PUZZLE

Stars may be spheres, but not every celestial object is spherical. Objects in the

universe show a variety of shapes: round planets (some with rings), tailed comets,

wispy cosmic gas and dust clouds, ringed nebulae, pinwheel-shaped spiral galaxies,

and so on. But none of the shapes on this list describes the largest single entities in the

(5)      universe. These are the double radio sources, galaxies with huge clouds of radio emission

that dwarf the visible galaxies, sometimes by a factor of a hundred or more. Stretching

over distances greater than a million light-years, these radio-emitting regions resemble

twin turbulent gas clouds, typically forming dumbbell-like shapes with the visible

galaxy (when it is visible) in the center.

 

(10)              These double radio sources present astronomers with a puzzle. Their radio emission

arises from the synchrotron process, in which electrons accelerated to nearly the speed

of light move through magnetic fields. However, in view of the rate at which the radio

sources emit energy, they should disappear in a few million years as their electrons slow

down and cease producing radiation. Somehow new electrons must be continually

(15)    accelerated to nearly the speed of light, otherwise, by now almost none of the double

radio sources would be observed.

 

With the advent of high-resolution radio interferometers during the late 1970′s, part

of the answer became clear: the electrons are produced in jets that are shot out in

opposite directions from the center of galaxy. Remarkably narrow and highly directional,

(20)    the jets move outward at speeds close to the speed of light. When the jets strike the

highly rarefied gas that permcales intergalactic space, the fast-moving electrons lose

their highly directional motion and form vast clouds of radio-emitting gas.

 

Cosmic jets have ranked among the hottest topics of astronomical research in recent

years as astronomers strive to understand where they come from. Why should a galaxy

(25)    eject matter at such tremendous speeds in two narrow jets? And why are such jets not

seen in the Milky Way?

 

Reading Comprehension 78

Question 1

The word “celestial” in line 1 could best be replaced by

  astronomical
  scientific
  glowing
  visible
Question 2

The word “entities” in line 4 is closest in meaning to

  processes
  factors
  puzzles
  objects
Question 3

In the first paragraph, the author describes objects in the universe in terms of their

  color
  location
  shape
  origin
Question 4

According to the passage, scientists do not fully understand why double radio sources

  cannot be observed with a telescope
  are beginning to slow down
  are not as big as some planets and stars
  have not eventually disappeared
Question 5

The word “their” in line 22 refers to

  clouds
  electrons
  directions
  speeds
Question 6

According to the passage, what happens when electrons and gas collide in space?

  The electrons disperse
  The electrons become negatively charged
  The gas becomes less radiated
  The gas becomes more condensed
Question 7

The author suggests that astronomers consider the study of cosmic jets to be

  an intriguing challenge
  a subjective debate
  an obsolete scientific field
  an unprofitable venture
Question 8

In what lines does the passage compare the size of double radio sources with that of other galaxies?

  Lines 12-14
  Lines 19-20
  Lines 4-6
  Lines 23-24
Question 9

Where in the passage does the author mention a technology that aided in the understanding of double radio sources?

  Line 21
  Line 2
  Line 7
  Line 17
Question 10

The paragraph following the passage most likely discusses

  possible reasons for the presence of cosmic jets
  the discovery of the first double radio sources.
  an explanation of the synchrotron process
  specific double radio sources
Once you are finished, click the button below. Any items you have not completed will be marked incorrect.Get Results

There are 10 questions to complete.

By muhibfunkyou

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s