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