CH 05

If you want to make a very dim object appear much brighter in an image photographed through a telescope, which of the following factors are important?

Which of the following is/are true when comparing radio telescopes to optical telescopes?

Select all that apply

1. The angular resolution of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light.

2. The large research observations on Mauna Kea use giant reflecting telescopes.

3. Spectrographs separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties.

4. The twin 10-m Keck telescopes can work together to obtain better angular resolution through a technique known as interferometry.

5. The Chandra X-ray observatory focuses X-rays with grazing incidence mirrors.

6. A 10-meter telescope has a larger light-collecting area than a 4-meter telescope

7. Galileo's telescope designs using lenses were examples of refracting telescopes.

1. At these wavelengths, it is necessary to build telescopes with vast light-collecting areas to obtain maps of sufficient sensitivity to faint cosmic signals.

2. At these wavelengths, it is necessary to build telescopes with very large signal-sensing baselines to obtain maps of sufficient detail.

3. Radio astronomers have pioneered the use of multiple telescopes working in concert that can produce maps of radio emission as detailed as optical images. Those arrays of multiple telescopes are known as interferometers.

4. Astronomical observations at these wavelengths can be obtained even during storms.

The value of X-ray and gamma-ray astronomy is based on the fact that some of the most energetic sources in the cosmos radiate at these wavelengths. Magnetic storms in stellar atmospheres (including storms on the Sun), exploding stars and their nebular remnants, the regions surrounding neutron stars and black holes, and the innermost regions associated with active galactic nuclei characterize the highest energy, shortest wavelength regime. What would you need to obtain a successful X-ray image of a high-energy source?

These two photos were taken at the same time and same location near San Jose, California. The one on the left was taken using visible light. Considering the properties of the other parts of the electromagnetic spectrum, which type of radiation do you think was able to penetrate the dust and smog to obtain the image on the right?

The thickest lenses deflect and bend light

The main reason that most professional research telescopes are reflectors is that

If telescope mirrors could be made of odd sizes, the one with the most light-gathering power would be

The image shown in Figure 5.12 in the textbook ("Resolution") is sharpest when the ratio of wavelength to telescope size is

1. The speed of light is the fastest possible speed, but it still takes time for light to get to its destination.

2. This is not usually noticeable effect over short distances here on the Earth, but as objects get farther away, the "lag time" for information becomes more significant.

3. We see objects not as they are when the light arrives at our eyes, but rather we see them as they were when the light we see left.

4. For farther objects, this "lookback time" becomes greater.

5. Since extremely distant objects will also look incredibly faint to us, we need very large telescopes which can gather and focus enough light to observe such objects.

Explain two reasons why astronomers are continually building larger and larger telescopes.

The primary reason professional observatories are built on the highest mountaintops is to

Compared with radio telescopes, optical telescopes can

When multiple radio telescopes are used for interferometry, resolving power is most improved by increasing

The Spitzer Space Telescope (SST) is stationed far from Earth because

The best frequency range in which to study the hot (million-kelvin) gas found among the galaxies in the Virgo galaxy cluster would be in the following region of the electromagnetic spectrum:

The best way to study warm (1000 K) young stars forming behind an interstellar dust cloud would be to use

blue light.

X-rays.

ultraviolet light.

infrared light.