Deck 5: Exoplanets

Question 1

What is the microlensing technique?

A) A small telescope is placed in orbit around Earth to observe extrasolar planets.
B) A planet that passes between Earth and some distant star focuses the starlight and causes an increase in its apparent brightness.
C) Refracting telescopes for use in the search for extrasolar planets are constructed with very small lenses to avoid the problems of large refraction telescopes.
D) A planet passing between Earth and its star focuses the light from the star and makes it appear to brighten.

Answer 1

A planet that passes between Earth and some distant star focuses the starlight and causes an increase in its apparent brightness.

Question 2

In the search for planets around other stars,which possible line of evidence has NOT yet been seen?

A) a warped disk of dust and gas around a young star
B) the wavy path of a star through space, as if the star were being tugged by an orbiting planet
C) faint pinpoints of light slowly circling a star
D) cyclic Doppler shift variations in a star's spectrum

Answer 2

faint pinpoints of light slowly circling a star

Question 3

In 2004,an object designated 2M1207b was directly imaged orbiting the brown dwarf 2M1207.The object,however,has not been designated a planet because it:

A) does not have enough gravity to form a spherical shape.
B) does not clear its orbit of debris.
C) does not orbit a star.
D) is smaller than Mercury.

Answer 3

does not orbit a star.

Question 4

What type of search technique has discovered the second largest number of exoplanets?

A) distorted protoplanetary disks
B) the transit method
C) the radial-velocity method
D) the astrometric method

Question 5

What was the FIRST direct evidence that some other solar-type stars might have planets?

A) faint pinpoints of light slowly circling some stars, as seen through the new 8- and 10-meter telescopes
B) slightly wavy path of a star through space, as if the star were being tugged by an orbiting planet
C) cyclic Doppler shift variations in the spectra of several stars
D) warped disks of dust and gas around some young stars

Question 6

What type of search technique has discovered the second largest number of planets around stars other than the Sun?

A) looking for tiny variations in the star's position in the sky, caused by the gravitational pull of one or more planets orbiting the star
B) looking for tiny variations in the star's radial velocity, caused by the gravitational pull of one or more planets orbiting the star
C) looking for excess infrared radiation from the star, caused by the presence of planets that are cool and thus emitting primarily in the infrared
D) using space-based telescopes to search for tiny pinpoints of light that follow circular or elliptical paths around the star

Question 7

Comets been discovered around the star Beta Pictoris.How was this belt discovered?

A) The comets were imaged directly by the Hubble Space Telescope when they are close to the star and glowing brightly.
B) Comets travel far from the star, enough so that they can be imaged outside its glare.
C) The comets emit gas when they pass close to the star.
D) The gravitational effects of the comets cause the star to wobble slightly in its proper motion.

Question 8

Strong evidence for the existence of planetary systems in the process of formation around other stars comes from:

A) detection of very regular pulses of radio energy from some stars.
B) spectroscopic evidence of large quantities of molecules such as ammonia and methane, which can exist only in planetary atmospheres.
C) direct photography of actual planets near other stars.
D) periodic wobbling of the positions and spectral line displacements of several nearby stars.

Question 9

Disks of gas and dust have been found around:

A) the Sun only.
B) young stars only.
C) Red giants only.
D) stars of various ages.

Question 10

In studying newly forming star regions such as the Great Nebula of Orion,which portion of the electromagnetic spectrum is MOST valuable?

A) infrared
B) visible
C) gamma ray
D) X-ray

Question 11

In searches for planets orbiting stars other than the Sun,what is the astrometric method?

A) searching for tiny "bumps" on images of a star, due to the light from a planet located close to the star
B) searching for tiny displacements of the infrared image of a star compared with its optical image, caused by the presence of planets that are cool and thus emitting primarily in the infrared
C) searching for tiny wobbles in the position of a star, due to the gravitational pull of a planet orbiting around it
D) searching for tiny wobbles in the positions of absorption lines in a star's spectrum, caused by radial-velocity variations of the star as the result of a planet orbiting around it

Question 12

What type of search technique has discovered the largest number of exoplanets?

A) distorted protoplanetary disks
B) the transit method
C) the radial-velocity method
D) the astrometric method

Question 13

Exoplanets were first observed in:

A) 1810.
B) 1931.
C) 1992.
D) 2012.

Question 14

Observers in a distant solar system are watching our Sun and using the radial-velocity method to try to determine whether the Sun has planets.Because of the gravitational pull of Jupiter,the observers see the Sun's spectrum slowly redshift and then blueshift by a tiny amount.How long must they observe to see a full cycle?

A) 25 days
B) 1 year
C) almost 12 years
D) It depends on how far away the observers are.

Question 15

During the 1860s,a hypothetical planet named Vulcan,in a solar orbit closer to the Sun than Mercury,was proposed as the cause of abnormalities in Mercury's orbit.Much of the 1860s and 1870s was spent studying the solar disk waiting for Vulcan to cross.Vulcan never appeared (but we learned a great deal about sunspots!).This technique is like which exoplanet-discovery technique?

A) distorted protoplanetary disks
B) the transit method
C) the radial-velocity method
D) the astrometric method

Question 16

It is believed that the stellar disk around the star Beta Pictoris contains a Jupiter-size planet.What is the reason behind this belief?

A) The planet was imaged directly by the Hubble Space Telescope.
B) Effects of the intense magnetic field of this planet can be detected by powerful radio telescopes.
C) The gravitational effect of this planet has created an off-center disk of dust and gas around the star.
D) The planet causes a measurable decrease in the brightness of Beta Pictoris when it transits across its disk.

Question 17

What type of search technique has discovered the largest number of planets around the stars other than the Sun?

A) looking for tiny variations in the star's position in the sky, caused by the gravitational pull of one or more planets orbiting the star
B) looking for small variations in the light of a distant star indicating motion of a planet across the face of the star
C) looking for excess infrared radiation from the star, caused by the presence of planets that are cool and thus emitting primarily in the infrared
D) using space-based telescopes to search for tiny pinpoints of light that follow circular or elliptical paths around the star

Question 18

Extrasolar planets have NOT been found:

A) around burned-out remnants of stars.
B) around stars in the disks of other galaxies.
C) in globular clusters.
D) around stars in the disk of our Galaxy.

Question 19

An asteroid belt has been discovered around the star Zeta Leporis.How were these comets discovered?

A) The asteroids were imaged directly by the Hubble Space Telescope.
B) A ring of hot dust was discovered around the star by spectroscopy, and collisions among asteroids were inferred as the cause.
C) The gravitational effects of the asteroids have created an off-center disk of dust and gas around the star.
D) The gravitational effects of the asteroids cause the star to wobble slightly in its proper motion.

Question 20

The oldest extrasolar planets have been found in:

A) open clusters.
B) black holes.
C) globular clusters.
D) the nucleus of our Galaxy.

Question 21

Many of the exoplanets discovered thus far are in orbits near their stars.This means they are probably:

A) spinning rapidly to conserve angular momentum.
B) doomed to spiral into their stars.
C) recently formed.
D) in synchronous orbits.

Question 22

A particular star shows spectral lines of the lithium isotope ⁶Li.What conclusion do astronomers draw from this observation?

A) The star has vaporized one of its planets that spiraled in too close to the star because the star's own ⁶Li was destroyed by nuclear reactions long ago.
B) The star has not yet begun nuclear reactions in its core because these reactions destroy ⁶Li.
C) Planets must be orbiting around the star because only planets show ⁶Li spectral lines.
D) The star is composed of pristine (unmodified) material from the Big Bang because ⁶Li has been destroyed in material that has been processed in stars and expelled back into space.

Question 23

What type of search technique has discovered the largest number of systems with multiple exoplanets?

A) distorted protoplanetary disks
B) the transit method
C) the radial-velocity method
D) the astrometric method

Question 24

The atmosphere of the gas-giant planet HD 209458b is believed to contain hydrogen,sodium,oxygen,carbon,and carbon monoxide.Where does this information come from?

A) All known gas giants contain these molecules, so it is assumed that this one does also.
B) Light shines through the planet's atmosphere when it passes in front of its star, so a spectrum can be taken.
C) As the planet orbits its star, it leaves a trail of atmosphere behind. This can be analyzed spectroscopically.
D) Gas giants always have the same composition as their stars, and we have measured the spectrum of HD 209458.

Question 25

The age of the oldest extrasolar planet is estimated to be about:

A) half a million years.
B) 4.5 billion years, similar to Earth's age.
C) only a few thousand years.
D) 13 billion years.

Question 26

The exoplanet HAT P-32b,discovered in 2011 in the constellation Andromeda,has been measured to have a mass about the same as Jupiter's but a radius about twice that of Jupiter.How does its density compare with Jupiter's density?

A) It is smaller than Jupiter's density.
B) It is about the same as Jupiter's density.
C) It is twice Jupiter's density.
D) It is eight times Jupiter's density.

Question 27

What is the typical mass of the majority of extrasolar planets so far discovered?

A) roughly the mass of Jupiter up to a few times Jupiter's mass
B) a few times the mass of Earth
C) quite large-between 10 and 100 times Jupiter's mass
D) very small-between one-tenth and a few tenths of the mass of Earth

Question 28

MOST extrasolar planets have been found:

A) around stars in the disk of our Galaxy.
B) in globular clusters.
C) near the center of our Galaxy.
D) outside our Galaxy.

Question 29

In what way are many of the extrasolar planetary systems that have been discovered so far fundamentally different from our own solar system?

A) The relative positions of where the planets formed are inverted, with the Jovian-type planets forming close to the stars and the terrestrial-type planets forming farther out.
B) The terrestrial-mass planets are significantly outnumbered by the Jovian-mass planets.
C) The massive Jovian-type planets appear to have formed at large distances, like our own Jovian planets, and then spiraled in close to their stars.
D) There are no Jovian-mass planets.

Question 30

Approximately how many planets are believed to exist in our Galaxy?

A) eight
B) a few thousand
C) around a million
D) at least 100 billion

Question 31

What is surprising about the extrasolar planets that have so far been discovered?

A) More than half of the extrasolar planets have strong lines of molecular oxygen in their spectra, a possible indication of life on these planets.
B) The majority of the extrasolar planets rotate much faster than the planets in our solar system.
C) Many of the extrasolar planets are giant planets like Jupiter, orbiting at distances characteristic of terrestrial planets like Earth, where giant planets cannot form.
D) Many of the extrasolar planets are terrestrial planets like Earth, orbiting at distances characteristic of giant planets like Jupiter, where terrestrial planets cannot form.

Question 32

Of the perhaps 200 billion stars estimated to exist in the Galaxy,about how many are believed to be have Earth-like planets orbiting them close to the star?

A) almost none
B) a few million
C) perhaps 35 billion
D) almost all of them

Question 33

We have begun to observe exoplanets not orbiting stars.How do we think they were formed?

A) They were formed around stars that died, cooled, and are no longer visible.
B) They were formed in dust clouds, as are stars, but in this case the star did not form.
C) They formed from free-floating planetesimals that had escaped from various solar systems.
D) They formed normally in solar systems but then were forced out by the gravitational influences of other masses.

Question 34

The largest exoplanet discovered thus far has a radius about how many times Earth's radius?

A) 2
B) 10
C) 25
D) 800

Question 35

We have discovered planets in each of the following situations EXCEPT ONE.Which is the exception?

A) around Sunlike stars
B) in globular clusters
C) orbiting black holes
D) not in orbit around a star (free-floating)

Question 36

How do we measure the mass of an extrasolar planet?

A) We use Newton's law of gravity, using the measured distance of the planet from its star and the planet's gravitational pull on the star.
B) We measure the change in the brightness of a distant star that the planet causes by microlensing.
C) We use spectra to measure the planet's temperature and photometry to measure its brightness.
D) We measure the planet's angular diameter and hence its size and then use spectra to find its composition and hence density.

Question 37

The habitable zone in our own solar system encompasses:

A) all of the terrestrial planets.
B) Venus, Earth, and Mars only.
C) Earth and Mars only.
D) Earth only.

Question 38

In order for an exoplanet to be capable of sustaining life,all of the following situations would have to be true EXCEPT ONE.Which is the exception?

A) The planet would have to be far enough from its star that liquid water would not boil away.
B) The planet would have to be close enough to its star that liquid water would not be permanently frozen.
C) The planet would have to revolve around a Sun-like star.
D) The planet would have to be in a solar system containing a giant planet in a highly eccentric orbit.

Question 39

Calculations suggest that the number of free-floating planets in the Milky Way Galaxy is:

A) only a relative few since they must occur very rarely.
B) a few thousand at most.
C) around a billion.
D) more numerous than the stars.

Question 40

At the present time,the discoveries of how many extrasolar planets have been confirmed?

A) none
B) one
C) a few thousand
D) millions

Question 41

All of the following characteristics are usually taken to be sufficient to rule out the existence of life on an extrasolar planet EXCEPT ONE.Which is the exception?

A) The planet is too close to the star.
B) It is a large, gas planet with no solid surface.
C) The planet has a highly eccentric orbit.
D) The star around which the planet orbits is older than the Sun.

Question 42

What is the status of our search for life elsewhere in the universe?

A) Life has been discovered elsewhere in the solar system.
B) Signs of life have been discovered on Earth-like planets circling other stars elsewhere in the Milky Way Galaxy.
C) Earthlike planets, with an abundance of liquid water, have been discovered around other stars, but signs of life have not yet been found on them.
D) No exoplanets in habitable zones have yet been discovered.

Question 43

Which characteristic in extrasolar planets is one for which we look as a likely characteristic of a life-bearing planet?

A) large size (Jupiter-sized)
B) an oxygen-rich atmosphere
C) an orbit around a star much more massive than the Sun
D) a highly eccentric planetary orbit