Deck 5: Exoplanets and the Formation of Planetary Systems

Question 1

The solar system was formed about how long after the Big Bang?

A) immediately
B) a few hundred million years
C) 9 billion years
D) 13.8 billion years

Answer 1

9 billion years

Question 2

The MOST likely mechanism for the formation of a star and planetary system is that the

A) star and planets slowly condensed to their present form from a gas and dust cloud.
B) star captured the planets as they drifted through space.
C) system was once a galaxy from which the star and planets are the remnants, after evolution.
D) planets were spun out of the star as smaller gas clouds and subsequently condensed.

Answer 2

star and planets slowly condensed to their present form from a gas and dust cloud.

Question 3

The majority of the elements beyond hydrogen and helium in the periodic table in the Sun and the solar system most likely originated in

A) the center of our own Sun, through fusion and later ejection as solar wind.
B) chemical reactions in planetary atmospheres.
C) the original Big Bang of the universe.
D) fusion reactions in the centers of earlier stars.

Answer 3

fusion reactions in the centers of earlier stars.

Question 4

What fraction of the mass of the universe is in the form of atoms other than hydrogen and helium?

A) 10%
B) much less than 1%
C) 2%
D) 50%

Question 5

The MOST common elements in the universe are

A) about equal amounts of all elements up to iron but very little of any heavier elements.
B) hydrogen and helium, with small amounts of heavier elements.
C) nitrogen and oxygen, with smaller quantities of hydrogen, helium, and heavier elements.
D) heavy elements, with smaller quantities of hydrogen and helium.

Question 6

What fraction of the mass of Earth is made up of the elements hydrogen and helium?

A) about 70%
B) 2%
C) much less than 1%
D) 98%

Question 7

What was the material from which the solar system formed?

A) nebula made mostly of heavy elements but enriched in hydrogen and helium from supernova explosions
B) debris from the explosion of a massive star
C) nebula made entirely of hydrogen and helium gas
D) nebula made mostly of hydrogen and helium gas but enriched in heavier elements from planetary nebulae and supernova explosions

Question 8

The majority of our body weight comes from heavy elements such as carbon and oxygen, which asserts the fact that

A) our bodies have converted the original hydrogen and helium into heavier elements.
B) the Big Bang model of the universe must be wrong.
C) the solar system did not form directly from the material created by the Big Bang.
D) the Big Bang created elements unevenly because the Sun, unlike our bodies, is mostly hydrogen and helium.

Question 9

Most of the mass of the universe-98%-is in the form of

A) hydrogen and helium.
B) nitrogen and oxygen.
C) iron and silicon.
D) hydrogen.

Question 10

The outer layers of stars expel material into space by a variety of mechanisms. Which of these is NOT one of the mechanisms?

A) stellar winds
B) planetary nebula
C) supernovae
D) fusion

Question 11

The MOST abundant material in the universe is

A) nitrogen.
B) carbon dioxide.
C) water.
D) hydrogen.

Question 12

Hydrogen and helium together account for what percentage of the total mass of all the matter in the universe?

A) 90%
B) 98%
C) 75%
D) about 50%

Question 13

What is a planetary nebula?

A) nebula of gas and dust around a giant planet
B) nebula of gas and dust around any planet
C) clouds of matter ejected into space by a dying star
D) result of a stellar explosion in which the entire star is blown apart

Question 14

Where in the universe are heavy elements with masses greater than that of helium being produced at this time?

A) in the central cores of stars
B) in the surface layers of stars
C) at the event horizons of massive black holes
D) in the dark clouds of dust and gas

Question 15

What is thought to be the physical mechanism that was responsible for the present mix of chemical elements in the universe?

A) All the known elements have been formed by the breakup (radioactivity) of the heavy elements formed in the initial Big Bang.
B) All the known elements were formed in the Big Bang.
C) Hydrogen and helium were formed in the Big Bang, whereas the heavier elements have been slowly forming by collisions in cold interstellar gas clouds.
D) Hydrogen and helium were formed in the Big Bang, whereas the heavier elements were made in the centers of stars.

Question 16

The universe contains about 10 times as many hydrogen atoms as helium atoms, but a helium atom has 4 times the mass of a hydrogen atom. What is the approximate ratio of the universe's hydrogen to helium by mass?

A) 2.5 to 1
B) 10 to 1
C) 4 to 1
D) 1 to 4

Question 17

All of these are possible mechanisms believed to be capable of triggering the collapse of a cloud of gas and dust to form stars EXCEPT

A) stellar winds may compress nearby gas and dust clouds.
B) a nearby supernova can compress nearby gas and dust clouds.
C) clouds can collide and compress each other.
D) radiation pressure from the cosmic microwave background can compress clouds of gas and dust.

Question 18

How was the vast majority of the hydrogen in the universe formed?

A) in nuclear reactions in the cores of stars
B) in supernovae (exploding stars)
C) in the dark clouds of dust and gas
D) in the Big Bang, at the very beginning of the universe

Question 19

The composition of matter in the universe can be summarized by which statement?

A) All but 2% of the mass of the universe is hydrogen and helium.
B) All but 2% of the mass of the universe is hydrogen.
C) Two percent of the mass of the universe is hydrogen and helium. The rest is of heavier elements.
D) About half of the mass of the universe is in the form of rocks, molecules, and planetary material.

Question 20

The birthplace of a star and planetary system is thought to have been in

A) cool gas and dust clouds.
B) the centers of supernova explosions.
C) black holes dotted about the universe.
D) the centers of galaxies.

Question 21

The presence of dusty disks surrounding stars similar to the Sun was surprising because

A) such systems could not have formed planets.
B) their composition differs so much from their stars.
C) their instruments were not thought to be powerful enough to make such a measurement.
D) gas and dust should be rapidly ejected into space by the radiation from a hot star.

Question 22

Comets have been discovered around the star Beta Pictoris through

A) emission from gas evaporated when the comets pass close to their star.
B) impacts on the system's gas giants.
C) their gravitational effects on the system's small planets.
D) obscuration caused by dust evaporated from the comets' nuclei.

Question 23

What is the Jeans instability?

A) When a growing protoplanet becomes too large, it is more likely to be split apart by subsequent bombardment than to grow further.
B) If a solar nebula is too massive it will continue to collapse to become a black hole and will not form planets.
C) If the disk of matter surrounding a solar nebula becomes too hot, it will dissipate, and planets will not form.
D) If a cloud of gas and dust is sufficiently dense, it will collapse due to its own gravity.

Question 24

The observation of hot dust around nearby stars implies that those stars have

A) asteroids.
B) a solar wind.
C) much higher luminosity than the Sun.
D) Kuiper belts.

Question 25

The Kepler Space Telescope discovered thousands of exoplanets by measuring

A) reflected light from the planets.
B) periodic variability in the brightness of stars.
C) periodic variability in the positions of stars on the sky.
D) periodic variability in the radial velocities of stars.

Question 26

A gas and dust cloud will not necessarily collapse because it normally experiences a balance between its internal gas pressure and

A) kinetic energy.
B) friction.
C) gravity.
D) electrostatic repulsion.

Question 27

Which characteristic MOST directly determines whether a piece of material inside a dense core will eventually become part of the protostar or the protoplanetary disk that surrounds it?

A) composition
B) kinetic energy
C) temperature
D) rotational speed

Question 28

Which of these have been detected around nearby stars?

A) Comets
B) Asteroids
C) terrestrial planets
D) All of these are correct.

Question 29

Suppose a dense core forms out of an interstellar cloud that is unusual because it does NOT rotate. How might the resulting protostar differ from the majority of other protostars?

A) It would begin fusion at a higher internal temperature.
B) It would most likely lack a protoplanetary disk.
C) It would take much longer to form.
D) It would use a different set of fusion reactions to power itself.

Question 30

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 31

A gas and dust cloud that is unstable and will collapse is characterized by all of these EXCEPT

A) low temperature.
B) rapid internal motion.
C) low pressure.
D) high density.

Question 32

MOST protostars are surrounded by

A) gas giants.
B) brown dwarfs.
C) disks of dust without gas.
D) disks of gas and dust.

Question 33

In astronomy, a dense core is a region in the process of forming a

A) star.
B) black hole.
C) white dwarf.
D) galactic bulge.

Question 34

Young stars are sometimes observed to have multiple debris disks inclined relative to each other. This phenomenon is a result of

A) winds from the young star.
B) variability from an active young star.
C) the gravitational influence of massive planets in the system.
D) collisions between asteroids.

Question 35

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

A) spectroscopic evidence of large quantities of molecules such as ammonia and methane, which can exist only in planetary atmospheres.
B) images and infrared observations of disks of dust.
C) detection of very regular pulses of radio energy from some stars.
D) direct photography of actual planets near other stars.

Question 36

An asteroid belt has been discovered around the star Zeta Leporis. How was this belt 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 37

An astronomer discovers a protoplanetary disk with spiral waves. This may be evidence for

A) planetary nebulae.
B) jets from the young star.
C) planets in the disk.
D) comets.

Question 38

Asteroids have been detected around nearby stars through

A) ripples observed in the protoplanetary disks around these stars.
B) hot dust generated by collisions amongst the asteroids.
C) reflected light from the star.
D) spectral lines from gas evaporated from the asteroids.

Question 39

An astronomer is trying to detect an exoplanet via the transit method. Which of these changes to a particular planet will make it EASIER to detect, if everything else about the planet is unchanged?

A) increasing its radius
B) increasing its mass
C) increasing its orbital period
D) All of these are correct.

Question 40

Astronomers have searched for extrasolar planets for decades. Which one of these statements about the current status of the search is NOT true?

A) No evidence of planets beyond our own solar system has been found.
B) Astronomers have seen disks of material around stars that resemble the solar nebula believed to be an early stage in the formation of our solar system.
C) Astronomers have seen asteroid belts around other stars.
D) Astronomers actually have images of other stars being orbited by planets.

Question 41

Which of these provides a plausible method to measure the mass of an exoplanet?

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 cannot make any firm estimate of the mass of an extrasolar planet with present technology.
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 42

For an exoplanet to be detected via the astrometric method, it must

A) orbit its star with a component of its motion parallel to the line of sight to from the star to Earth.
B) orbit its star with a component of its motion perpendicular to the line of sight to from the star to Earth.
C) have a low albedo.
D) have a high albedo.

Question 43

An astronomer is trying to detect an exoplanet via the radial velocity method. Which of these changes to a particular planet will make it harder to detect, if everything else about the planet is unchanged?

A) decreasing its orbital period
B) decreasing its mass
C) decreasing its radius
D) decreasing its albedo

Question 44

An astronomer is trying to detect an exoplanet via the phase cycle brightness method. Which of these changes to a particular planet will make it easier to detect, if everything else about the planet is unchanged?

A) decreasing its mass
B) increasing its mass
C) decreasing its albedo
D) increasing its albedo

Question 45

The transit photometry method for detecting extrasolar planets around distant stars relies on variations in the star's

A) brightness.
B) velocity.
C) position on the sky.
D) spectrum.

Question 46

In order to detect multiple planets around a single star using the transit photometry method, the planets must have nearly the same

A) orbital periods.
B) masses.
C) orbital plane.
D) diameters.

Question 47

For an exoplanet to be detected via the direct imaging method, it must

A) have a large mass.
B) orbit its star with a component of its motion perpendicular to the line of sight to from the star to Earth.
C) be the only exoplanet in the system.
D) have a high albedo.

Question 48

Exoplanets have been detected around binary stars through

A) their effects on the spectra of the stars.
B) the slow increase in the orbital period of the stars, induced by the planet's gravity.
C) the slow decrease in the orbital period of the stars, induced by the planet's gravity.
D) their effects on the timing of eclipses of the stars.

Question 49

Which of these methods for detecting exoplanets requires astronomers to take spectra of the stars around which the exoplanets orbit?

A) astrometric method
B) radial velocity method
C) transit photometry method
D) transit timing method

Question 50

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 emit 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 51

Astronomers believe that the stellar disk around the star Beta Pictoris contains a Jupiter-size planet. Why do they think this?

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 52

An exoplanet discovered through the transit photometry method is unlikely to also be detectable with what other method of detecting exoplanets?

A) astrometric method
B) radial velocity method
C) variable transit timing method
D) phase cycle brightness method

Question 53

What type of search technique has discovered the 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 tiny variations in the star's brightness, caused by the planet moving in front of the star
D) using space-based telescopes to search for tiny pinpoints of light that follow circular or elliptical paths around the star

Question 54

An astronomer is trying to detect an exoplanet via the radial velocity method. Which of these changes to a particular planet will make it easier to detect, if everything else about the planet is unchanged?

A) increasing its radius
B) increasing its mass
C) increasing its orbital period
D) All of these are correct.

Question 55

Which of these pairs of exoplanet detection methods are MOST similar in the physical processes underlying the methods?

A) The transit duration time variation and eclipsing binary minima variation methods
B) The astrometric and transit photometry methods
C) The phase cycle brightness and radial velocity methods
D) The distorted disk and radial velocity methods

Question 56

Which of these solar system events is MOST analogous to the phase cycle brightness method for detecting exoplanets?

A) the lunar cycle
B) solar eclipses
C) the gravitational motion of the Sun induced by the planets
D) lunar eclipses

Question 57

Some moons of exoplanets have been detected through

A) their effects on the measured radial velocities of exoplanets.
B) their effects on the duration of exoplanet transits.
C) their infrared emission.
D) the light they reflect from their star.

Question 58

An astronomer is trying to detect an exoplanet via the astrometric method. Which of these changes to a particular planet will make it easier to detect, if everything else about the planet is unchanged?

A) increasing its radius
B) increasing its mass
C) increasing its orbital period
D) All of these are correct.

Question 59

After studying an exoplanet system carefully, astronomers determine that the intervals between the transits of a given exoplanet vary in a complex fashion. This most likely indicates that the system

A) has an exoplanet with a thick atmosphere.
B) is actually a binary star.
C) has multiple exoplanets.
D) has an exoplanet with a ring system.

Question 60

Which of these methods has provided strong evidence for the existence of hundreds of planetary systems around other stars?

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 61

Observations of the exoplanet HD 209458 b have revealed that it is rapidly losing the outermost layers of its atmosphere. Why?

A) the gravitational attraction of its star
B) the gravitational attraction of a nearby planet
C) collisions with small bodies
D) heating from its star

Question 62

The oldest extrasolar planets have been found in

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

Question 63

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) Many terrestrial planets discovered so far have masses intermediate between the terrestrial planets of our system and the ice giants.
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 64

The majority of 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 65

Which method of detecting exoplanets has revealed the MOST about the detailed structure and composition of exoplanets?

A) radial velocity method
B) transit method
C) direct imaging
D) microlensing

Question 66

Which of these features have NOT been detected to date around exoplanets?

A) circumplanetary disks
B) oxygen-rich atmospheres
C) moons
D) rings

Question 67

Planets have been discovered in each of these situations EXCEPT

A) around Sunlike stars.
B) in globular clusters.
C) orbiting black holes.
D) around binary star systems.

Question 68

The very first exoplanets to be discovered were found through

A) distorted protoplanetary disks.
B) variations in the stars radial velocity.
C) pulsar timing.
D) transits of the exoplanet in front of its star.

Question 69

How have astronomers studied the atmospheres of exoplanets?

A) by timing the duration of consecutive transits
B) by resolving images of exoplanets and searching for color variations
C) by measuring absorption of starlight during transits
D) by measuring emission lines of directly imaged planets

Question 70

How do the exoplanets discovered through pulsar timing differ from nearly all the other exoplanets discovered to date?

A) They are more massive.
B) They are older.
C) They have larger diameters.
D) They are closer to Earth.

Question 71

Which of these characteristics of the extrasolar planets that have so far been discovered surprised astronomers?

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 were not believed to be able to form.
D) Many of the extrasolar planets are terrestrial planets like Earth, orbiting at distances characteristic of giant planets like Jupiter, where terrestrial planets were not believed to be able to form.

Question 72

Why did the discovery of a 17 Earth mass terrestrial exoplanet surprise astronomers?

A) It implies that Earth lost a great deal of mass in the early solar system.
B) Such a large planetary mass was thought to be gravitationally unstable.
C) Models had predicted that the formation of such a large rocky core requires a protoplanetary disk many times larger than that of the solar system.
D) Models had predicted that a rocky protoplanet of such a mass would attract enough hydrogen to form a gas giant.

Question 73

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

A) none
B) hundreds
C) thousands
D) millions

Question 74

How far away is the nearest known exoplanet?

A) 0.42 light-year
B) 4.2 light-years
C) 42 light-years
D) 42,000 light-years

Question 75

Which of these methods for detecting exoplanets is MOST analogous to the pulsar timing method?

A) transit method
B) microlensing
C) distorted protoplanetary disk
D) radial velocity method

Question 76

What kind of orbits can exoplanets in binary star systems have?

A) Astronomers do not know, because none have been detected so far.
B) They orbit only one of the stars.
C) They have an orbit around the center of mass of both stars.
D) Some orbit one of the stars, while some have an orbit around the center of mass of both stars.

Question 77

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

A) roughly the size of Earth
B) 1.5-3 times the size of Earth
C) roughly the size of Jupiter
D) larger than Jupiter

Question 78

To date, all the exoplanets detected through the direct imaging method are

A) larger than Jupiter.
B) super-Earths.
C) hot Jupiters.
D) ice giants.

Question 79

An astronomer is trying to detect an exoplanet via the microlensing method. Which of these changes to a particular planet will make it easier to detect, if everything else about the planet is unchanged?

A) increasing its radius
B) increasing its mass
C) increasing its orbital period
D) All of these are correct.

Question 80

An exoplanet detected through microlensing causes

A) variations in the brightness of a star that is distant from both the exoplanet and Earth.
B) variations in the brightness of the star the exoplanet orbits.
C) variations in the spectrum of a star that is distant from both the exoplanet and Earth.
D) variations in the spectrum of a star that the exoplanet orbits.