Question 1

Why is an image recorded with a CCD better for astronomers than an image recorded on photographic film or plates?

Accepted Answer

CCD's are more efficient in recording light, allowing more accurate measurements of brightness and have digital output that is easier to transfer and analyze on a computer. Therefore, all of the above options are correct.

Question 2

An astronomer who is observing visible light from a glowing cloud of gas in space uses an instrument which contains a grating with thousands of grooves on its surface. What will this instrument allow our astronomer to do?

Accepted Answer

A grating with thousands of grooves on its surface is a type of diffraction grating, which can separate light into its component colors (spectrum). Therefore, this instrument will allow the astronomer to spread out the light from the cloud into a spectrum, which can be used to determine the chemical composition, temperature, and other properties of the gas.

Question 3

When an astronomer involved in a research project says he is going to look at the observatory's plate collection, what will he be looking at?

Accepted Answer

The astronomer is likely going to look at a collection of glass plates with light-sensitive chemicals on them, on which the appearance of the sky was recorded. This is a common technique used in observational astronomy before digital imaging became widely available. The images on the plates can be analyzed and used to study the properties of stars, galaxies, and other celestial objects.

Question 4

The two regions of the electromagnetic spectrum where the Earth's atmosphere is transparent (radiation can get in) are visible light and:

Accepted Answer

While there are certain wavelengths within the ultraviolet and infrared regions that can penetrate the Earth's atmosphere, the majority of these wavelengths are absorbed or scattered by the atmosphere. However, certain radio waves are able to penetrate the Earth's atmosphere and are therefore transparent.

Question 5

Radio telescopes of modest size can't make out as much detail (have a lower resolution) than visible light telescopes. How do astronomers overcome this limitation?

Accepted Answer

By connecting several radio telescopes together electronically, astronomers can increase the size of their "virtual telescope" and achieve higher resolution. This technique is known as interferometry. Option A is not practical as it would be extremely expensive and difficult to build. Option B is incorrect as interferometry does allow for higher resolution. Option D is partially true, but it is not practical to launch numerous small radio telescopes into orbit. Option E is not a practical solution as the engineers responsible for the Hubble Space Telescope are not necessarily specialized in radio telescope technology.

Question 6

To break up light into the component colors that it contains, astronomers use a device called:

Accepted Answer

Spectrometers are instruments used to break up light into its component colors, allowing astronomers to study the spectrum and learn about the physical properties of the object emitting the light. Telescopes, CCDs, Cassegrain splitters, and interferometer arrays are all useful tools but not specifically designed to break up light into its colors.

Question 7

The first radio telescope was built in the 1930's by

Accepted Answer

The first radio telescope was built in the 1930's by Karl Jansky, an American physicist and radio engineer, who was studying the sources of static interference in transatlantic radio communications. He discovered that the interference was coming from radio waves originating from the Milky Way, and built a radio telescope to study them.

Question 8

The SOFIA Project is

Accepted Answer

The SOFIA (Stratospheric Observatory for Infrared Astronomy) Project is an airplane with a 2.5-meter infra-red telescope on board that is designed to fly above much of the water vapor in the Earth's atmosphere, allowing it to capture clearer images of celestial objects in the infrared spectrum.

Question 9

In the summer of 1996, the European Space Agency announced that it would be suspending the operations of the International Ultraviolet Explorer. Astronomers who were most unhappy about that announcements were likely to be studying what types of objects?

Accepted Answer

The International Ultraviolet Explorer was primarily used to study very hot stars, so astronomers studying these objects would have been most impacted by its suspension of operations.

Question 10

What type of telescope can be used routinely on the surface of the Earth during the DAY?

Accepted Answer

A radio telescope can be used during the day because radio waves are not affected by daylight and can pass through the atmosphere. Other types of telescopes, such as visible-light and x-ray telescopes, are greatly hindered by the presence of daylight and the scattering of light in the atmosphere, making them impractical for daytime use.

Question 11

Our textbook discusses that radio astronomers are building more and more arrays of radio telescopes, where many "dishes" are connected together. What advantage do such arrays have?

Accepted Answer

Arrays of radio telescopes provide higher resolution than individual dishes because they can combine signals from multiple dishes, resulting in better image clarity and detail. Option A is incorrect because radio telescopes still cannot see through the Earth's atmosphere even with an array. Option B is incorrect because both individual dishes and arrays can split radio waves into a spectrum. Option D is incorrect because both individual dishes and arrays can be built on tall mountains or flat ground alike.

Question 12

Which of the following is NOT a detector of radiation from space that astronomers have used?

Accepted Answer

Refracting telescopes are not detectors of radiation from space, but rather instruments used to visually observe celestial objects. The other choices are all types of detectors that astronomers have used to study radiation from space.

Question 13

Which of the following major telescopes was not located in space?

Accepted Answer

The Keck Telescope is a ground-based observatory located in Mauna Kea, Hawaii. The other options listed are all telescopes located in space.

Question 14

Which of the following types of telescopes can be used ONLY above the Earth's atmosphere?

Accepted Answer

X-ray telescopes can only be used above the Earth's atmosphere because X-rays are absorbed by the atmosphere and cannot penetrate it to be detected on the ground.

Question 15

You are an astronomer who wants to study a faint star in the process of being born, which gives off most of its faint radiation in the infra-red. Which of the following would NOT be a step you would want to take?

Accepted Answer

Heating your telescope would not be beneficial for observing faint infrared radiation from a star being born. Infrared observations require minimizing thermal emissions from the telescope itself, which would be increased by heating it.

Question 16

When astronomers do radar astronomy, they

Accepted Answer

Radar astronomy involves bouncing a radar beam off the surface of solid objects in our solar system, such as planets, asteroids, and moons, to gather information about their composition, shape, and surface features. It is used to create detailed maps of these objects and study their physical properties. The other choices are not accurate descriptions of radar astronomy.

Question 17

What was the major problem with the Hubble Space Telescope when it was first launched into orbit?

Accepted Answer

The major problem with the Hubble Space Telescope when it was first launched into orbit was that its mirror's shape was slightly wrong, causing all the light to not come to a single focus. This resulted in blurry images and compromised the performance of the telescope.

Question 18

In a radio telescope, the role that the mirror plays in visible-light telescopes is played by:

Accepted Answer

In a radio telescope, the role that the mirror plays in visible-light telescopes is played by a large metal dish (antenna). The metal dish collects the radio waves and reflects them onto a receiver, which detects and analyzes the signal.

Question 19

Of the following, which has the highest resolution (ability to make out fine detail):

Accepted Answer

The Very Long Baseline Array (VLBA) of Radio Telescopes has the highest resolution among the options listed because it uses a technique called Very Long Baseline Interferometry (VLBI), which combines observations from telescopes spread across vast distances, effectively creating a telescope with a diameter as large as the separation between the facilities. This allows for extremely high resolution, far surpassing that of a single dish, regardless of its size.

Question 20

Which of the following is NOT an advantage that the Hubble Space Telescope has over large telescopes on Earth?

Accepted Answer

The Hubble does not have a larger aperture than any visible-light telescope on Earth. There are ground telescopes, such as the Keck Observatory in Hawaii, that have larger apertures.

Quiz 6: Astronomical Instruments