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A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return. The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of a stellar mass (the mass of our sun) or greater.
Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is a general consensus that supermassive black holes exist in the centers of most galaxies.
Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as light. Matter falling onto a black hole can form an accretion disk heated by friction, forming some of the brightest objects in the universe. If there are other stars orbiting a large black hole, their orbit can be used to determine its mass and location. These data can be used to exclude possible alternatives (such as neutron stars). In this way, astronomers have identified numerous stellar black hole candidates in binary systems, and established that the core of our Milky Way galaxy contains a supermassive black hole of about 4.3 million solar masses.
1. Which of the following can be inferred from the passage about larger black holes?
(A) They are more likely to be found in the center of galaxies than elsewhere in the universe
(B) They are typically formed when neutron stars collapse
(C) They emit radiation at a higher temperature than do smaller black holes
(D) They affect the orbit of nearby stars
(E) They form accretion disks more frequently than do smaller black holes
2. According to the passage, all of the following would be helpful in discovering new supermassive black holes in the universe except
(A) Observing interactions with matter
(B) Observing interactions with electromagnetic radiation
(C) Observing levels of emitted radiation
(D) Analyzing the orbits of stars
(E) Focusing on the centers of major galaxies
3. The primary purpose of the passage above is to
(A) Analyze a surprising scientific discovery
(B) Argue that black holes are important to the scientific community
(C) Explain how supermassive black holes are formed
(D) Describe a scientific phenomenon
(E) Compare two types of black holes
4. The author points out that a black hole can continue to grow by absorbing mass in order to:
(A) explain how black holes of stellar mass initially form.
(B) explain why supermassive black holes exist in the centers of most galaxies.
(C) provide evidence for why there is a general consensus that supermassive black holes exist.
(D) account for the existence of supermassive black holes.
(E) support the notion that supermassive black holes form only when very massive stars collapse.
5. The passage suggests that neutron stars
(A) are more common than black holes
(B) are found throughout the Milky Way galaxies
(C) can be confused for black holes
(D) are not as bright as the accretion disk in a black hole
(E) have a visible interior
6. The author discusses quantum field theory in order to ________________
A. Highlight the difficulty in detecting some black holes
B. More clearly define what constitutes a black body in thermodynamics
C. Better explain why black holes are “black”
D. Help the reader better understand the general theory of relativity
E. Confirm that a black body in thermodynamics is similar to a black hole in space
参考答案： DCDDCA
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发表于 2021-7-28 06:13:16
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