not a "hot Jupiter"?

Question 67

About how many extrasolar planets have been discovered (as of 2008)?

A)tens
B)hundreds
C)thousands
D)tens of thousands

Question 68

As of 2008,most known extrasolar planets have been discovered by

A)the astrometric technique.
B)the Doppler technique.
C)the transit technique.
D)the Hubble Space Telescope.

Question 69

Process of Science: Name a testable hypothesis from nebular theory that was proven true in observations of extrasolar planets.Does this mean the theory is complete?

Question 70

Based on available data,what kind of objects in our solar system do most of the known extrasolar planets resemble?

A)jovian planets
B)terrestrial planets
C)Kuiper belt objects
D)None of the above: most extrasolar planets apparently belong to some new category of object.

Question 71

Why do other systems have planetary types that don't fall neatly into the terrestrial and jovian categories that we identify in our solar system?

Question 72

Process of Science:
Name a testable hypothesis of nebular theory that was shown to be false in observations of extrasolar planets.Must we throw out the theory and start from scratch,i.e. ,is the observation completely inconsistent with a nebular formation?

Question 73

How do we expect that the first Earth-sized extrasolar planets will be discovered (if they exist)?

A)by the transit technique from an observatory in space
B)with photographs from a new generation of large,ground-based observatories
C)by NASA's Terrestrial Planet Finder mission
D)by the Doppler technique

Question 74

What is an extrasolar planet?

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

Question 75

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

A)Most of them are much 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 76

What information does the Doppler technique give about an extrasolar planet?

A)the planet's radius
B)the planet's density
C)the planet's minimum mass
D)all of the above

Question 77

What is the closest that extrasolar planets have been found to their stars?

A)nearer to their stars than Earth to the Sun
B)nearer to their stars than Saturn to the Sun
C)nearer to their stars than Mercury to our Sun
D)unknown: we do not know the distance with enough accuracy to say

Question 78

Which detection techniques can find the planet's orbital distance (assuming we know the mass of the star)?

A)only the Doppler technique
B)only the transit technique
C)only the astrometric technique
D)all of these techniques

Question 79

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

A)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.
B)Jovian 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)Some of the "exceptions to the rules" in our own solar system are likely to have been the result of giant impacts.

Question 80

Why is it so difficult to take pictures of extrasolar planets?

A)Extrasolar planets give off light at different wavelengths than planets in our solar system.
B)No telescope is powerful enough to detect the faint light from a distant planet.
C)Their light is overwhelmed by the light from their star.
D)Telescopes are too busy with other projects.