Chapter 6

Interferometry uses two or more telescopes to achieve

An angular resolution equivalent to that of a much larger telescope

How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?

Four times

What is meant by spectral resolution?

It is measured of how close two spectral lines can be distinguished

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

It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion

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

They are always displayed in false color

What causes stars to twinkle?

bending of light rays by turbulent layers in the atmosphere

The Hubble Telescope obtains higher resolution images than most ground based telescopes because it is?

Above Earth's atmosphere

Which technology can allow a single ground based telescope to achieve images as sharp as those from the Hubble Space Telescope?

Adaptive optics

The diffraction limit is a limit on a telescopes?

Angular resolution

Where should you put a telescope designed for ultraviolet observations?

In Earth's orbit

The largest effective telescope, created by radio interferometry, is the size of

Earth

Which of the following is a principal advantage of CCDs over photographic film?

CCDs capture a much higher percentage of the incoming photons than does film

Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.

Extreme infrared

What does the technique of interferometry allow?

It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.

What do astronomers mean by light pollution?

Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.

The twinkling of stars is caused by?

Motion of air in our atmosphere

To achieve the same angular resolution as a visible light telescope, a radio telescope would need to be?

Much larger

Suppose you look at two stars that are separated in the sky by 0.1 arcsecond using a telescope with an angular resolution of 0.5 arcsecond. What will you see?

One point of light that is the blurred image of both stars

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

Photons of different energy have different wavelengths, some of which are not accessible from Earth's surface and require different collection strategies

In what wavelength range was interferometry first routinely used?

Radio

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

Telescopes collect far more light with far better angular resolution

What does it mean if you see the color red in an image from the Chandra X-ray telescope?

The colors are chosen to represent something about the x-rays recorded by the telescopes

Which of the following statements about light focusing is not true?

The focal plane of a reflecting telescope is always located within a few inches of the primary mirror

Which of the following could not be determined by an observation that uses only spectroscopy?

The size of a distant galaxy

Which of the following is not a good reason to place observatories on remote mountain tops?

To be able to observe at radio wavelengths

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

Ultraviolet and X-rays

What is an artificial star?

a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations

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

What is the purpose of adaptive optics?

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