Upper Level ISEE Reading Practice Test 65

1 The idea of black holes was developed
2 by Karl Schwarzschild in 1916. Since then,
3 many different scientists have added to the
4 theory of black holes in space. A black hole
5 is usually defined as a very dense celestial
6 body from which nothing, not even light,
7 can escape. But from what do black holes
8 originate?
9 A black hole begins as a star. A star
10 burns hydrogen, and this process, called
11 fusion, releases energy. The energy released
12 outward works against the star's own
13 gravity pulling inward and prevents the star
14 from collapsing. After millions of years
15 of burning hydrogen, the star eventually
16 runs out of fuel. At this point, the star's
17 own gravity and weight cause it to start
18 contracting.
19 If the star is small and not very heavy,
20 it will shrink just a little and become a white
21 dwarf when it runs out of fuel. White dwarf
22 stars do not emit much energy, so they are
23 usually not visible without a telescope.
24 If the star is bigger and heavier, it will
25 collapse very quickly in an implosion. If the
26 matter that remains is not much heavier than
27 our Sun, it will eventually become a very
28 dense neutron star. However, if the matter
29 that remains is more than 1.7 times the
30 mass of our Sun, there will not be enough
31 outward pressure to resist the force of
32 gravity, and the collapse will continue. The
33 result is a black hole.
34 The black hole will have a boundary
35 around it called the horizon. Light and
36 matter can pass over this boundary to enter,
37 but they cannot pass back out again—this is
38 why the hole appears black. The gravity and
39 density of the black hole prevent anything
40 from escaping.
41 Scientists are still adding to the black
42 hole theory. They think they may have
43 found black holes in several different
44 galaxies, and as they learn more about them,
45 scientists will be able to understand more
46 about how black holes are formed and what
47 happens as the holes change.

1. The purpose of the question in the first paragraph is to

• A. illustrate how little we know about black holes
• B. indicate the source of the facts quoted in the passage
• C. interest the reader in the topic of the passage
• D. set a goal for independent research

2. According to the passage, which of the following causes a collapsing star to become a neutron star?

• A. Mass greater than 1.7 times that of our Sun
• B. Mass less than 1.7 times that of our Sun
• C. Remaining fuel that can be used in fusion
• D. Slow, brief shrinkage process

3. The passage suggests that if we were to send a satellite to the horizon of a black hole, it would probably

• A. begin spinning uncontrollably and fly apart
• B. be immediately repelled from the black hole
• C. be pulled into the black hole and not come back out
• D. enter, and then immediately exit, the black hole

4. According to the passage, which of the following is an effect of the process of fusion?

• A. The star does not immediately collapse.
• B. The star generates hydrogen.
• C. The star survives millions of years longer than average.
• D. The white dwarf fails to produce light.

5. Black holes appear black because

• A. only a little energy escapes them
• B. only one galaxy contains them
• C. they are extraordinarily large
• D. they do not eject light they have absorbed

6. Which of the following best describes the organization of the passage?

• A. It discusses the biggest, heaviest celestial bodies before moving on to the smaller, lighter ones.
• B. It introduces the topic and then narrates chronologically the process by which stars become black holes.
• C. It uses a personal story to introduce the topic, and then compares and contrasts black holes.
• D. It uses the example of one specific black hole in order to generalize.