Chapter 10
Which two quantities need to be measured in order to determine the density of a planet? A) mass B) atmospheric composition C) radius D) AandB E) A and C
E
Approximately how many other planetary systems have been discovered to date? A) ten B) tens of thousands C) about two thousand D) millions E) about two hundred
C
What is astrometry? A) using metric units for distance (e.g., meters rather than light years) B) measuring the velocities of stars via the Doppler effect C) searching for planets around stars D) measuring the positions of stars on the sky E) measuring distances to stars
D
Which planet search technique is currently best suited to finding Earth-like planets? A) astrometric B) Doppler C) gravitational lensing D) transit E) combining all the above
D
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.
A
At least ________ % of stars host at least one planet. A) 70 B) 1 C) 10 D) 30
A
Most of the planets discovered around other stars using the Doppler technique A) are more massive than Earth and orbit very close to the star. B) are less massive than Earth and orbit very close to the star. C) are found around neutron stars. D) are more massive than Earth and orbit very far from the star. E) are less massive than Earth and orbit very far from the star.
A
The Doppler technique can be used to estimate the semimajor axis 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 speed at which the star orbits the mutual center-of-mass of the star and planet, and using Newton's theory of gravity. D) measuring the asymmetries in the velocity curve.
A
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) planets that are close to a star are heated up and therefore 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.
A
What are the two main differences between extrasolar planetary systems discovered to date and our Solar System? A) Extrasolar planet orbits tend to be closer and more eccentric than in our Solar System. B) Extrasolar planet orbits tend to be closer and more circular than in our Solar System. C) Extrasolar planet orbits tend to be more eccentric and inclined than in our Solar System. D) Extrasolar planets tend to be more massive and dense than Jupiter. E) Extrasolar planets tend to be bigger and denser than Jupiter.
A
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 easing the drop in brightness of the host star when the planet crosses our line of sight. A) II andIII B) I and II C) I and III
A
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 asymmetries in the velocity curve. C) 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. D) measuring the amount by which the starlight is reduced when the planet transits.
B
The depth of the dip in a star's brightness due to the transit of a planet depends most directly on A) the eccentricity of the planet's orbit. B) the planet's size. C) the planet's mass. D) the planet's density. E) the size of the planet's orbit.
B
The first planets around other Sun-like stars were discovered A) At the turn of last century. B) About two decades ago. C)By Huygens, following his realization that other stars are Sun. D) By Galileo following the invention of the telescope. E) At the turn of this century
B
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) Planets that are close to a star are heated up and therefore larger. C) The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter. D) It is made of elements other than hydrogen and helium which do not compress under their own gravity.
B
The transit method of planet detection works best for A) Earth-like planets in any orbit. B) big planets in edge-on orbits around small stars. C) small planets in edge-on orbits around big stars. D) big planets in face-on orbits around small stars. E) small planets in face-on orbits around big stars.
B
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
B
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) The gas in the solar nebula would create a drag on the planets and their orbits would migrate inwards. C) All planets would continue to grow to large sizes but their orbits would be unchanged. D) One planet would grow to dominate all the others and gravitationally eject them out of the system. E) The gas in the solar nebula would create a drag on the planets and their orbits would migrate outwards.
B
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) Their masses are similar to Jupiter but they are very close to the central star and therefore hot. C) The planets tend to be detected around more massive, hotter stars than our Sun. D) Their masses are similar to Jupiter but their composition is similar to Mercury. E) because the discovery of other planets is very exciting
B
How does the theory of planetary migration in disks possibly account for the highly eccentric orbits discovered for some extrasolar planets? A) 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. B) When a planet migrates onto the surface of the star, the additional stellar mass would disrupt the orbits of the remaining planets. 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 migrating planets collide, they would move onto more eccentric orbits.
C
Planets detected via the Doppler technique have been mostly A) Earth-mass, in Earth-like orbits. B) a wide range of masses, in edge-on orbits. C) Jupiter-mass, in very close orbits. D) Jupiter-mass, in Jupiter-like orbits. E) Earth-mass, in very close orbits.
C
The astrometric technique of planet detection works best for A) large planets around nearby stars. B) massive planets around distant stars. C) massive planets around nearby stars. D) large planets around distant stars. E) planets in edge-on orbits.
C
Extrasolar planets have been discovered with average densities similar to A) iron. B) styrofoam. C) water. D) all of the above E) none of the above
D
How can astronomers currently determine the temperature of an extrasolar planet? A) measure the drop in total infrared light when the planet passes behind the star from our perspective B) estimate the temperature based on the planet's distance from the star C) use spectroscopy of the planet to identify the wavelength at which its emission peaks D) AandB E) B and C
D
The Doppler technique can be used to measure the orbital period of a planet by 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 speed at which the star orbits the mutual center-of-mass of the star and planet. D) measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak.
D
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) 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 mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter. D) The hydrogen and helium gas compressed even under their own gravity to a higher density than Jupiter.
D
The reason that most extrasolar planets discovered by the transit technique are found close to their parent stars is A) the closer to a star, the hotter and therefore brighter the planet is. B) more of the starlight is blocked by the planet when it transits the star. C) the wavelength shift of the star's spectrum is larger. D) they transit more frequently, and have thus been more likely to be detected in the short time we have been searching for them. E) planets that are close to a star are heated up and therefore larger.
D
What could happen in planetary systems where the nebular gas is quickly disbursed? A) No terrestrial planets would form. B) The only planets would be more massive than Jupiter. C) Many planets would be destroyed by migration onto the central star. D) Large ice-rich planetesimals would not be able to gather hydrogen and helium and become gas giants.
D
What is the chief difficulty in attempting to detect planets around other stars? A) Planets do not emit visible light. They are typical at least a billion times faint than their host stars. B) Even the largest planets are typically at least 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
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) Its status is unclear and awaits further observations that will determine whether hot Jupiters are dense Earth like planets or gas giants. D) It has been modified to allow for planets to migrate inwards or outwards due to gravitational interactions.
D
Which of the following methods has led to the most discoveries of extrasolar planet candidates? A) detecting a planet ejected from a binary star system B) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star's spectrum C) detecting the infrared light emitted by the planet 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
D
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 starlight reflected off the planet D) detecting the infrared light emitted by the planet E) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star's spectrum
E
