Chapter 6

In what wavelength range was interferometry first routinely used? A) radio B) infrared C) optical D) ultraviolet E) X-ray

A) radio

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? A) radio B) infrared C) visible D) ultraviolet E) X-ray

A) radio

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).

A) It is closer to the stars.

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.

A) Telescopes can collect far more light with far better angular resolution.

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

A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations

Order the following in order of increasing efficiency of detecting photons of visible light. A) eye, photographic film, CCD B) photographic film, CCD, eye C) CCD, eye, photographic film D) CCD, photographic film, eye E) eye, CCD, photographic film

A) eye, photographic film, CCD

At which wavelength range is there no current or planned space observatory? A) radio B) infrared C) visible D) X-ray E) gamma-ray

A) radio

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

A) the rate at which a variable star brightens and dims

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.

B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.

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.

B) It is a measure of how close two spectral lines can be distinguished.

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.

B) The two stars will look like a single point of light.

Telescopes operating at this wavelength must be cooled to observe faint astronomical objects. A) radio B) extreme infrared C) visible D) X-ray E) gamma-ray

B) extreme infrared

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

B) studying whether a particular star's brightness is steady or variable

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

B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground

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.

C) CCDs capture a much higher percentage of the incoming photons than does film.

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.

C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.

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.

C) Photons of different energy behave differently and require different collection strategies.

Currently, the largest optical telescope mirrors have a diameter of A) 1 m. B) 2 m. C) 5 m. D) 10 m. E) 100 m.

D) 10 m.

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.

D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.

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.

D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.

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.

D) They are always displayed in false color.

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

D) bending of light rays by turbulent layers in the atmosphere

Which of the following wavelength regions cannot be studied with telescopes on the ground? A) radio waves B) ultraviolet C) X rays D) both B and C E) both A and C

D) both B and C

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

D) to be able to observe at radio wavelengths

The largest effective telescope, created by radio interferometry, is the size of A) several football fields, in a natural depression in Puerto Rico. B) tens of miles across, in the deserts of New Mexico. C) the state of New Mexico. D) the continental United States. E) Earth.

E) Earth.

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

E) the size of a distant galaxy