Directions: Read the given passage carefully and answer the questions as follows:
Passage
Supernovas are among the most energetic events in the universe and result in the complete disruption of stars at the end of their lives. Originally, the distinction between Type I and Type II supernovas was based solely on the presence or absence of hydrogen atoms (hydrogen lines). Supernovas without hydrogen lines were called Type I, while those with hydrogen lines were Type II. Subsequent analysis of many of these events revealed that this empirical classification schema instead reflected two different mechanisms for the supernova explosion.
Type I supernovas happen in binary stars — two stars that orbit closely each other — when one of the two binary stars is a small, dense, white dwarf star. If the companion star ranges too close to the white dwarf that it is orbiting, the white dwarf’s gravitational pull will draw matter from the other star. When the white dwarf acquires enough matter to become at least 1.4 times as big as the Sun, it collapses and explodes in a supernova.
Type II supernovas occur when a star, much more massive than the Sun, ends its life. When such a star begins burning out, the core of the star quickly collapses releasing amazing energy in the form of neutrinos, a kind of particle smaller than even an atom. Electromagnetic radiation — energy that is electric and magnetic — causes the star to explode in a supernova. Whereas Type I supernovas typically destroy their parent stars, Type II explosions usually leave behind the stellar core.
The classification schema regarding the mechanism for supernova explosions helps to more succinctly answer the question: Is the Sun in danger of becoming a supernova? Neither does our Sun have a companion star orbiting it nor does our Sun have the mass necessary to become a supernova. Furthermore, it will be another billion years until the Sun runs out of fuel and swells into a red giant star before going into a white dwarf form.
Question for Practice Test: Reading Comprehension - 48
Try yourself:It can be inferred from the passage that
Explanation
Snapshot: This question highlights the need to avoid choosing “reversed cause-and-effect relationships” and “fabricated cause-and-effect relationships” which are the hallmarks of certain incorrect inference answer choices that appear difficult Reading Comprehension passages.
Choices B, C, and D represent examples of such reversed cause-and-effect relationships. In choice B, it is the dense white dwarf that explodes as a supernova, not the companion star! Choice C suggests that a star such as the Sun must first become a white dwarf before becoming a red giant. This stands in opposition to what is suggested in the last line of the passage: that a star such as the Sun “swells into a red giant star before going into white dwarf form.” Choice D is more subtle. We know that Type II supernovas release energy from neutrinos and electromagnetic radiation. However the cause-and-effect relationship is reversed. It is the collapsing of the star that causes the release of energy as neutrinos and electromagnetic radiation, subsequent to the exploding of the star as a supernova. Choice D suggests that the energy and electromagnetic radiation is what causes the star to collapse and explode.
Choice A is readily inferable from the second and third sentences of the opening paragraph. Classifying Type 1 and Type 2 events based on the presence or absence of hydrogen or based on the different explosion mechanisms are not necessarily incompatible with one another. In other words, an event might be classified as a Type I supernova because it doesn’t have hydrogen lines or because it explodes as a result of being a white dwarf that acquires matter from its orbiting binary star. An event might be classified as a Type II supernova because it does have hydrogen lines or because it explodes as a result of being a massive collapsing star.
There is no indication from the information given in the passage that supernovas are rare events in the universe at large (choice E). For all we know, they are common in some galaxies and rare in others. It is important not to draw upon outside knowledge when answering Reading Comprehension questions.
Author’s note: Per choice D, a simple example might serve to better clarify the nature of the potential overlap. Schema 1: Say, for example, we classify a good day versus a bad day by the absence or presence of rain. A good day will have the absence of rain while a bad day will have the presence of rain. Schema 2: We might also classify a good day versus a bad day based on the number of hours of sunshine received. A good day will have a substantial number of hours of sunshine while a bad day will have a minimum number of hours of sunshine. In short, between schemas 1 and 2, a good day might have the absence of rain and a substantial number of hours of sunshine. A bad day might have the presence of rain and a minimal number of hours of sunshine. As we can quickly see, a good day might be classified as a “good day” under either schema. On the contrary, a day might have a little rain and also a substantial number of hours of sunshine. In this case, it is considered a bad day under schema 1 but a good day under schema 2. Likewise, a day might have no rain and a minimal number of hours of sunshine. In this case, it is considered a good day under schema 1 but a bad day under schema 2. Here, there is no overlap between the two schemas.
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Question for Practice Test: Reading Comprehension - 48
Try yourself:How is this passage organized?
Explanation
Snapshot: Science passages typically exist to describe (as opposed to Social Science passages which typically exist to argue) and such passages frequently incorporate two theories, hypotheses, or explanations.
The new schema is based on the distinction between Type I and Type II supernovas; the original schema is one based on the absence of hydrogen (Type I) or the presence of hydrogen (Type II). The example of the Sun is provided as support for how the classification system works. Choice D best summarizes this structure.
In choice A, the schemas do not necessarily overlap. An event classified as a Type I supernova under one schema might not be classified as a Type I supernova under the other schema (and vice versa). Also, the two schemas are described but not contrasted with each other. In choice B, it is inaccurate to describe the original theory as being overturned. The new theory is very much an “extension” of the old theory rather than a “replacement.” In choice C, no conclusion is offered. For example, the author does not state that Type I is “better or worse” than Type II, or that Type I is easier to use in describing or explaining the occurrence of supernovas than Type II. No reconciliation between the two different classification systems is provided per choice E. The two different systems are very much distinct and do not lend themselves to reconciliation.
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Question for Practice Test: Reading Comprehension - 48
Try yourself:According to the passage, which statement or statements below are true?
I. The energy created from a Type II explosion is greater than the energy created by a Type I explosion.
II. The sun is not a binary star.
III. Both Type I and Type II supernovas result in the complete destruction of the exploding star.
Explanation
Snapshot: This question introduces the Roman numeral question-type in Reading Comprehension.
The statement represented by statement I cannot be proved or disproved from information gleamed from the passage. Although Type II stars appear bigger than Type I (“much more massive than the Sun” versus “at least 1.4 times as big as the Sun”), it is not certain which Type releases the greatest amount of overall energy.Statement II is true. To be a binary star, the Sun must have an orbiting partner. Because the Sun does not, it does not qualify as a binary star (see first sentence of second paragraph as well as the last paragraph).Statement III is false. The last line of the third paragraph clearly states: “Whereas Type I supernovas typically destroy their parent stars, Type II explosions usually leave behind the stellar core.” Type II supernovas, therefore, do not result in “complete destruction of the exploding star.”Author’s note: This passage did not contain an overview question. Nonetheless, it is always recommended to do a T-S-P drill, asking what is the topic, scope, and purpose of the passage. The topic is “supernovas.” The scope is “Type I and Type II supernovas.” The purpose is “to describe a new schema for classifying Type I and Type II supernovas.”
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Question for Practice Test: Reading Comprehension - 48
Try yourself:Which of the following best summarizes the author’s answer to the question: Is the Sun in danger of becoming a supernova?
Explanation
Snapshot: This question links two parts of the passage, namely the last paragraph with paragraphs two and three.
Answer choice C describes accurately and completely the author’s view in the final paragraph. The Sun is not a binary star because it doesn’t have companion star orbiting it, so it can’t qualify as a Type I supernova. Nor does the Sun have the size necessary to become a Type II supernova (it would have to be at least 1.4 times its own size).
In choice A, there is no relationship suggested between the size of the Sun and its ability to have a white dwarf partner (per Type I). Choices B and D create unwarranted linkages between Type I and Type II supernovas. It is the white dwarf, not the Sun, which would undergo collapse and explosion as a supernova. In choice E, even if the Sun does become a red giant before becoming a white dwarf, it does not mean that it will become a supernova. It would still need another star (i.e., binary star) which it could absorb en route to becoming a Type I supernova.
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