Câu hỏi: 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/)
According to paragraph 2, what is NOT mentioned about the r-process?
A. R-process happens before the radioactive decay process.
B. R-process reactions are similar to thermonuclear weapon explosions.
C. R-process is a set of nuclear reactions initiated by neuron-star collision.
D. It is responsible for the creation of approximately half of the atomic nuclei heavier than iron.
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/)
According to paragraph 2, what is NOT mentioned about the r-process?
A. R-process happens before the radioactive decay process.
B. R-process reactions are similar to thermonuclear weapon explosions.
C. R-process is a set of nuclear reactions initiated by neuron-star collision.
D. It is responsible for the creation of approximately half of the atomic nuclei heavier than iron.
Theo đoạn 2, những gì không được đề cập về quá trình R?
A. Quá trình R xảy ra trước quá trình phân rã phóng xạ
B. Phản ứng quá trình R tương tự như vụ nổ vũ khí nhiệt hạch
C. Quá trình R là một tập hợp các phản ứng hạt nhân được bắt đầu bởi sự va chạm giữa các ngôi sao neutron
D. Nó chịu trách nhiệm tạo ra khoảng một nửa số hạt nhân nguyên tử nặng hơn sắt
Căn cứ vào thông tin đoạn đầu:
They're known as the r-process … Afterward, those nuclei would become transformed in a process known as radioactive decay. ... 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. (Chúng được gọi là quá trình R. ... Sau đó, những hạt nhân đó sẽ bị biến đổi trong một quá trình được gọi là phân rã phóng xạ. .... Khoảng một nửa trong số các nguyên tố nặng hơn sắt được cho là sẽ được tạo ra trong quá trình R. Việc tìm ra stronti trong vụ va chạm gần đây cuối cùng đã đưa ra hầu hết các bằng chứng trực tiếp cho thấy các vụ va chạm sao neutron thực sự kích hoạt quá trình R.)
A. Quá trình R xảy ra trước quá trình phân rã phóng xạ
B. Phản ứng quá trình R tương tự như vụ nổ vũ khí nhiệt hạch
C. Quá trình R là một tập hợp các phản ứng hạt nhân được bắt đầu bởi sự va chạm giữa các ngôi sao neutron
D. Nó chịu trách nhiệm tạo ra khoảng một nửa số hạt nhân nguyên tử nặng hơn sắt
Căn cứ vào thông tin đoạn đầu:
They're known as the r-process … Afterward, those nuclei would become transformed in a process known as radioactive decay. ... 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. (Chúng được gọi là quá trình R. ... Sau đó, những hạt nhân đó sẽ bị biến đổi trong một quá trình được gọi là phân rã phóng xạ. .... Khoảng một nửa trong số các nguyên tố nặng hơn sắt được cho là sẽ được tạo ra trong quá trình R. Việc tìm ra stronti trong vụ va chạm gần đây cuối cùng đã đưa ra hầu hết các bằng chứng trực tiếp cho thấy các vụ va chạm sao neutron thực sự kích hoạt quá trình R.)
Đáp án B.