Câu hỏi:
26/04/2022 3,096
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Astronomers have for the first time definitively ID’d the birth of a specific heavy element during a neutron-star smashup. They found strontium. And it showed up in the wavelengths of light — or spectra — making up this collision’s afterglow.
Scientists had assumed that a collision by two super-dense objects, such as neutron stars, would trigger a chain of nuclear reactions. They’re known as the r-process. In such an environment, the nuclei of atoms could rapidly gobble up neutrons. Afterward, those nuclei would become transformed in a process known as radioactive decay. The r-process was seen as a way to transform old, smaller elements into newer, bigger ones. About half of all elements heavier than iron were thought to be made in the r-process. Finding strontium in the recent collision at last offered the most direct evidence yet that neutron-star collisions really do trigger the r-process.
Physicists had long predicted that silver, gold and many other elements more massive than iron formed this way. But scientists weren’t sure where those r-process reactions took place. After all, no one had directly seen the r-process underway in a celestial event. Or they didn’t until the merger of two neutron stars in 2017. Scientists quickly analyzed light given off by that cataclysm. In it, they found evidence of the birth of a hodgepodge of heavy elements. All would seem to have come from the r-process.
The researchers were examining mostly very heavy elements — ones whose complex atomic structures can generate millions of spectral features. And all of those features were not yet fully known, Watson points out. This made it extremely difficult to tease apart which elements were present, he says.
Strontium, however, is relatively light compared to other r-process elements. And its simple atomic structure creates a few strong and well-known spectral clues. So Watson and his colleagues expanded their analysis to consider it. In doing so, they turned up the clear "fingerprint" of strontium. It emerged in light collected by the Very Large Telescope in Chile within a few days of the neutron-star collision. Seeing strontium in the afterglow wasn’t all that unexpected, says Brian Metzger. He’s an astrophysicist at Columbia University in New York City and not involved in the new work. Strontium, he notes, “does tell us something interesting” about the elements formed during the neutron-star collision.
(Source: https://www.sciencenewsforstudents.org/)
Which best serves as the title for the passage?
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Astronomers have for the first time definitively ID’d the birth of a specific heavy element during a neutron-star smashup. They found strontium. And it showed up in the wavelengths of light — or spectra — making up this collision’s afterglow.
Scientists had assumed that a collision by two super-dense objects, such as neutron stars, would trigger a chain of nuclear reactions. They’re known as the r-process. In such an environment, the nuclei of atoms could rapidly gobble up neutrons. Afterward, those nuclei would become transformed in a process known as radioactive decay. The r-process was seen as a way to transform old, smaller elements into newer, bigger ones. About half of all elements heavier than iron were thought to be made in the r-process. Finding strontium in the recent collision at last offered the most direct evidence yet that neutron-star collisions really do trigger the r-process.
Physicists had long predicted that silver, gold and many other elements more massive than iron formed this way. But scientists weren’t sure where those r-process reactions took place. After all, no one had directly seen the r-process underway in a celestial event. Or they didn’t until the merger of two neutron stars in 2017. Scientists quickly analyzed light given off by that cataclysm. In it, they found evidence of the birth of a hodgepodge of heavy elements. All would seem to have come from the r-process.
The researchers were examining mostly very heavy elements — ones whose complex atomic structures can generate millions of spectral features. And all of those features were not yet fully known, Watson points out. This made it extremely difficult to tease apart which elements were present, he says.
Strontium, however, is relatively light compared to other r-process elements. And its simple atomic structure creates a few strong and well-known spectral clues. So Watson and his colleagues expanded their analysis to consider it. In doing so, they turned up the clear "fingerprint" of strontium. It emerged in light collected by the Very Large Telescope in Chile within a few days of the neutron-star collision. Seeing strontium in the afterglow wasn’t all that unexpected, says Brian Metzger. He’s an astrophysicist at Columbia University in New York City and not involved in the new work. Strontium, he notes, “does tell us something interesting” about the elements formed during the neutron-star collision.
(Source: https://www.sciencenewsforstudents.org/)
Which best serves as the title for the passage?
Đáp án chính xác
Câu hỏi trong đề:
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Trả lời:
Giải bởi Vietjack
Đáp án D
Câu nào sau đây thích hợp nhất làm tiêu đề cho đoạn văn?
A. Sóng hấp dẫn liên kết với va chạm sao neutron
B. Một vụ va chạm sao neutron gần đó có thể gây ra thiên tai trên Trái đất
C. Va chạm sao neutron làm rung chuyển không gian và thời gian
D. Nguyên tố nặng được xác định từ vụ va chạm sao neutron
Căn cứ vào thông tin đoạn đầu:
Astronomers have for the first time definitively ID'd the birth of a specific heavy element during a neutron-star smashup. They found strontium. And it showed up in the wavelengths of light — or spectra — making up this collision's afterglow. (Các nhà thiên văn học lần đầu tiên xác định rõ ràng sự ra đời của một nguyên tố nặng cụ thể trong một vụ va chạm sao neutron. Họ tìm thấy stronti. Và nó xuất hiện trong các bước sóng ánh sáng - hoặc quang phổ - tạo nên phát quang của vụ va chạm này.)
Như vậy, đoạn văn đang nói về một nguyên tố nặng mới được xác định từ vụ va chạm sao neutron là stronti.
Nhà sách VIETJACK:
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