Question 1

Which statement about the twinkling of stars and planets is NOT correct?

Accepted Answer

The statement "The twinkling of stars is an inherent phenomenon and cannot be reduced by any observing technique" is not correct because observing techniques such as adaptive optics can be used to reduce the effects of twinkling.

Question 2

What characteristic of the 10-m Keck telescope makes it fundamentally different from older telescopes,such as the one on Mt.Palomar?

Accepted Answer

The Keck telescope's primary mirror is made up of 36 separate mirror segments, which allows for greater flexibility in adjusting and compensating for distortions in the incoming light. This is a major technological advance from older telescopes, such as the one on Mt. Palomar, which typically had a single, solid primary mirror.

Question 3

The detector that in many instances has replaced the photographic plate for astronomical photography is the:

Accepted Answer

CCDs have largely replaced photographic plates as detectors for astronomical photography due to their superior sensitivity, linearity, and ability to record digital data. Photomultiplier tubes and image-intensifier tubes are also used in some applications, but CCDs are more commonly used. Diffraction gratings and interferometers are not detectors, but rather instruments used for analyzing light.

Question 4

What factor has seriously reduced the effectiveness over the last few years of the 5-m Hale telescope on Mt.Palomar,California,formerly the largest telescope in the world?

Accepted Answer

Light pollution from nearby cities has seriously reduced the effectiveness of the 5-m Hale telescope on Mt. Palomar, as it interferes with the telescope's ability to observe faint astronomical objects.

Question 5

What is the angular resolution of the Hubble Space Telescope?

Accepted Answer

The answer of What is the angular resolution of the...

Question 6

Which of the following techniques is the key factor in a telescope that uses adaptive optics to correct for atmospheric distortion of images,or "seeing"?

Accepted Answer

Adaptive optics corrects for atmospheric distortion by adjusting the shape and position of a small mirror within the telescope optics many times per second. Computer-controlled motors are used to make these adjustments. The other options do not describe adaptive optics.

Question 7

Images from the 5-meter telescope at Mt.Palomar are NOT as clear as they were when the telescope was first put into operation over 60 years ago.Why is this?

Accepted Answer

Light pollution has increased significantly over the past 60 years, affecting the clarity of astronomical images from ground-based telescopes like the one at Mt. Palomar.

Question 8

The sharpest images of stars that can be formed by a single,large,ground-based,visible-light telescope are of the order of what angular size?

Accepted Answer

The sharpest images of stars that can be formed by a single, large, ground-based, visible-light telescope are of the order of 0.2 arc second, which is option D. This is due to atmospheric turbulence, which blurs the images of stars seen from the ground.

Question 9

What does the word seeing mean to an astronomer using a telescope?

Accepted Answer

Seeing refers to the twinkling and blurring of the image due to turbulence in Earth's atmosphere. This affects the sharpness and clarity of the image seen through the telescope.

Question 10

The Hubble space Telescope is NOT designed to investigate:

Accepted Answer

The Hubble space telescope is not designed to investigate radio waves.

Question 11

How much more efficient at collecting incoming photons is the modern charge-coupled device (CCD)compared with a typical photographic plate?

Accepted Answer

The answer of How much more efficient at collecting incoming...

Question 12

If one observatory site is described as having better "seeing" than another observatory site,what is it that is BETTER at the first site?

Accepted Answer

"Seeing" refers to the extent to which atmospheric turbulence causes variations in the light passing through the atmosphere, thus causing distortion or blurring of images. So, if one observatory site is described as having better "seeing" than another observatory site, it means that the air turbulence is less at that site, causing less twinkling and blurring of the images. A, B, and D are not directly related to the term "seeing".

Question 13

It is difficult to improve the angular resolution of optical telescopes located on the surface of Earth beyond a certain limit because:

Accepted Answer

The distortion caused by air turbulence, commonly known as "seeing," limits the angular resolution of telescopes on Earth more than the telescope optics. This is why many modern telescopes are located in space or in high-altitude locations to reduce the effects of atmospheric distortion.

Question 14

After the Hubble Space Telescope was launched,it was found to suffer seriously from:

Accepted Answer

The Hubble Space Telescope suffered from spherical aberration, which means that the light rays that entered the telescope did not all focus at the same point, causing blurry and distorted images. This was due to a flaw in the primary mirror's construction, which was eventually corrected during a servicing mission in 1993.

Question 15

The BEST Earth-based sites for modern large astronomical telescopes,which provide the least seeing effects on astronomical images,are:

Accepted Answer

The best choice is on the tops of high mountains, above a large fraction of the disturbing atmosphere. This is because being at a high altitude allows telescopes to be above much of the Earth's atmosphere, which causes turbulence and blurs astronomical images. This significantly reduces the impact of seeing effects on astronomical images, providing clearer and more stable images.

Question 16

One way to distinguish stars from planets,particularly when they appear near the horizon,is that stars appear to twinkle and planets shine steadily.Which of the following statements is a reasonable explanation for this phenomenon?

Accepted Answer

The disk of a planet appears larger than the disk of a star when observed from Earth, allowing for a central part of the planet's disk to shine steadily and not appear to twinkle. Stars are point sources of light and any refraction through moving air in Earth's atmosphere causes their light to appear to flicker bright and dim. The brightness of the light from planets compared to stars has no impact on this phenomenon. Planets reflecting light, rather than emitting it, also has no impact on the refraction and the twinkling of stars.

Question 17

Twinkling is an observational problem when making observations from:

Accepted Answer

Twinkling is caused by atmospheric turbulence affecting ground-based telescopes. Active optics can help correct for some distortions, but twinkling is still an issue.

Question 18

The Hubble Space Telescope,placed in orbit by the space shuttle in 1990,has a primary mirror of diameter:

Accepted Answer

The Hubble Space Telescope has a primary mirror with a diameter of 2.4 meters.

Question 19

The primary mirror in the 10-m Keck telescope consists of:

Accepted Answer

The primary mirror of the Keck telescope is composed of 36 hexagonal segments that work together as a single mirror, each segment being precisely controlled to maintain the correct shape and focus.

Question 20

The major cause of blurred and unsharp images of objects observed through very large telescopes at the extreme limit of magnification is the:

Accepted Answer

Air turbulence in Earth's atmosphere, also known as atmospheric seeing, causes distortions in the light passing through it, which can result in blurry and unsharp images observed by telescopes. This is why many observatories are built at high altitudes or in locations with very stable atmospheric conditions to minimize the effects of atmospheric seeing.

Quiz 3: Light and Telescopes