6.12.1: Review Questions
Review Questions
What are the three basic components of a modern astronomical instrument? Describe each in one to two sentences.
2.
Name the two spectral windows through which electromagnetic radiation easily reaches the surface of Earth and describe the largest-aperture telescope currently in use for each window.
3.
List the largest-aperture single telescope currently in use in each of the following bands of the electromagnetic spectrum: radio, X-ray, gamma ray.
4.
When astronomers discuss the apertures of their telescopes, they say bigger is better. Explain why.
5.
The Hooker telescope at Palomar Observatory has a diameter of 5 m, and the Keck I telescope has a diameter of 10 m. How much more light can the Keck telescope collect than the Hooker telescope in the same amount of time?
6.
What is meant by “reflecting” and “refracting” telescopes?
7.
Why are the largest visible-light telescopes in the world made with mirrors rather than lenses?
8.
Compare the eye, photographic film, and CCDs as detectors for light. What are the advantages and disadvantages of each?
9.
What is a charge-coupled device (CCD), and how is it used in astronomy?
10.
Why is it difficult to observe at infrared wavelengths? What do astronomers do to address this difficulty?
11.
Radio and radar observations are often made with the same antenna, but otherwise they are very different techniques. Compare and contrast radio and radar astronomy in terms of the equipment needed, the methods used, and the kind of results obtained.
12.
Look back at Figure 6.18 of Cygnus A and read its caption again. The material in the giant lobes at the edges of the image had to have been ejected from the center at least how many years ago?
13.
Why do astronomers place telescopes in Earth’s orbit? What are the advantages for the different regions of the spectrum?
14.
What was the problem with the Hubble Space Telescope and how was it solved?
15.
Describe the techniques radio astronomers use to obtain a resolution comparable to what astronomers working with visible light can achieve.
16.
What kind of visible-light and infrared telescopes on the ground are astronomers planning for the future? Why are they building them on the ground and not in space?
17.
Describe one visible-light or infrared telescope that astronomers are planning to launch into space in the future.