Question 1

Explain how adaptive optics works.

Accepted Answer

Adaptive optics corrects for atmospheric distortion by following the distortion of a bright star,possibly an artificial star created by a laser,and rapidly changing the shape of a mirror using computer-controlled actuators to compensate for the distortion.

Question 2

What do astronomers mean by light pollution?

Accepted Answer

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. 
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. C

Question 3

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

Accepted Answer

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). 
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). A

Question 4

The diffraction-limited resolution of a 10-meter telescope is about 0.01 arcsecond for visible light.Would you expect the angular resolution of a 20-meter space telescope observing visible light to be better than,equal to,or worse than 0.01 arcsecond? Explain.

Accepted Answer

It would be better than 0.01 arcsecond b

Question 5

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. )

Accepted Answer

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. 
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.

Question 6

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

Accepted Answer

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 cloudy skies. 
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 cloudy skies.

Question 7

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

Accepted Answer

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. 
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.

Question 8

What do astronomers mean by light pollution?

Accepted Answer

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. 
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.

Question 9

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?

Accepted Answer

A) radio 
B) infrared 
C) visible 
D) ultraviolet 
E) X-ray 
A) radio 
B) infrared 
C) visible 
D) ultraviolet 
E) X-ray

Question 10

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

Accepted Answer

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 have different wavelengths,some of which are not accessible from Earth's surface 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. 
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 have different wavelengths,some of which are not accessible from Earth's surface 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.

Question 11

Which of the following is not a good reason to place observatories on remote mountain tops?

Accepted Answer

A) to reduce light pollution 
B) to reduce light distortion 
C) to reduce light absorption 
D) to be able to observe at radio wavelengths 
E) to be able to observe at infrared wavelengths 
A) to reduce light pollution 
B) to reduce light distortion 
C) to reduce light absorption 
D) to be able to observe at radio wavelengths 
E) to be able to observe at infrared wavelengths

Question 12

What is meant by spectral resolution?

Accepted Answer

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. 
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.

Question 13

Why is it important that the James Webb Space Telescope will be operating in the infrared?

Accepted Answer

A) It will allow us to study the highly redshifted light of distant galaxies,enabling us to observe them as they first formed in the early universe. 
B) The infrared is not easily visible from Earth's surface. 
C) It will allow us to be closer to the most distant galaxies,so we get better pictures. 
D) It will allow us to see into other universes that are not visible from Earth's surface. 
A) It will allow us to study the highly redshifted light of distant galaxies,enabling us to observe them as they first formed in the early universe. 
B) The infrared is not easily visible from Earth's surface. 
C) It will allow us to be closer to the most distant galaxies,so we get better pictures. 
D) It will allow us to see into other universes that are not visible from Earth's surface.

Question 14

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

Accepted Answer

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. 
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.

Question 15

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?

Accepted Answer

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. 
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.

Question 16

Which of the following could not be determined by an observation that uses only spectroscopy?

Accepted Answer

A) the chemical composition of a distant star 
B) the speed at which a distant galaxy is moving away from us 
C) the surface temperature of a distant star 
D) the rotation rate of a distant star 
E) the size of a distant galaxy 
A) the chemical composition of a distant star 
B) the speed at which a distant galaxy is moving away from us 
C) the surface temperature of a distant star 
D) the rotation rate of a distant star 
E) the size of a distant galaxy

Question 17

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

Accepted Answer

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. 
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.

Question 18

At which wavelength range is there no current or planned space observatory?

Accepted Answer

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

Question 19

Which of the following wavelength regions cannot be studied with telescopes on the ground?

Accepted Answer

A) radio waves 
B) ultraviolet 
C) X-rays 
D) both B and C 
E) both A and C 
A) radio waves 
B) ultraviolet 
C) X-rays 
D) both B and C 
E) both A and C

Question 20

The James Webb Space Telescope is scheduled to launch in 2018.In what range of the electromagnetic spectrum will it operate?

Accepted Answer

A) X-ray 
B) Gamma-ray 
C) Infrared 
D) Radio 
A) X-ray 
B) Gamma-ray 
C) Infrared 
D) Radio

Exam 6: Telescopes: Portals of Discovery

Explain how adaptive optics works.

What do astronomers mean by light pollution?

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

The diffraction-limited resolution of a 10-meter telescope is about 0.01 arcsecond for visible light.Would you expect the angular resolution of a 20-meter space telescope observing visible light to be better than,equal to,or worse than 0.01 arcsecond? Explain.

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

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

What do astronomers mean by light pollution?

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?

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

Which of the following is not a good reason to place observatories on remote mountain tops?

What is meant by spectral resolution?

Why is it important that the James Webb Space Telescope will be operating in the infrared?

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

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?

Which of the following could not be determined by an observation that uses only spectroscopy?

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

At which wavelength range is there no current or planned space observatory?

Which of the following wavelength regions cannot be studied with telescopes on the ground?

The James Webb Space Telescope is scheduled to launch in 2018.In what range of the electromagnetic spectrum will it operate?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light and Matter: Reading Messages from the Cosmos

Our Planetary System

Formation of the Solar System

Planetary Geology: Earth and the Other Terrestrial Worlds

Planetary Atmospheres: Earth and the Other Terrestrial Worlds

Jovian Planet Systems

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: The New Science of Distant Worlds

Our Star

Surveying the Stars

Star Birth

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

Galaxies and the Foundations of Modern Cosmology

Galaxy Evolution

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Celestial Timekeeping and Navigation

Space and Time

Spacetime and Gravity

Building Blocks of the Universe

Filters