Astronomy study guide Chapter 6

Characteristics of Reflecting Telescopes and an example of one

The Hubble Space Telescope Most commonly used by professional astronomers today world's largest telescope

what is the angular resolution of the human eye?

about 1 arcminute, or 1/60 of a degree

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

above Earth's atmosphere

Suppose astronomers built a 110-meter telescope. How much greater would its light-collecting area be than that of the 10-meter Keck telescope?

120

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

4

Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?

A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.

Visible light reaches what altitude

Earth's surface

Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?

High spectral resolution

What do we mean by the diffraction limit of a telescope?

It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images

Which of the following best describes what we mean by the focal plane of a telescope?

It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope

What do astronomers mean by light pollution?

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

In what wavelength range was interferometry first routinely used?

Radio

What types of light reach Earth's surface?

Radio waves and Visible Light

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

Telescopes can collect far more light with far better angular resolution. Telescopes have a larger light-collecting area than the eye and better(smaller) angular resolution

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?

The two stars will look like a single point of light

Which of the following is always true about images captured with X-ray telescopes?

They are always shown with colors that are not the true colors of the objects that were photographed

X rays from astronomical objects can only be detected from telescopes in space. (T/F)

True

most astronomical objects emit light over a broad range of wavelengths (T/F)

True

What type of light has the highest altitude?

X-rays

Which of the following wavelength regions cannot be studied with telescopes on the ground?

X-rays and Ultraviolet

What is the order of the types of light that are from the highest to lowest(earth's surface)?

X-rays, most ultraviolet light, most infrared light, (Visible light = Radio waves)

If our eyes were sensitive only to X-rays, the world would appear

dark because X-ray light does not reach Earth's surface

A radio telescope and an optical telescope of the same size have the same angular resolution (T/F)

false

Where should you put a telescope designed for ultraviolet observations?

in earth orbit

If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?

in space

What is the purpose of interferometry?

it allows two or more small telescopes to achieve the angular resolution of a much larger telescope

What is a CCD?

it is an electronic detector that can be used in place of photographic film for making images

Suppose the two stars are separated in the sky by .1 arcsecond. If you look at them with a telescope that has an angular resolution of .5 arcsecond, what will you see?

one point of light

At which wavelength range is there no current or planned space observatory?

radio

Which of the following wavelength regions can be studied with telescopes on the ground?

radio, visible and very limited portions of the infrared and ultraviolet regions other parts of the electromagnetic spectrum require telescopes in space

What is the purpose of adaptive optics?

reduces blurring caused by atmospheric turbulence for telescopes on the ground and it does this by changing the shape of a telescope mirror to compensate for the way that the atmosphere causes the light from a star to move around

What does angular resolution measure?

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

Which of the following could not be measured by an observation that uses only imaging?

the rate at which a variable star brightens and dims

three main categories of observation generally used by astronomers

timing to track how an object's brightness varies with time spectroscopy to spread an object's light into a spectrum imaging to get a picture of an astronomical objects

What is the purpose of adaptive optics?

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

Which of the following effects is caused by atmospheric turbulence?

twinkling of stars, twinkling is not happening earth's atmosphere

Characteristics of Refracting Telescopes and an example of one

very large telescopes become "top-heavy" incoming light passes through glass the world largest is 1-meter in diameter Galileo's telescopes