Astronomy Midterm 2.10

Which two quantities need to be measured in order to determine the density of an extrasolar planet? a) mass and radius b) orbital period and mass c) radius and composition d) mass and composition e) radius and orbital period

a) mass and radius

Statistical evidence suggests that about ________ percent of all stars have an approximately Earth-sized planet orbiting in a region around the star where water could exist as a liquid on the planet's surface. a) 10 b) 20 c) 30 d) 40

b) 20

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

a) Planets that are close to a star are puffed up and therefore larger.

What is the most accurate way to measure the surface temperature of an extrasolar planet? a) measure the drop in total infrared light when the planet passes behind the star b) identify the planet's peak wavelength of emission c) identify the composition of the planet's atmosphere through spectroscopy d) estimate the temperature based on the planet's mass e) calculate the size of the planet by the amount of light it blocks during transit

a) measure the drop in total infrared light when the planet passes behind the star

The reason that most extrasolar planets discovered by the Doppler method are found close to their parent stars is a) the wavelength shift of the star's spectrum is larger. 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) they transit more frequently, and have thus been more likely to be detected in the short time we have been searching for them. e) more of the starlight is blocked by the planet when it transits the star.

a) the wavelength shift of the star's spectrum is larger.

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 are similar to Jupiter but they are very close to the central star and therefore hot. c) Their masses and composition are similar to what we would expect if Jupiter were hotter. 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

b) Their masses are similar to Jupiter but they are very close to the central star and therefore hot.

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 greater than 10 Earth radii in size b) planets between 1 Earth radius and 4 Earth radii in size c) planets less than 1 Earth radius in size d) planets between 4 Earth radii and 10 Earth radii in size

b) planets between 1 Earth radius and 4 Earth radii in size

The depth of the dip in a star's brightness due to the transit of a planet depends most directly on a) the size of the planet's orbit. b) the planet's size. c) the planet's mass. d) the planet's density. e) the eccentricity of the planet's orbit.

b) the planet's size.

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 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.

c) The planet's radius is 10% of the host star's radius.

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 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 a planet ejected from a binary star system e) detecting the starlight reflected off the planet

c) detecting the gravitational effect of an orbiting planet by looking for the Doppler shifts in the star's spectrum

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) all of the above

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

d) detecting the dip in measured brightness as the planet crosses our line of sight to the star

The Doppler method can be used to estimate the semimajor axis of a planet's orbit by a) measuring the asymmetries in the velocity curve. 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 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 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.