astro ch 4

Question 1

If you see the color red in an X-ray image from the Chandra X-Ray Observatory, it means:

Answer 1

it depends: the colors are chosen arbitrarily to represent something about the X rays recorded by the telescope

Question 2

Suppose that two stars in a binary star system are separated by a distance of 70 million kilometers and are located at a distance of 130 light-years from Earth. What is the angular separation of the two stars? Give your answer in degrees.

Answer 2

θ = 3.3×10−6∘

Question 3

What do astronomers mean by light pollution?

Answer 3

Light pollution is light from human sources that makes it difficult to see the stars at night.

Question 4

Astronomers have begun to build instruments to detect “cosmic messengers” that are not forms of light, such as neutrinos, cosmic rays, and gravitational waves, because they

Answer 4

provide information about distant objects that we cannot obtain from light

Question 5

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

Answer 5

Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.

Question 6

What is the purpose of adaptive optics?

Answer 6

It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

Question 7

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?

Answer 7

The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.

Question 8

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

Answer 8

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

Question 9

Suppose you have a camera attached to a telescope, and you want to record an image of a faint galaxy. Which of the following will help the most?

Answer 9

a lot of pixels and a long exposure time

Question 10

Why can’t x-ray and gamma-ray telescopes use the same designs as visible-light telescopes?

Answer 10

X-rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.

Question 11

The twinkling of stars is caused by:

Answer 11

motion of air in our atmosphere

Question 12

How much greater is the light-collecting area of one of the 10-meter Keck telescopes than that of the 5-meter Hale telescope?

Answer 12

4

Question 13

Suppose astronomers built a 140-meter telescope. How much greater would its light-collecting area be than that of the 10-meter Keck telescope?

Answer 13

200

Question 14

The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is:

Answer 14

above Earth’s atmosphere.

Question 15

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

Answer 15

Filtering to look at just a single color from an object.

Question 16

Suppose you were looking at our own solar system from a distance of 15 light-years. What angular resolution would you need to see the Sun and Jupiter as distinct points of light?

Answer 16

θJupiter = 1.1′′

Question 17

When your eye forms an image, the _____ plays a role analogous to the detector in a camera.

Answer 17

retina

Question 18

The Chandra X-ray Observatory must operate in space because

Answer 18

x-rays do not penetrate Earth’s atmosphere

Question 19

What does angular resolution measure?

Answer 19

The angular size of the smallest features that the telescope can see

Question 20

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?

Answer 20

The photo will seem to show only one star rather than two.