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Unit 4 Review Game Questions
1. Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How
will the stars appear to your eyes?
2. List 4 advantages of CCDs over photographic film.
3. What are the two principal advantages of telescopes over eyes?
4. Currently, the largest optical telescope mirrors have a diameter of ___________.
5. Identify the type of observation involved in determining the number of bright stars in a nearby star
cluster.
6. Identify the type of observation involved in determining whether a particular star’s brightness is
steady or variable.
7. Identify the type of observation involved in determining the rotation rate of a distant star.
8. Identify the type of observation involved in determining the brightness of a star in our sky.
9. Identify the type of observation involved in determining the size of a distant galaxy.
10. Identify the type of observation involved in determining the surface temperature of a distant star.
11. How is it possible for us to see images captured with X-ray telescopes?
12. What do astronomers mean by light pollution?
13. What causes stars to twinkle?
14. What is the purpose of adaptive optics?
15. Why do astronomers need different telescope designs to observe across the electromagnetic
spectrum?
16. List 4 advantages of the Hubble Space Telescope over ground-based telescopes.
17. Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
18. At which wavelength range is there no current or planned space observatory?
19. In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
20. In what wavelength range was interferometry first routinely used?
21. Rank the human eye, CCD and photographic film in order of increasing efficiency of detecting
photons of visible light.
22. What is an artificial star?
23. What does the technique of interferometry allow?
24. Very accurate measurements of stellar brightness and sudden changes are made with a
___________.
25. The resolution of a mirror depends directly on the ________ of the main mirror.
26. The angular size of the object detected by a telescope is called its ________.
27. _______ was a technique first used successfully with long radio waves to combine the signals of two
or more reflectors to greatly enhance the resolution of the array.
28. Ultraviolet astronomy must be done in space, since the ________ layer blocks these energies from
reaching the Earth's surface well.
29. ________ optics deform the shape of a mirror in phase with changes in the seeing.
30. When used as a single instrument to greatly enhance resolution, the four mirrors of the VLT act as a
(n) ________.
31. Modern telescopes have greatly increased their ability to focus the faintest, most distant galaxies
with the use of ________ for digital imaging.
32. Mirages, the twinkling of starlight, and the use of lenses to focus light all depend on the ________ of
light waves.
33. The ________ Observatory focuses X-rays in Space much as Hubble focuses light.
34. Suppose the two stars in a system are separated by a distance of 75 million kilometers. They are
located a distance of 100 light years from the Earth. What is the angular separation of the two stars?
Can the Hubble Space Telescope resolve these 2 stars? (Hint: The angular resolution of Hubble is
0.05″)
35. Draw and label a simple diagram of a refracting telescope.
36. Draw and label a simple diagram of a reflecting telescope.
37. Describe what adaptive optics are designed to overcome and explain how adaptive optics works.
38. Explain what an interferometer is and describe how interferometers works. Give an example of an
interferometer.
39. Identify the type of observation involved in determining how stars differ in their chemical
composition.
40. Identify the type of observation involved in determining the number of bright stars in a nearby star
cluster.
41. Identify the type of observation involved in determining the general shape of an interstellar cloud.
42. List 4 reasons why a mountaintop is a good site for a telescope.
43. ___________ is the tendency of a wave to bend as it passes from one transparent medium to another.
44. What is the primary purpose of an astronomical telescope?
45. List 3 reasons why most large telescopes are reflectors, not refractors.
46. It is diffraction that limits the ____ of a scope of a given size.
47. In _____ experiments, a prism or diffraction grating is used to analyze starlight, giving us the
temperature, motion and composition of an astronomical object.
48. _______ optics deform the shape of a mirror in phase with changes in seeing.
49. In a healthy eye, light is focused on the _______.
50. Infrared, ultraviolet, x-ray and _____ light are best studied using a space telescope.
51. Because of _______ , images in small telescopes are more blurred than images with larger
objectives.
52. What is spectral resolution? Explain why a large telescope allows for a higher spectral resolution
that a smaller telescope.
Unit 4 Review Game Answers
1. The two stars will look like a single point of light.
2. CCDs are more light efficient, they capture a much higher percentage of the incoming photons, the
digital data can be stored & transmitted and CCDs don’t have to be developed like film does.
3. Telescopes can collect far more light with far better angular resolution.
4. 10 m
5. Imaging
6. Timing
7. Spectroscopy
8. Imaging
9. Imaging
10. Spectroscopy
11. They are always displayed in false color.
12. Light pollution refers to light used for human activities that brightens the sky and hinders
astronomical observations.
13. bending of light rays by turbulent layers in the atmosphere
14. to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
15. Photons of different energy behave differently and require different collection strategies.
16. Observers on the ground can use it at any time of day (i.e., not only during their night).
It never has to close because of bad weather.
Stars do not twinkle when observed from space.
It can observe infrared and ultraviolet light, as well as visible light.
17. extreme infrared
18. radio
19. radio
20. radio
21. eye, photographic film, CCD
22. a point of light in the earth's atmosphere created by a laser for the purpose of monitoring
atmospheric fluctuations
23. It allows two or more telescopes to obtain the angular resolution of a single telescope much larger
than any of the individual telescopes.
24. photometer.
25. diameter
26. resolution
27. Interferometry
28. ozone
29. Adaptive
30. interferometer
31. CCDs
32. refraction
33. Chandra
34. given: separation distance = 75 million km = 75 x 106 km and distance = 100 light years
first find the distance in km,
100 𝑙𝑦 𝑥
9.46𝑥1012 𝑘𝑚
1 𝑙𝑦
= 9.46 x1014 km
Now, find the angular separation,
360
3600″
angular separation = physical separation (2 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒) (
1
)
206,265″
angular separation = physical separation(𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 )
206,265″
angular separation = 75 x 106 km(9.46𝑥1014 𝑘𝑚)= 0.016″
This is smaller than the resolution for Hubble, so the telescope cannot resolve it.
35. Refracting Telescope diagram:
36. Reflecting Telescope Diagram:
37. Adaptive optics corrects for distortions in an image created by atmospheric turbulence. Computers
monitor the distortion of a bright star, possibly an artificial star created by a laser. They rapidly
change the shape of a mirror using computer-controlled actuators to compensate for the distortion
creating a clearer image.
38. Interferometers are groups of telescopes that have been linked together. Their light waves interfere
or combine with each other which allow them to achieve the same angular resolution (but not the
collecting area) as a much larger telescope. Interferometry is primarily used for radio telescopes like
the Very Large Array in New Mexico. The VLA links 27 telescopes, each the size of a large house,
over tens of miles.
39. spectroscopy
40. imaging
41. imaging
42. you are above the carbon dioxide and water vapor in the atmosphere (less absorption)
less air above you means better seeing because there’s less turbulence so there’s less light distortion
there is less light pollution
can observe at infrared wavelengths
43. refraction
44. to collect a lot of light and bring it to a focus
45. large, clear lenses are harder to cast than large mirror blanks
large lenses deform under their own weight
lenses require two surfaces, mirrors only require one surface
46. resolution
47. spectroscopy
48. Adaptive
49. retina
50. gamma ray
51. diffraction
52. Spectral resolution is a measure of the amount of detail the can be seen in the spectrum of an object,
for example how well two closely spaced absorption lines can be separated. It depends on how
widely the light from a telescope s spread out. However, the trade-off is that the more the light is
spread out, the dimmer it becomes until it becomes undetectable. Since large telescopes can collect
more light, they can spread the light out and achieve higher resolution than a smaller telescope.