TF阅读真题第807篇The Birth of the Solar System

The Birth of the Solar System

The Birth of the Solar System

 

 

 

Scientists believe that the sun and the planets in our solar system formed from a vast cloud of dust and gas called the solar nebula. Important evidence for this view comes from meteorites like the one called Allende (named for the village near where it was found), which contains tiny beads of magnesium-silicate minerals called chondrules, set in a matrix composed of a wide variety of tiny mineral grains and organic compounds. Embedded in this matrix are other strange objects. Among them are white inclusions (foreign bodies enclosed in a mineral or rock) composed mainly of oxides of aluminum and calcium known as calcium-aluminum inclusions (CAIs). The CAIs solidified at a very high temperature and thus must have been the very first solid objects to have formed in the solar nebula, when it was still very hot. The ages of several CAIs have been determined by radiometric dating, a technique by which age is determined from the content of radioactive elements and their decay products. Radiometric dating established that the chondrules are 4.566 billion years old, making them the oldest known objects in the solar system.

Allende is important for other reasons. First, it and other carbonaceous chondrites have a composition similar (except for hydrogen, helium, and other gaseous elements) to that of the Sun’s visible outer layer, and for this reason they may be the best available representatives of the bulk composition of the solar nebula. This match in composition is what allows us to use carbonaceous chondrites to deduce what happened in the early solar system. Second, Allende contains a few hardy particles that survived the events leading up to the formation of the solar nebula. They include particles, typically only a few millionths to a few thousandths of a millimeter across, of diamond, silicon carbide, graphite, and corundum (aluminum oxide). The ratios of the different forms of carbon and of other elements in these grains are much different from the ratios found in anything formed in the solar system. This is why the particles are believed to be relics of old stars that existed before the birth of the solar system.

As the solar nebula cooled, magnesium-iron minerals—the common stuff of Earth—began to form. Most of this material condensed relatively close to the “protosun” (the dense core of matter that formed at the center of the solar nebula) in the region now occupied by Mercury, Venus, Earth, and Mars. Together, these are known as the rocky, or terrestrial, planets precisely because they are made of rocks composed of silicates. More distant from the Sun, temperatures were low enough for elements to freeze, so that Jupiter, Saturn, Uranus and Neptune—the so-called gas-rich giants of that part of the solar system—as well as Pluto, would end up consisting of higher proportions of these ices. This is getting ahead of the story, however. During the early stage when the solar nebula was cooling, in the region of the future terrestrial planets, small particles formed progressively larger aggregates as they collided with one another, and larger bodies swept up more material and thus grew more rapidly than smaller bodies. The result of this process was many billions of “planetesimals,” or solid bodies each 1 kilometer (0.62 mile) or so across, rotating around the protosun.

At some point after the formation of planetesimals, the seminal event of the solar system occurred: the Sun ignited to become a star. As dust collapsed in the center of the solar nebula, the gravitational pressure there became high enough to cause a nuclear process known as fusion, in which hydrogen is converted into helium atoms and, in doing so, releases energy. The ignition swept away what gas and small particles remained in the inner solar system, leaving only bodies too large to be affected—the planetesimals. The timing is one of the numerous accidents that led to our existence. Had the Sun ignited before the formation of the planetesimals, all matter in the solar system would have been swept away, and there would have been no Earth or rocky planets!

1

Scientists believe that the sun and the planets in our solar system formed from a vast cloud of dust and gas called the solar nebula. Important evidence for this view comes from meteorites like the one called Allende (named for the village near where it was found), which contains tiny beads of magnesium-silicate minerals called chondrules, set in a matrix composed of a wide variety of tiny mineral grains and organic compounds. Embedded in this matrix are other strange objects. Among them are white inclusions (foreign bodies enclosed in a mineral or rock) composed mainly of oxides of aluminum and calcium known as calcium-aluminum inclusions (CAIs). The CAIs solidified at a very high temperature and thus must have been the very first solid objects to have formed in the solar nebula, when it was still very hot. The ages of several CAIs have been determined by radiometric dating, a technique by which age is determined from the content of radioactive elements and their decay products. Radiometric dating established that the chondrules are 4.566 billion years old, making them the oldest known objects in the solar system.

According to paragraph 1, all of the following are true of the meteorite called Allende EXCEPT

 

Negative Factual Information Questions否定事实信息题

 

AIts matrix contains many different minerals and compounds.

BIt contains large chunks of magnesium-silicate minerals.

CBoth chondrules and CAls are embedded in its matrix.

DIt is named after a village.

2

Scientists believe that the sun and the planets in our solar system formed from a vast cloud of dust and gas called the solar nebula. Important evidence for this view comes from meteorites like the one called Allende (named for the village near where it was found), which contains tiny beads of magnesium-silicate minerals called chondrules, set in a matrix composed of a wide variety of tiny mineral grains and organic compounds. Embedded in this matrix are other strange objects. Among them are white inclusions (foreign bodies enclosed in a mineral or rock) composed mainly of oxides of aluminum and calcium known as calcium-aluminum inclusions (CAIs). The CAIs solidified at a very high temperature and thus must have been the very first solid objects to have formed in the solar nebula, when it was still very hot. The ages of several CAIs have been determined by radiometric dating, a technique by which age is determined from the content of radioactive elements and their decay products. Radiometric dating established that the chondrules are 4.566 billion years old, making them the oldest known objects in the solar system.

According to paragraph 1, why are CAls believed to have been the first solid objects in the solar nebula?

 

Factual Information Questions事实信息题

 

ACAls contain many radioactive elements.

BCAls become solid at very high temperatures, which existed initially in the solar nebula.

CCAls contain more calcium and aluminum, which was common in the oldest objects in the solar nebula

DCAls are unusual in both their color and size

3

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information

 

Sentence Simplification Questions句子简化题

 

ALike other carbonaceous chondrites, Allende has enough hydrogen, helium, and other gases to make it a good representative of the composition of the solar nebula.

BThe Sun’s visible outer layer is the best indicator of the composition of the solar nebula, and carbonaceous chondrites like Allende are also similar in composition.

CCarbonaceous chondrites like Allende are our best indicators of the composition of the solar nebula because of their similarity to the Sun’s outer layer

DBecause they lack gaseous elements, carbonaceous chondrites like Allende are better representatives of the solar nebula than is the Sun’s visible outer layer.

4

Allende is important for other reasons. First, it and other carbonaceous chondrites have a composition similar (except for hydrogen, helium, and other gaseous elements) to that of the Sun’s visible outer layer, and for this reason they may be the best available representatives of the bulk composition of the solar nebula. This match in composition is what allows us to use carbonaceous chondrites to deduce what happened in the early solar system. Second, Allende contains a few hardy particles that survived the events leading up to the formation of the solar nebula. They include particles, typically only a few millionths to a few thousandths of a millimeter across, of diamond, silicon carbide, graphite, and corundum (aluminum oxide). The ratios of the different forms of carbon and of other elements in these grains are much different from the ratios found in anything formed in the solar system. This is why the particles are believed to be relics of old stars that existed before the birth of the solar system.

The word “deduce” in the passage is closest in meaning to

 

Vocabulary Questions词汇题

 

Aillustrate

Binfer

Cdiscuss

Dquestion

5

Allende is important for other reasons. First, it and other carbonaceous chondrites have a composition similar (except for hydrogen, helium, and other gaseous elements) to that of the Sun’s visible outer layer, and for this reason they may be the best available representatives of the bulk composition of the solar nebula. This match in composition is what allows us to use carbonaceous chondrites to deduce what happened in the early solar system. Second, Allende contains a few hardy particles that survived the events leading up to the formation of the solar nebula. They include particles, typically only a few millionths to a few thousandths of a millimeter across, of diamond, silicon carbide, graphite, and corundum (aluminum oxide). The ratios of the different forms of carbon and of other elements in these grains are much different from the ratios found in anything formed in the solar system. This is why the particles are believed to be relics of old stars that existed before the birth of the solar system.

According to paragraph 2, a few of Allende’s particles are believed to have existed before the formation of the solar system because of

 

Factual Information Questions事实信息题

 

Athe size of the particles

Btheir similarity to particles found in stars

Cthe ratios of different elements in the particles

Dthe unusual form of carbon found in the particles

6

As the solar nebula cooled, magnesium-iron minerals—the common stuff of Earth—began to form. Most of this material condensed relatively close to the “protosun” (the dense core of matter that formed at the center of the solar nebula) in the region now occupied by Mercury, Venus, Earth, and Mars. Together, these are known as the rocky, or terrestrial, planets precisely because they are made of rocks composed of silicates. More distant from the Sun, temperatures were low enough for elements to freeze, so that Jupiter, Saturn, Uranus and Neptune—the so-called gas-rich giants of that part of the solar system—as well as Pluto, would end up consisting of higher proportions of these ices. This is getting ahead of the story, however. During the early stage when the solar nebula was cooling, in the region of the future terrestrial planets, small particles formed progressively larger aggregates as they collided with one another, and larger bodies swept up more material and thus grew more rapidly than smaller bodies. The result of this process was many billions of “planetesimals,” or solid bodies each 1 kilometer (0.62 mile) or so across, rotating around the protosun.

According to paragraph 3, what happened as the solar nebula began to cool?

 

Factual Information Questions事实信息题

 

AThe gases closest to the protosun moved farther away from it.

BThe protosun formed outside the solar nebula

CMagnesium-iron minerals formed in the region of today’s terrestrial planets.

DThe gases in the areas now occupied by the terrestrial planets froze.

7

As the solar nebula cooled, magnesium-iron minerals—the common stuff of Earth—began to form. Most of this material condensed relatively close to the “protosun” (the dense core of matter that formed at the center of the solar nebula) in the region now occupied by Mercury, Venus, Earth, and Mars. Together, these are known as the rocky, or terrestrial, planets precisely because they are made of rocks composed of silicates. More distant from the Sun, temperatures were low enough for elements to freeze, so that Jupiter, Saturn, Uranus and Neptune—the so-called gas-rich giants of that part of the solar system—as well as Pluto, would end up consisting of higher proportions of these ices. This is getting ahead of the story, however. During the early stage when the solar nebula was cooling, in the region of the future terrestrial planets, small particles formed progressively larger aggregates as they collided with one another, and larger bodies swept up more material and thus grew more rapidly than smaller bodies. The result of this process was many billions of “planetesimals,” or solid bodies each 1 kilometer (0.62 mile) or so across, rotating around the protosun.

Which of the following best describes the organization of paragraph 3?

 

Organization Questions组织结构题

 

AAn explanation of why the solar nebula cooled followed by the impact of that process

BA discussion of a later stage of the solar system development followed by a discussion of an early stage of its development

CAn outline of the causes explaining how small particles formed progressively larger aggregates as they collided with one another

DA discussion of two alternative theories explaining the formation of terrestrial planets

8

At some point after the formation of planetesimals, the seminal event of the solar system occurred: the Sun ignited to become a star. As dust collapsed in the center of the solar nebula, the gravitational pressure there became high enough to cause a nuclear process known as fusion, in which hydrogen is converted into helium atoms and, in doing so, releases energy. The ignition swept away what gas and small particles remained in the inner solar system, leaving only bodies too large to be affected—the planetesimals. The timing is one of the numerous accidents that led to our existence. Had the Sun ignited before the formation of the planetesimals, all matter in the solar system would have been swept away, and there would have been no Earth or rocky planets!

What can be inferred from paragraph 4 about the planetesimals?

 

Inference Questions推理题

 

AThey eventually became the rocky planets near the Sun.

BThey were swept farther out into the solar system when the Sun ignited.

CThey formed after the Sun became a star.

DThey broke up into small particles when the Sun released its energy.

9

At some point after the formation of planetesimals, the seminal event of the solar system occurred: the Sun ignited to become a star. ⬛As dust collapsed in the center of the solar nebula, the gravitational pressure there became high enough to cause a nuclear process known as fusion, in which hydrogen is converted into helium atoms and, in doing so, releases energy. ⬛The ignition swept away what gas and small particles remained in the inner solar system, leaving only bodies too large to be affected—the planetesimals. ⬛The timing is one of the numerous accidents that led to our existence. ⬛Had the Sun ignited before the formation of the planetesimals, all matter in the solar system would have been swept away, and there would have been no Earth or rocky planets!

Look at the four squares ⬛that indicate where the following sentence could be added to the passage

Scientists have developed a theory that explains the processes by which this significant event in the history of the solar system occurred.

Insert Text Questions句子插入题

 

Where would the sentence best fit？Click on a square  sentence to the passage.

10

Meteorites are an important source of information about the birth of the solar system.

 

Prose Summary Questions概要小结题

 

Select 3 answers

ABefore the discovery of ancient meteorites, scientists relied upon CAls for information about the early history of the solar system.

BThe composition of carbonaceous chondrites has helped to support the idea that the Sun and planets formed from the solar nebula.

CPlanetesimals formed in the inner solar system, and by the time the Sun ignited they were large enough to withstand the enormous release of energy.

DThe meteorite Allende contains the oldest particles in the solar system, and some of those particles may be even older than the solar system.

ELike the rocky planets, Allende formed from magnesium-iron materials that condensed as the solar nebula cooled.

FWith the help of meteorites, scientists have determined that the terrestrial planets formed before the Sun became a star, while the gaseous planets formed after the Sun ignited.