Astronomy by Fraknoi, Morrison, and Wolff
Multiple Choice Questions for Chapter 21:
The Birth of Stars and the Discovery of Planets Outside the Solar System
by Andrew Fraknoi
Section 21.1: Star Formation
1. If you want to find stars that are just being born, where are the best places to search?
a. in HII regions
b. in giant molecular clouds
c. in regions of ultra-hot interstellar hydrogen gas
d. in the disks around massive stars that were just recently formed
e. Hollywood
2. Which of the following are the small regions that are the embryos of stars (where
individual stars are most likely to be born)?
a. local bubbles
b. the cores within the clumps of molecular clouds
c. HII regions
d. spiral galaxies
e. the parts of the interstellar medium where the temperature is millions of degrees
3. The Orion Nebula is
a. a distant galaxy of stars and raw material
b. a small disk of gas and dust surrounding a single star that was recently formed
c. a large cloud of gas and dust illuminated by the light of newly formed stars within it
d. the remnant of a star that exploded several thousand years ago
e. an illusion caused by activity in the Earth's upper atmosphere
4. If an astronomer wants to find and identify as many stars as possible in a star cluster
that has recently formed near the surface of a giant molecular cloud (such as the
Trapezium cluster in the Orion Nebula), what instrument would be best for her to use?
a. an infra-red telescope (and camera)
b. an x-ray telescope
c. a very good camera attached to a large reflector telescope on the ground
d. an ultraviolet spectrograph attached to the Hubble Space Telescope
e. the instruments that were part of the Compton Gamma Ray Observatory
5. You are an astronomy graduate student and you are observing the big Orion Nebula
from an airplane that has a good-sized infrared telescope built into it (there really is such a
plane.) On an infrared image of the Nebula, what would particularly stand out?
,a. the stars that are visible in our sky as the constellation of Orion
b. HII regions (ionized hydrogen regions) in the Nebula
c. the clouds of the nebula that have a lot of dust in them
d. hot Jupiters close to their stars
e. none of the above
6. Astronomers studying regions like the Orion Giant Molecular Cloud have observed that a
wave of star formation can move through them over many millions of years. What
sustains such a wave of star formation in a giant molecular cloud?
a. radio waves from complex molecules move slowly through the cloud, causing stars to
form
b. when a group of stars form, they remove so much material from the cloud that only a
big empty place is left, into which new matter from other clouds falls, making more stars
c. when massive stars form, their ultraviolet radiation and later their final explosions
compress the gas in the cloud and cause a new group of stars to form
d. when giant molecular clouds collide with each other, they do so not just once, but
many times
e. the dust in these clouds is so heavy, it is always settling inward toward the cloud's
center causing star formation in its wake
7. Why is it so difficult for astronomers to see new stars in the process of birth?
a. birth happens very quickly, so it is hard to "catch" stars "in the act"
b. most stars are born inside dusty clouds, which block any light that may be coming from
the stars
c. the size of a newly forming star is typically quite small and thus hard to make out
d. protostars which are not yet doing fusion do not give off a lot of visible light
e. all of the above
8. Astronomers call a ball of matter that is contracting to become a star
a. a Herbig-Haro object
b. a giant molecular cloud
c. a planet
d. a protostar
e. a main sequence star
9. A Herbig-Haro (HH) object is
a. a small galaxy just outside the outer edge of the Milky Way
b. where a jet from a star in the process of being born collides with (and lights up) a
nearby cloud of interstellar matter
c. a part of a giant molecular cloud where molecules containing two hydrogen atoms form
d. a star that has too little mass to start fusion in its core
e. cluster of very low-mass stars, observable only with infrared radiation
,10. Astronomers believe that disks of material will form around protostars that are
spinning. Which of the following observed phenomena is a good indication of the
presence of a disk around a protostar?
a. HII regions
b. huge pillars of dust, like those seen by the Hubble in the Eagle Nebula
c. jets and Herbig-Haro objects
d. the presence of molecules in giant clouds of gas and dust
e. gamma rays detected from the direction of giant molecular clouds
Section 21.2: The H-R Diagram and the Study of Stellar Evolution
11. A star whose temperature is increasing but whose luminosity is roughly constant
moves in what direction on the H-R diagram?
a. to the right
b. to the left
c. upwards
d. downwards
e. you can't fool me; stars don't move on the H-R diagram
12. In figuring out the evolutionary tracks on the H-R diagram, astronomers
a. look at fossils from many times in Earth’s history in a museum
b. observe one star over the course of several decades
c. make model stars on a computer and then follow how their characteristics will change
with time
d. use big telescopes to observe how the outer layers of stars fall in during the protostar
stage
e. send robot probes to the Sun
13. Astronomers identify the "birth" of a real star (as opposed to the activities of a
protostar) with what activity in the star?
a. when it starts to contract rapidly from a cloud of gas and dust
b. when it first becomes visible inside its dust cloud
c. when a wind is observed coming from its surface
d. when nuclear fusion reactions begin inside its core
e. when it glows with infrared radiation
14. When a star settles down to a stable existence as a main-sequence star, what
characteristics determines where on the main sequence in an H-R diagram the star will
fall?
a. its mass
b. the fraction of its atmosphere that consists of hydrogen
c. whether it is located on the outer regions or the central regions of the molecular cloud
that gave it birth
d. the speed and direction of its rotation
, e. the size of the disk around it
15. Which of these stars will take the SHORTEST time to go from the earliest protostar
stage to the main sequence?
a. a star 1/10th the mass of our Sun
b. a star ½ the mass of our Sun
c. a star equal to the mass of our Sun
d. a star ten times the mass of our Sun
e. all of these stars take the same time to get to the main sequence
Section 21.3: Evidence that Planets Form Around Other Stars
16. Which of the following is NOT one of the reasons planets around other stars are so
difficult to detect?
a. planets don't give off their own light, but only reflect the light of their stars
b. planets are small compared to stars, and so don't have much surface area from which
to reflect light
c. from far away, planets are typically lost in the glare of their parent star
d. planets have much less mass than stars
e. planets only form very late in the life of a star, just when it is ready to die, and thus last
only a very short fraction of the star's life
17. A graduate student is given the assignment to find stars with dusty disks around
them. What kind of telescope would it be best for her to use for this purpose?
a. a small telescope that detects visible light
b. a large telescope that detects infrared radiation
c. any telescope that can detect x-rays
d. an orbiting telescope that can detect ultra-violet rays
e. the students should worry; any telescope can easily show such dusty disks
18. What observations about disks of dusty material around young stars suggest that
planets may be forming in such disks?
a. the disks give off x-rays and gamma-rays characteristic of small planets
b. the disks show lanes that are empty of dust within them
c. the disks show evidence of very strong winds coming from the star
d. the disks are making the stars "wiggle" -- move back and forth across the sky -- in a
way that can be observed even with small telescopes
e. radio telescopes have revealed transmissions from the disks that include rap songs and
other evidence of advanced civilizations
Section 21.4: Planets Beyond the Solar System: Search and Discovery
Multiple Choice Questions for Chapter 21:
The Birth of Stars and the Discovery of Planets Outside the Solar System
by Andrew Fraknoi
Section 21.1: Star Formation
1. If you want to find stars that are just being born, where are the best places to search?
a. in HII regions
b. in giant molecular clouds
c. in regions of ultra-hot interstellar hydrogen gas
d. in the disks around massive stars that were just recently formed
e. Hollywood
2. Which of the following are the small regions that are the embryos of stars (where
individual stars are most likely to be born)?
a. local bubbles
b. the cores within the clumps of molecular clouds
c. HII regions
d. spiral galaxies
e. the parts of the interstellar medium where the temperature is millions of degrees
3. The Orion Nebula is
a. a distant galaxy of stars and raw material
b. a small disk of gas and dust surrounding a single star that was recently formed
c. a large cloud of gas and dust illuminated by the light of newly formed stars within it
d. the remnant of a star that exploded several thousand years ago
e. an illusion caused by activity in the Earth's upper atmosphere
4. If an astronomer wants to find and identify as many stars as possible in a star cluster
that has recently formed near the surface of a giant molecular cloud (such as the
Trapezium cluster in the Orion Nebula), what instrument would be best for her to use?
a. an infra-red telescope (and camera)
b. an x-ray telescope
c. a very good camera attached to a large reflector telescope on the ground
d. an ultraviolet spectrograph attached to the Hubble Space Telescope
e. the instruments that were part of the Compton Gamma Ray Observatory
5. You are an astronomy graduate student and you are observing the big Orion Nebula
from an airplane that has a good-sized infrared telescope built into it (there really is such a
plane.) On an infrared image of the Nebula, what would particularly stand out?
,a. the stars that are visible in our sky as the constellation of Orion
b. HII regions (ionized hydrogen regions) in the Nebula
c. the clouds of the nebula that have a lot of dust in them
d. hot Jupiters close to their stars
e. none of the above
6. Astronomers studying regions like the Orion Giant Molecular Cloud have observed that a
wave of star formation can move through them over many millions of years. What
sustains such a wave of star formation in a giant molecular cloud?
a. radio waves from complex molecules move slowly through the cloud, causing stars to
form
b. when a group of stars form, they remove so much material from the cloud that only a
big empty place is left, into which new matter from other clouds falls, making more stars
c. when massive stars form, their ultraviolet radiation and later their final explosions
compress the gas in the cloud and cause a new group of stars to form
d. when giant molecular clouds collide with each other, they do so not just once, but
many times
e. the dust in these clouds is so heavy, it is always settling inward toward the cloud's
center causing star formation in its wake
7. Why is it so difficult for astronomers to see new stars in the process of birth?
a. birth happens very quickly, so it is hard to "catch" stars "in the act"
b. most stars are born inside dusty clouds, which block any light that may be coming from
the stars
c. the size of a newly forming star is typically quite small and thus hard to make out
d. protostars which are not yet doing fusion do not give off a lot of visible light
e. all of the above
8. Astronomers call a ball of matter that is contracting to become a star
a. a Herbig-Haro object
b. a giant molecular cloud
c. a planet
d. a protostar
e. a main sequence star
9. A Herbig-Haro (HH) object is
a. a small galaxy just outside the outer edge of the Milky Way
b. where a jet from a star in the process of being born collides with (and lights up) a
nearby cloud of interstellar matter
c. a part of a giant molecular cloud where molecules containing two hydrogen atoms form
d. a star that has too little mass to start fusion in its core
e. cluster of very low-mass stars, observable only with infrared radiation
,10. Astronomers believe that disks of material will form around protostars that are
spinning. Which of the following observed phenomena is a good indication of the
presence of a disk around a protostar?
a. HII regions
b. huge pillars of dust, like those seen by the Hubble in the Eagle Nebula
c. jets and Herbig-Haro objects
d. the presence of molecules in giant clouds of gas and dust
e. gamma rays detected from the direction of giant molecular clouds
Section 21.2: The H-R Diagram and the Study of Stellar Evolution
11. A star whose temperature is increasing but whose luminosity is roughly constant
moves in what direction on the H-R diagram?
a. to the right
b. to the left
c. upwards
d. downwards
e. you can't fool me; stars don't move on the H-R diagram
12. In figuring out the evolutionary tracks on the H-R diagram, astronomers
a. look at fossils from many times in Earth’s history in a museum
b. observe one star over the course of several decades
c. make model stars on a computer and then follow how their characteristics will change
with time
d. use big telescopes to observe how the outer layers of stars fall in during the protostar
stage
e. send robot probes to the Sun
13. Astronomers identify the "birth" of a real star (as opposed to the activities of a
protostar) with what activity in the star?
a. when it starts to contract rapidly from a cloud of gas and dust
b. when it first becomes visible inside its dust cloud
c. when a wind is observed coming from its surface
d. when nuclear fusion reactions begin inside its core
e. when it glows with infrared radiation
14. When a star settles down to a stable existence as a main-sequence star, what
characteristics determines where on the main sequence in an H-R diagram the star will
fall?
a. its mass
b. the fraction of its atmosphere that consists of hydrogen
c. whether it is located on the outer regions or the central regions of the molecular cloud
that gave it birth
d. the speed and direction of its rotation
, e. the size of the disk around it
15. Which of these stars will take the SHORTEST time to go from the earliest protostar
stage to the main sequence?
a. a star 1/10th the mass of our Sun
b. a star ½ the mass of our Sun
c. a star equal to the mass of our Sun
d. a star ten times the mass of our Sun
e. all of these stars take the same time to get to the main sequence
Section 21.3: Evidence that Planets Form Around Other Stars
16. Which of the following is NOT one of the reasons planets around other stars are so
difficult to detect?
a. planets don't give off their own light, but only reflect the light of their stars
b. planets are small compared to stars, and so don't have much surface area from which
to reflect light
c. from far away, planets are typically lost in the glare of their parent star
d. planets have much less mass than stars
e. planets only form very late in the life of a star, just when it is ready to die, and thus last
only a very short fraction of the star's life
17. A graduate student is given the assignment to find stars with dusty disks around
them. What kind of telescope would it be best for her to use for this purpose?
a. a small telescope that detects visible light
b. a large telescope that detects infrared radiation
c. any telescope that can detect x-rays
d. an orbiting telescope that can detect ultra-violet rays
e. the students should worry; any telescope can easily show such dusty disks
18. What observations about disks of dusty material around young stars suggest that
planets may be forming in such disks?
a. the disks give off x-rays and gamma-rays characteristic of small planets
b. the disks show lanes that are empty of dust within them
c. the disks show evidence of very strong winds coming from the star
d. the disks are making the stars "wiggle" -- move back and forth across the sky -- in a
way that can be observed even with small telescopes
e. radio telescopes have revealed transmissions from the disks that include rap songs and
other evidence of advanced civilizations
Section 21.4: Planets Beyond the Solar System: Search and Discovery
