Archive for March 2019

Where would a brown dwarf be located on an H-R diagram?

Naim 14:33

Where would a brown dwarf be located on an H-R diagram? 



A) above and to the left of the highest part of the main sequence
B) in the upper right corner of the H-R diagram
C) in the lower left corner of the H-R diagram
D) below and to the right of the lowest part of the main sequence


Answer: D

We do not know for certain whether the general trends we observe in stellar birth masses also apply to brown dwarfs. But if they do, then which of the following would be true?

Naim 14:32

We do not know for certain whether the general trends we observe in stellar birth masses also apply to brown dwarfs. But if they do, then which of the following would be true? 



A) Brown dwarfs would outnumber all ordinary stars.
B) Brown dwarfs would be responsible for most of the overall luminosity of our Milky Way Galaxy.
C) Brown dwarfs would be extremely rare.
D) Most of the brown dwarfs in the Milky Way Galaxy would be quite young in age.


Answer: A

Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would you expect to be true?

Naim 14:32

Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would you expect to be true? 



A) All the stars in the cluster will be of about the same mass.
B) A few massive stars will form, live, and die before the majority of the star's clusters even complete their protostar stage.
C) All the stars in the cluster will become main-sequence stars at about the same time.
D) All the stars in the cluster will have approximately the same luminosity and surface temperature.


Answer: B

If a star is extremely massive (well over 100 solar masses), why isn't it likely to survive for long?

Naim 14:32

If a star is extremely massive (well over 100 solar masses), why isn't it likely to survive for long? 



A) It explodes as a supernova after just a few dozen years.
B) It may blow itself apart because of radiation pressure.
C) It eventually divides into two lower-mass stars.
D) Its great mass will cause it to suck itself into becoming a black hole.


Answer: B

Why does the rotation of a protostar slow down over time?

Naim 14:28

Why does the rotation of a protostar slow down over time? 



A) All rotating objects slow down over time.
B) Magnetic fields can transfer angular momentum to the protostellar disk and protostellar winds can carry angular momentum away.
C) The onset of fusion causes the rotation rate to slow dramatically.
D) Magnetic fields of other stars interact with the magnetic fields of the protostars, slowing its


Answer: B

Where does a 1-solar-mass protostar appear on an H-R diagram?

Naim 14:27

Where does a 1-solar-mass protostar appear on an H-R diagram? 



A) to the right of the main sequence, and lower down than the Sun
B) to the right of the main sequence, and higher up than the Sun
C) to the left of the main sequence, and higher up than the Sun
D) Nowhere—only stars that have fusion in their cores can be shown on H-R diagrams.


Answer: B

Generally speaking, how does the surface temperature and luminosity of a protostar compare to the surface temperature and luminosity of the main-sequence star it becomes?

Naim 14:27

Generally speaking, how does the surface temperature and luminosity of a protostar compare to the surface temperature and luminosity of the main-sequence star it becomes? 



A) A main-sequence star is hotter and brighter than it was as a protostar.
B) A main-sequence star is cooler and dimmer than it was as a protostar.
C) A main-sequence star is cooler and brighter than it was as a protostar.
D) A main-sequence star is hotter and dimmer than it was as a protostar.


Answer: D

Close binary star systems are thought to form when

Naim 14:27

Close binary star systems are thought to form when



A) two interstellar gas clouds happen to contract so close together that there's no room for a disk or planets.
B) the protostellar disk around a protostar has enough material to form a second star.
C) gravity pulls two neighboring protostars quite close together, but angular momentum causes them to orbit each other rather than colliding.
D) a protostar emits two jets, each of which turns into a star.


Answer: C

Angular momentum plays an important role in star formation. Which of the following characteristics of a protostellar system is probably not strongly affected by the star's angular momentum?

Naim 14:26

Angular momentum plays an important role in star formation. Which of the following characteristics of a protostellar system is probably not strongly affected by the star's angular momentum? 



A) the existence of protostellar jets
B) the strength of protostellar winds
C) the onset of core hydrogen fusion
D) the formation of a protostellar disk



Answer: C

According to current understanding, how did the first generation of stars differ from stars born today?

Naim 14:26

According to current understanding, how did the first generation of stars differ from stars born today? 



A) They contained much more hydrogen and helium than stars born today.
B) They were much cooler in temperature than most stars born today.
C) They were much more likely to be members of binary star systems than stars are born today.
D) They were much more massive than most stars born today.


Answer: D

Under which circumstances can you be sure that the thermal pressure within a gas cloud is increasing?

Naim 14:26

Under which circumstances can you be sure that the thermal pressure within a gas cloud is increasing? 



A) The cloud's temperature and density are both increasing.
B) The cloud's temperature is increasing and its density is decreasing.
C) The cloud's temperature and density are both decreasing.
D) The cloud's temperature is decreasing and its density is increasing.
E) It is impossible to say.


Answer: B

What happens to the visible light radiated by stars located within a dusty gas cloud?

Naim 14:25

What happens to the visible light radiated by stars located within a dusty gas cloud? 



A) It is blocked by dust and its energy is thereby lost.
B) It is absorbed by dust, which heats the dust grains so that they emit the absorbed energy as infrared light.
C) It is reflected by dust back to the star from whence it came.
D) It passes through the cloud unaffected.


Answer: B

How do we learn the chemical composition of the interstellar medium?

Naim 14:23

How do we learn the chemical composition of the interstellar medium? 



A) We make an educated guess based on the Sun's composition.
B) By studying spectra of interstellar gas clouds.
C) We collect samples of gas and dust from interstellar space.
D) We use computer simulations of the interstellar medium.


Answer: B

Which of the following statements about brown dwarfs is not true?

Naim 14:20

Which of the following statements about brown dwarfs is not true? 



A) Brown dwarfs eventually collapse to become white dwarfs.
B) Brown dwarfs are supported against gravity by degeneracy pressure, which does not depend on the object's temperature.
C) Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores.
D) All brown dwarfs have masses less than about 8% that of our Sun.


Answer: A

When does a protostar become a main-sequence star?

Naim 14:19

When does a protostar become a main-sequence star? 



A) when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space
B) when a piece of a molecular cloud first begins to contract into a star
C) when it becomes luminous enough to emit thermal radiation
D) at the instant that the first hydrogen fusion reactions occur in the protostar's core


Answer: A

What can we learn about a star from a life track on an H-R diagram?

Naim 14:19

What can we learn about a star from a life track on an H-R diagram? 



A) the star's age
B) the surface temperature and luminosity the star will have at each stage of its life
C) the star's current stage of life
D) how the star's distance from Earth varies at different times in its life


Answer: B

Which of the following phenomena is not commonly associated with the star formation process?

Naim 14:05

Which of the following phenomena is not commonly associated with the star formation process? 



A) the formation of a spinning disk of material around a protostar
B) powerful "jets" shooting out along the rotation axis of a protostar
C) strong winds of particles blowing out into space from a protostar
D) intense ultraviolet radiation coming from a protostar


Answer: D

What is a protostar?

Naim 14:04

What is a protostar? 



A) a star that has planets
B) an intermediate-mass star
C) a star that is still in the process of forming
D) a star in its final stage of life


Answer: C

Which of the following statements is probably true about the very first stars in the universe?

Naim 13:47

Which of the following statements is probably true about the very first stars in the universe? 



A) They were made only from hydrogen and helium.
B) They were made from pure energy.
C) They were probably orbited only by terrestrial planets, but no jovian planets.
D) They were made approximately of 98% hydrogen and helium, and 2% of heavier elements.


Answer: A

What effect are magnetic fields thought to have on star formation in molecular clouds?

Naim 13:46

What effect are magnetic fields thought to have on star formation in molecular clouds? 



A) They can help resist gravity, so that more total mass is needed before the cloud can collapse to form stars.
B) They accelerate the star formation process.
C) They allow small stars to form in isolation within gas clouds.
D) None—there are no magnetic fields in interstellar space.


Answer: A

Interstellar dust consists mostly of

Naim 13:27

Interstellar dust consists mostly of 



A) ozone "smog."
B) microscopic particles of carbon and silicon.
C) hydrogen and helium atoms.
D) tiny grains of water ice.
E) the same tiny particles found in household dust.


Answer: B

The interstellar clouds called molecular clouds are

Naim 13:27

The interstellar clouds called molecular clouds are 



A) the clouds in which elements such as carbon, nitrogen, and oxygen are made.
B) clouds that are made mostly of complex molecules such as carbon dioxide and sulfur dioxide.
C) the hot clouds of gas expelled by dying stars.
D) the cool clouds in which stars form.


Answer: D

What do we mean by the interstellar medium?

Naim 13:16

What do we mean by the interstellar medium? 



A) The gas and dust that lies in between the stars in the Milky Way Galaxy.
B) The dust that fills the halo of the Milky Way Galaxy.
C) The middle section of the Milky Way Galaxy.
D) The name of an oracle who can channel messages from beings that live near the star called Vega.


Answer: A

Where would a brown dwarf be located on an H-R diagram?

Naim 13:16

Where would a brown dwarf be located on an H-R diagram? 



A) upper right
B) on the lower part of the main sequence
C) below and to the right of the lowest part of the main sequence
D) lower left
E) above and to the left of the main sequence


Answer: C

What is the eventual fate of a brown dwarf?

Naim 13:16

What is the eventual fate of a brown dwarf? 



A) It remains the same forever.
B) It gradually cools down and becomes ever dimmer.
C) It gradually contracts and heats up until nuclear fusion ignites in its interior and it becomes a faint star.
D) It becomes ever denser and hotter until it becomes a white dwarf.
E) Gravity ultimately "wins" and it becomes a small black hole.


Answer: B

What prevents a brown dwarf from undergoing nuclear fusion?

Naim 13:15

What prevents a brown dwarf from undergoing nuclear fusion? 



A) Degeneracy pressure halts the contraction of a protostar so the core never becomes hot or dense enough for nuclear fusion.
B) There is not enough mass to maintain nuclear reactions in a self-sustaining way.
C) The surface temperature never rises high enough for the radiation to be trapped and heat their interior to the temperatures required for nuclear fusion.
D) Radiation pressure halts the contraction of a protostar so the core never becomes hot or dense enough for nuclear fusion.
E) There are too many heavy elements and not enough hydrogen for fusion to occur in a self-sustaining way.


Answer: A

Which of the following discoveries, if they existed, would necessitate a reevaluation of our ideas of stellar formation?

Naim 13:15

Which of the following discoveries, if they existed, would necessitate a reevaluation of our ideas of stellar formation? 



A) a cluster of stars that appeared to be 13 billion years old
B) a 100-solar-mass star
C) a 0.01-solar-mass star
D) a molecular cloud without any stars
E) planetary systems around other stars than our own


Answer: C

No stars have been found with masses greater than 300 times our Sun because

Naim 13:15

No stars have been found with masses greater than 300 times our Sun because 



A) molecular clouds do not have enough material to form such massive stars.
B) they would fragment into binary stars because of their rapid rotation.
C) they would generate so much power that they would blow themselves apart.
D) they shine exclusively at X-ray wavelengths and become difficult to detect.
E) they are not bright enough to be seen nearby.


Answer: C

What is the smallest mass a newborn star can have?

Naim 13:11

What is the smallest mass a newborn star can have? 



A) 8 times the mass of Jupiter
B) 80 times the mass of Jupiter
C) 800 times the mass of Jupiter
D) about 1/80 the mass of our Sun
E) about 1/800 the mass of our Sun


Answer: B

When does hydrogen first begin to fuse into helium in the star formation process?

Naim 13:10

When does hydrogen first begin to fuse into helium in the star formation process? 



A) when the cloud first begins to contract
B) when the thermal pressure is trapped at the center of the cloud
C) when the protostars undergoes convective contraction
D) when the protostar undergoes radiative contraction
E) only when the star reaches the main-sequence


Answer: D

What happens to the surface temperature and luminosity when a protostar radiatively contracts?

Naim 13:10

What happens to the surface temperature and luminosity when a protostar radiatively contracts? 



A) Its surface temperature and luminosity increase.
B) Its surface temperature remains the same and its luminosity decreases.
C) Its surface temperature and luminosity decrease.
D) Its surface temperature decreases and its luminosity increases.
E) Its surface temperature and luminosity remain the same.


Answer: A

What happens to the surface temperature and luminosity when a protostar undergoes convective contraction?

Naim 13:10

What happens to the surface temperature and luminosity when a protostar undergoes convective contraction? 



A) Its surface temperature and luminosity increase.
B) Its surface temperature remains the same and its luminosity decreases.
C) Its surface temperature and luminosity decrease.
D) Its surface temperature decreases and its luminosity increases.
E) Its surface temperature and luminosity remain the same.


Answer: B

What happens to the surface temperature and luminosity when gravity first assembles a protostar from a collapsing cloud?

Naim 13:10

What happens to the surface temperature and luminosity when gravity first assembles a protostar from a collapsing cloud? 



A) Its surface temperature and luminosity increase.
B) Its surface temperature remains the same and its luminosity decreases.
C) Its surface temperature and luminosity decrease.
D) Its surface temperature decreases and its luminosity increases.
E) Its surface temperature and luminosity remain the same.


Answer: A

When does a star become a main-sequence star?

Naim 13:09

When does a star become a main-sequence star? 



A) when the protostar assembles from a molecular cloud
B) the instant when hydrogen fusion first begins in the star's core
C) when the rate of hydrogen fusion within the star's core is high enough to maintain gravitational equilibrium
D) when a star becomes luminous enough to emit thermal radiation
E) when hydrogen fusion is occurring throughout a star's interior


Answer: C

What is the range of timescales for star formation?

Naim 13:08

What is the range of timescales for star formation? 



A) from 1 million years for the most massive stars up to 10 million years for the least massive stars
B) from 1 million years for the most massive stars up to 100 million years for the least massive stars
C) from 1 million years for the least massive stars up to 10 million years for the most massive stars
D) from 1 million years for the least massive stars up to 100 million years for the most massive stars
E) about 30 million years for all stars, whatever mass


Answer: B

When does a protostar become a true star?

Naim 13:08

When does a protostar become a true star? 



A) when the star is 1 million years old
B) when the central temperature reaches 1 million Kelvin
C) when nuclear fusion begins in the core
D) when the thermal energy becomes trapped in the center
E) when the stellar winds and jets blow away the surrounding material


Answer: C

Which of the following may be caused by a protostellar disk?

Naim 13:08

Which of the following may be caused by a protostellar disk? 



A) protostellar jets
B) protostellar winds
C) accretion of material onto the star
D) relatively slow protostellar rotation
E) all of the above


Answer: E

What happens to the rotation of a molecular cloud as it collapses to form a star?

Naim 13:07

What happens to the rotation of a molecular cloud as it collapses to form a star? 



A) The rotation rate remains the same and results in stellar rotation.
B) The rotation dissipates and any residual is left in small overall rotation of the star.
C) The rotation rate increases and results in fast rotation of the star.
D) The rotation rate increases and results in a disk of material around a protostar.
E) The rotation increases the speed of collapse and produces more massive stars.


Answer: D

When is thermal energy trapped in the dense center of a cloud?

Naim 13:07

When is thermal energy trapped in the dense center of a cloud? 




A) when the gravity becomes so strong that photons cannot escape
B) when excited molecules collide with other molecules before they can release a photon
C) when the cloud becomes so hot and dense that nuclear fusion begins
D) when magnetic fields trap the radiation
E) when the cloud cools down so much that less light escapes than is produced by contraction


Answer: B

Why do we think the first generation of stars would be different from stars born today?

Naim 13:07

Why do we think the first generation of stars would be different from stars born today? 



A) Without heavy elements, the clouds could not reach as low a temperature as today and had to be more massive to collapse.
B) Without heavy elements, the nuclear reactions at the center of the stars would be very different.
C) Without heavy elements, there was no dust in the clouds and they collapsed faster.
D) The Universe was much denser when the first stars were born.
E) There were no galaxies when the first stars were born.


Answer: A

What is the likely reason that we cannot find any examples of the first generation stars?

Naim 13:07

What is the likely reason that we cannot find any examples of the first generation stars? 



A) The first generation stars are too faint to be visible now.
B) The first generation stars formed such a long time ago that the light from them has not yet had time to reach us.
C) The first generation stars were all very massive and exploded as supernova.
D) The first generation stars formed with only H and He and therefore have no spectral features.
E) We do not know how the first generation stars were formed.


Answer: C

How do astronomers infer the presence of magnetic fields in molecular clouds?

Naim 13:06

How do astronomers infer the presence of magnetic fields in molecular clouds? 



A) by measuring the amount of interstellar reddening
B) by measuring the Doppler shifts of emission lines from gas clumps in the cloud
C) by measuring the infrared light emitted by the cloud
D) by measuring the polarization of starlight passing through the cloud
E) by measuring the amount by which gravity is reduced


Answer: D

What prevents the pressure from increasing as a cloud contracts due to its gravity?

Naim 13:05

What prevents the pressure from increasing as a cloud contracts due to its gravity? 



A) As the cloud becomes denser, gravity becomes stronger and overcomes the pressure buildup.
B) The pressure is transferred from the center of the cloud to its outer edges where it can dissipate.
C) Thermal energy is converted to radiative energy via molecular collisions and released as photons.
D) Excess pressure is released in jets of material from the young stars.
E) Once the cloud reaches a critical density, the pressure becomes degenerate and independent of temperature.


Answer: C

The thermal pressure of a gas depends on

Naim 13:04

The thermal pressure of a gas depends on 



A) density only.
B) temperature only.
C) density and temperature.
D) composition.
E) gravity.


Answer: C

What happens to the visible radiation produced by new stars within a molecular cloud?

Naim 13:02

What happens to the visible radiation produced by new stars within a molecular cloud? 



A) It escapes the cloud completely.
B) It is absorbed by dust grains and heats up the cloud.
C) It is reflected back onto the protostar, heating it up further.
D) The blue light is absorbed and the red light transmitted.
E) It shoots out in bright jets.


Answer: B

What is interstellar reddening?

Naim 13:02

What is interstellar reddening? 



A) Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color.
B) Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color.
C) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.
D) Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color.
E) The spectral line shift due to a star's motion through the interstellar medium.


Answer: C

The typical density and temperature of molecular clouds are

Naim 13:01

The typical density and temperature of molecular clouds are 



A) 100 molecules per cubic centimeter, 10-30 Kelvin.
B) 300 molecules per cubic centimeter, 10-30 Kelvin.
C) 1000 molecules per cubic centimeter, 10-30 Kelvin.
D) 100 molecules per cubic centimeter, 100-300 Kelvin.
E) 300 molecules per cubic centimeter, 100-300 Kelvin.


Answer: B

By mass, the interstellar medium in our region of the Milky Way consists of

Naim 13:00

By mass, the interstellar medium in our region of the Milky Way consists of 



A) 70% Hydrogen, 30% Helium.
B) 70% Hydrogen, 28% Helium, 2% heavier elements.
C) 70% Hydrogen, 20% Helium, 10% heavier elements.
D) 50% Hydrogen, 50% Helium.
E) 50% Hydrogen, 30% Helium, 20% heavier elements.


Answer: B

Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon?

Naim 12:41

Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon? 



A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude.
B) Radio astronomy would be advantageous on the Moon because human radio transmissions are less likely to cause interference, especially on the far side of the Moon.
C) It would be possible to put telescopes for ultraviolet and X-ray astronomy on the surface, unlike the case on the surface of the Earth.
D) Telescopes on the Moon could observe stars even when it is daytime on the Moon.


Answer: A

Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images?

Naim 12:40

Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images?


 (Assume all else is equal, such as quality of optics, types of instruments, and so on.)


A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
B) Observatory Y can detect dimmer stars and Observatory X reveals more detail in images.
C) Observatory X both detects dimmer stars and reveals more detail in images.
D) Observatory Y both detects dimmer stars and reveals more detail in images.


Answer: A

The Chandra X-Ray Observatory must operate in space because

Naim 12:40

The Chandra X-Ray Observatory must operate in space because 



A) X rays are too dangerous to be allowed on the ground.
B) X rays do not penetrate Earth's atmosphere.
C) X-ray telescopes require the use of grazing incidence mirrors.
D) It was built by NASA.


Answer: B

The stars in our sky twinkle in brightness and color because of

Naim 12:39

The stars in our sky twinkle in brightness and color because of 



A) turbulence in the Earth's atmosphere.
B) rapid changes in the brightnesses and colors of stars caused by changes in their spectra.
C) light pollution.
D) the bubbling and boiling of gases on the surfaces of stars.


Answer: A

Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?

Naim 12:39

Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? 



A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
B) Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence.
C) Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations.
D) Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities.


Answer: A

Which of the following studies is best suited to astronomical observations that fall into the category called timing?

Naim 12:39

Which of the following studies is best suited to astronomical observations that fall into the category called timing? 



A) studying how different planets differ in their surface compositions
B) studying how a star's brightness varies over a period of 3 years
C) measuring the rotation rate of a distant star
D) determining the age of the solar system


Answer: B

Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light?

Naim 12:39

Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? 



A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
B) Radio telescopes are designed to collect sound rather than light.
C) It is because radio telescopes are used in the daytime and visible light telescopes are used at night.
D) Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes.


Answer: A

Which of the following best describes the development of astronomical telescopes over the past 60 years?

Naim 12:38

Which of the following best describes the development of astronomical telescopes over the past 60 years? 



A) Over the 60-year period, telescopes have gradually gotten bigger and more powerful.
B) Although there have been advances in cameras and computing power, telescopes themselves have not changed much in the last 60 years.
C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
D) The only major change in telescope power has occurred because of our ability to launch telescopes into space rather than operating them only from the ground.


Answer: C

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?

Naim 12:38

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? 



A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
B) The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope.
C) The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope.
D) The answer cannot be determined from the information given in the question.


Answer: A

Which of the following best describes the principle advantage of CCDs over photographic film?

Naim 12:36

Which of the following best describes the principle advantage of CCDs over photographic film? 



A) CCDs allow long exposures (e.g., minutes or hours) and film does not.
B) CCDs capture a much higher percentage of the incoming photons than film.
C) CCDs can record the colors of astronomical objects accurately while film cannot.
D) CCDs can be attached to modern telescopes more easily than can photographic film.


Answer: B

Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope?

Naim 12:36

Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope?



A) The photograph will have far better angular resolution than you can see with your eye.
B) By using a long exposure time, the photograph can allow you to see objects that would be too dim to see with your eye.
C) If taken with a camera with a sensitive detector such as a CCD, the photograph can capture a much larger percentage of the incoming photons than can your eye.
D) The photograph provides a more reliable record of what is seen through the telescope than can a drawing made by eye.


Answer: A

The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?

Naim 12:35

The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? 



A) The two stars will appear to be touching, looking rather like a small dumbbell.
B) The stars will not show up at all in your photograph.
C) The photo will seem to show only one star rather than two.
D) You will see two distinct stars in your photograph.

Answer: C

Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?

Naim 12:34

Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true? 



A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.
B) The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp.
C) Both photographs have the same angular resolution, because they were both printed at the same sizes in each case.
D) Both photographs have the same angular resolution, because they are both photographs of the same object.


Answer: A

What is the purpose of interferometry?

Naim 12:34

What is the purpose of interferometry? 



A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
B) It allows two or more small telescopes to achieve a larger light-collecting area than they would have independently.
C) t is designed to prevent light pollution from interfering with astronomical observations.
D) It reduces the twinkling of stars caused by atmospheric turbulence.


Answer: A

Which of the following wavelength regions can be studied with telescopes on the ground?

Naim 12:34

Which of the following wavelength regions can be studied with telescopes on the ground? 



A) radio, visible, and very limited portions of the infrared and ultraviolet regions
B) all light with wavelengths longer than ultraviolet wavelengths
C) all light with wavelengths shorter than infrared wavelengths
D) infrared, visible, and ultraviolet light


Answer: A

What is the purpose of adaptive optics?

Naim 12:34

What is the purpose of adaptive optics? 



A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
B) It allows several small telescopes to work together like a single larger telescope.
C) It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects.
D) It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere.


Answer: A

What do astronomers mean by light pollution?

Naim 12:33

What do astronomers mean by light pollution? 



A) Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium.
B) Light pollution is light from human sources that makes it difficult to see the stars at night.
C) Light pollution means contamination of light caused by chemicals in the Earth's atmosphere.
D) Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.


Answer: B

Which of the following is always true about images captured with X-ray telescopes?

Naim 12:33

Which of the following is always true about images captured with X-ray telescopes? 



A) They are always shown with colors that are not the true colors of the objects that were photographed.
B) They always are made with adaptive optics.
C) They show us light with extremely long wavelengths compared to the wavelengths of visible light.
D) They always have very high angular resolution.
E) They are always very pretty.


Answer: A

Which of the following is not one of the three main categories of observation generally used by astronomers?

Naim 12:32

Which of the following is not one of the three main categories of observation generally used by astronomers? 



A) filtering to look at just a single color from an object
B) timing to track how an object's brightness varies with time
C) spectroscopy to spread an object's light into a spectrum
D) imaging to get a picture of an astronomical objects


Answer: A

What do we mean by the diffraction limit of a telescope?

Naim 12:32

What do we mean by the diffraction limit of a telescope? 



A) It describes the farthest distance to which the telescope can see.
B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
C) It is the maximum size to which any telescope can be built.
D) It describes the maximum exposure time for images captured with the telescope.


Answer: B

Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?

Naim 12:32

Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope? 



A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
B) A refracting telescope produces refracted images while a reflecting telescope produces reflected images.
C) Reflecting telescopes make much clearer images than can refracting telescopes of the same size.
D) It is much easier to make a large refracting telescope than a large reflecting telescope.


Answer: A

What is a CCD?

Naim 12:32

What is a CCD? 



A) It is an electronic detector that can be used in place of photographic film for making images.
B) It is an abbreviation for the world's largest operating telescope.
C) It refers to any kind of instrument that can be hooked up to a telescope.
D) It is a unit used by astronomers to measure angular resolution.


Answer: A

What is the angular resolution of the human eye?

Naim 12:32

What is the angular resolution of the human eye? 



A) about 1 degree
B) about 1 arcsecond (1/3600 of a degree)
C) about 1 arcminute, or 1/60 of a degree
D) about 1 milliarcsecond


Answer: C

What does angular resolution measure?

Naim 12:31

What does angular resolution measure? 



A) the angular size of the smallest features that the telescope can see
B) the brightness of an image
C) the size of an image
D) the number of electromagnetic waves captured by an image


Answer: A

Which of the following best describes what we mean by the focal plane of a telescope?

Naim 12:31

Which of the following best describes what we mean by the focal plane of a telescope? 



A) It is the upper surface of the telescope's primary lens or mirror.
B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
C) It is the lower surface of the telescope's primary lens or mirror.
D) It is the surface of the lens on the eyepiece, through which you would look to see objects in the telescope's field of view.


Answer: B

What does the technique of interferometry allow?

Naim 12:30

What does the technique of interferometry allow? 



A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light-collecting area of the individual telescopes.
B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
C) It allows us to determine the chemical composition of stars.
D) It allows astronomers to make astronomical observations without interference from light pollution.
E) It allows the same telescope to make images with both radio waves and visible light.


Answer: B

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

Naim 12:28

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? 



A) It is closer to the stars.
B) Stars do not twinkle when observed from space.
C) It can observe infrared and ultraviolet light, as well as visible light.
D) It never has to close because of bad weather.
E) Observers on the ground can use it at any time of day (i.e., not only during their night).


Answer: A

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

Naim 12:28

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? 



A) New telescopes incorporate new technology to increase their efficiency.
B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths.
C) Photons of different energy behave differently and require different collection strategies.
D) Light pollution is worse at radio wavelengths than visible wavelengths.
E) Astronomers and engineers enjoy the challenge of making new telescope designs.


Answer: C

What is an artificial star?

Naim 12:28

What is an artificial star? 



A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations
B) a satellite orbiting Earth
C) a meteor
D) a possible source of dark matter in the universe
E) the unseen member of a binary star system


Answer: A

What is the purpose of adaptive optics?

Naim 12:27

What is the purpose of adaptive optics? 



A) to improve the angular resolution of telescopes in space
B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
C) to increase the collecting area of telescopes on the ground
D) to increase the magnification of telescopes on the ground
E) to allow several small telescopes to work together like a single larger telescope


Answer: B

What causes stars to twinkle?

Naim 12:26

What causes stars to twinkle? 



A) It is intrinsic to the stars-their brightness varies as they expand and contract.
B) variations in the absorption of the atmosphere
C) variable absorption by interstellar gas along the line of sight to the star
D) bending of light rays by turbulent layers in the atmosphere
E) the inability of the human eye to see faint objects


Answer: D

What do astronomers mean by light pollution?

Naim 12:25

What do astronomers mean by light pollution? 



A) Light pollution refers to pollution caused by light industry as opposed to heavy industry.
B) Light pollution refers to harmful gases emitted by common street lights.
C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
D) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness.
E) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime.


Answer: C

Which of the following is always true about images captured with X-ray telescopes?

Naim 12:25

Which of the following is always true about images captured with X-ray telescopes? 



A) They are always very pretty.
B) They are always displayed with the highest possible angular resolution.
C) They are always useful for seeing through things.
D) They are always displayed in false color.
E) They are always displayed with north pointing upward in the images.


Answer: D

Which of the following studies is best suited to a time monitoring experiment?

Naim 12:25

Which of the following studies is best suited to a time monitoring experiment? 



A) studying how different stars differ in their chemical compositions
B) studying whether a particular star's brightness is steady or variable
C) determining the age of the solar system
D) measuring the rotation rate of a distant star
E) estimating the time since the Big Bang


Answer: B

What is meant by spectral resolution?

Naim 12:25

What is meant by spectral resolution? 



A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum.
B) It is a measure of how close two spectral lines can be distinguished.
C) It is a measure of how close two point sources can be distinguished.
D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.


Answer: B

Which of the following could not be measured by an observation that uses only imaging?

Naim 12:24

Which of the following could not be measured by an observation that uses only imaging? 



A) the rate at which a variable star brightens and dims
B) the general shape of an interstellar cloud of gas
C) the color of a planet
D) the brightness of a star in our sky
E) the number of bright stars in a nearby star cluster


Answer: A

What do we mean by the diffraction limit of a telescope?

Naim 12:24

What do we mean by the diffraction limit of a telescope? 



A) It is the maximum size to which any telescope can be built.
B) It describes the farthest distance to which the telescope can see.
C) It describes the maximum exposure time for images captured with the telescope.
D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.


Answer: D

Which of the following statements best describes the two principal advantages of telescopes over eyes?

Naim 12:24

Which of the following statements best describes the two principal advantages of telescopes over eyes? 



A) Telescopes can collect far more light with far better angular resolution.
B) Telescopes can collect far more light with far greater magnification.
C) Telescopes have much more magnification and better angular resolution.
D) Telescopes collect more light and are unaffected by twinkling.
E) Telescopes can see farther without image distortion and can record more accurate colors.


Answer: A

Which of the following is a principal advantage of CCDs over photographic film?

Naim 12:23

Which of the following is a principal advantage of CCDs over photographic film? 



A) CCDs allow long exposures (e.g., minutes or hours), and film does not.
B) CCDs can record the colors of astronomical objects accurately, while film cannot.
C) CCDs capture a much higher percentage of the incoming photons than does film.
D) Images recorded with CCDs never require any image processing, while images recorded by film often do.
E) CCDs can be attached to modern telescopes more easily than cameras.


Answer: C

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?

Naim 12:23

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? 



A) You will not be able to see these two stars at all.
B) The two stars will look like a single point of light.
C) The two stars will appear to be touching, looking rather like a small dumbbell.
D) You will see two distinct stars.
E) You will see only the larger of the two stars, not the smaller one.


Answer: B

Which of the following statements about light focusing is not true?

Naim 12:23

Which of the following statements about light focusing is not true? 



A) In a healthy eye, light is focused on the retina.
B) Film should be placed at the focal plane in a camera.
C) If you try to look at an image that is not formed at the focal plane, it will be blurry.
D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.
E) Light can be focused with a lens or a mirror.


Answer: D

Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?

Naim 12:20

Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number? 



A) atomic number = 6; atomic mass number = 13
B) atomic number = 6; atomic mass number = 7
C) atomic number = 13; atomic mass number = 6
D) atomic number = 7; atomic mass number = 13


Answer: A

Suppose that two stars are identical in every way—for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth—except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?

Naim 12:19

Suppose that two stars are identical in every way—for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth—except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart? 



A) The faster rotating star has wider spectral lines than the slower rotating star.
B) The faster rotating star will have an emission line spectrum while the slower rotating star will have an absorption line spectrum.
C) The peak of thermal emission will be at a shorter wavelength for the faster rotating star than for the slower rotating star.
D) There is no way to tell the stars apart spectroscopically, because their spectra will be identical.


Answer: A

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?

Naim 12:19

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true? 



A) The total amount of light in the spectrum tells us the star's radius.
B) The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.
C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.
D) Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us.


Answer: A

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

Naim 12:14

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet? 



A) We must actually be observing moons orbiting the planet in opposite directions, not the planet itself.
B) The planet is rotating.
C) The planet is in the process of falling apart.
D) The planet is in the process of formation.


Answer: B

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

Naim 07:28

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude? 



A) Star X is moving away from us faster than Star Y.
B) Star Y is moving away from us faster than Star X.
C) Star X is hotter than Star Y.
D) Star X is moving away from us and Star Y is moving toward us.


Answer: A

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

Naim 07:27

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude? 




A) The star is moving away from us.
B) The star is getting hotter.
C) The star is moving toward us.
D) The star is getting colder.


Answer: C

All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?

Naim 07:27

All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays? 



A) The temperature of the corona's gas is some 1 to 2 million Kelvin.
B) The corona lies above the visible surface of the Sun.
C) The corona's gas consists mostly of hydrogen and helium.
D) The corona's structure is largely shaped by magnetic fields.


Answer: A

The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?

Naim 07:27

The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun? 



A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
B) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the blue light that is present in the Sun's spectrum.
C) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum.
D) There is no way to predict the answer to this question, since planets and stars are made of such different things.


Answer: A

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

Naim 07:27

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color? 



A) It is much brighter than the Sun.
B) Its surface is cooler than the surface of the Sun.
C) It is much more massive than the Sun.
D) It is moving away from us.


Answer: B

Which of the following statements about thermal radiation is always true?

Naim 07:26

Which of the following statements about thermal radiation is always true? 



A) A hot object emits more radiation per unit surface area than a cool object.
B) A cold object produces more total infrared and radio emission per unit surface area than a hot object.
C) A hot object produces more total infrared emission than a cooler object.
D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.


Answer: A

No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?

Naim 07:26

No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum? 



A) a hot, thin (low-density, nearly transparent) gas
B) a filament in a standard (incandescent) light bulb
C) a star
D) you


Answer: A

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

Naim 07:26

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? 



A) The cloud is extremely hot.
B) The cloud is visible primarily because it reflects light from nearby stars.
C) The cloud is cool and very dense, so that you cannot see any objects that lie behind it.
D) The cloud is cool and lies between you and a hot star.


Answer: D

Which of the following statements about electrons is not true?

Naim 07:26

Which of the following statements about electrons is not true? 



A) Electrons orbit the nucleus rather like planets orbiting the Sun.
B) Within an atom, an electron can have only particular energies.
C) An electron has a negative electrical charge.
D) Electrons have very little mass compared to protons or neutrons.
E) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.


Answer: A

Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?

Naim 07:25

Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion? 



A) Charge = +2; number of remaining electrons = 8.
B) Charge = -2; number of remaining electrons = 10.
C) Charge = +2; number of remaining electrons = 6.
D) Charge = +2; number of remaining electrons = 2


Answer: C

Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?

Naim 07:19

Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature? 



A) It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
B) The liquid molecules would quickly dissociate into a liquid of individual oxygen atoms. These atoms would then evaporate into a gas, and then become ionized to make a plasma.
C) It would sublimate into a gas, then the molecules would lose electrons until no electrons were left, then the molecules would dissociate into individual oxygen nuclei.
D) The cold temperature would first cause the oxygen to solidify. The solid would then sublimate into a gas, which would then become a plasma as the molecules lost their electrons, until finally it consisted of bonded pairs of oxygen nuclei stripped bare of any electrons.


Answer: A

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?

Naim 07:18

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element? 



A) Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons;
Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons.
B) Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons;
Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons.
C) Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons;
Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons.
D) Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons;
Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons.


Answer: B

Which of the following statements about X rays and radio waves is not true?

Naim 07:17

Which of the following statements about X rays and radio waves is not true? 



A) X rays travel through space faster than radio waves.
B) X rays have shorter wavelengths than radio waves.
C) X rays and radio waves are both forms of light, or electromagnetic radiation.
D) X rays have higher frequency than radio waves.


Answer: A

Which of the following best describes why we say that light is an electromagnetic wave?

Naim 07:16

Which of the following best describes why we say that light is an electromagnetic wave? 



A) Light can be produced only by electric or magnetic appliances.
B) Light is produced only when massive fields of electric and magnetic energy collide with one another.
C) The passage of a light wave can cause electrically charged particles to move up and down.
D) The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.


Answer: C

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