Question

    Scientists have discovered a “monster black hole” so massive that, in theory, it shouldn’t exist. It’s a stellar (恒星) black hole — the type that forms after stars die, collapse, and explode. Researchers had previously believed that the size limit was no more than 20 times the mass of our sun because as these stars die, they lose most of their mass through explosions that expel (排出) matter and gas swept away by stellar winds.

This theory has now been toppled by LB-1, the newly discovered black hole. Located about 15,000 light years away, it has a mass 70 times greater than our sun, according to a press release from the Chinese Academy of Sciences.

The findings were published by Chinese researchers in the journal Nature on Wednesday. “Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution,” said Liu Jifeng, head of the team that made the discovery.

“LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation.”

Scientists are now scratching their heads at how LB-1 got so huge.

The Chinese team has proposed a number of theories. LB-1’s sheer size suggests that it “was not formed from the collapse of only one star,” the study said — instead, it could potentially be two smaller black holes orbiting each other.

Another possibility is that it formed from “fallback supernova.” This is when a supernova — the last stage of an exploding star — ejects (排出) material during the explosion, which then falls back into the supernova, creating a black hole.

This fallback formation is theoretically possible, but scientists have never been able to prove or observe it. If this is how LB-1 formed, then we may have “direct evidence for this process” for the first time, the study said.

There are several types of black holes and stellar black holes like LB-1 are on the smaller side, according to NASA. Supermassive black holes are much bigger — they can be billions of times the mass of our sun.

Scientists believe supermassive black holes may be connected to the formation of galaxies, as they often exist at the center of the mass star stems but it is still not clear exactly how, or which form first.

1.Why does the writer write the article?

A.To report the great achievement Chinese scientists have made in black hole theory.

B.To inform the readers of the basic knowledge about the black hole.

C.To share with the readers the new development of the black hole discovery.

D.To demonstrate the significance of discovering new black holes for science.

2.What does the underlined word “toppled” mean in the second paragraph?

A.overturned B.supported C.suspected D.tested

3.Which of the following about LB-1 is true to the passage?

A.It is the biggest black hole ever discovered.

B.It lost only a small part of its mass through explosion.

C.It couldn’t have been formed from the collapse of one star,

D.Its discovery may lead to some breakthrough in the “fallback formation theory”.

4.Which of the following is right according to the passage?

A.If the sun in our galaxy dies some of its mass will be taken away by stellar winds.

B.A massive supernova will be formed and then exploded if the sun in our galaxy dies.

C.“The Milky Way” was formed after a supermassive black hole collapsed and exploded.

D.If “the Milky Way” dies, a supermassive black hole will be formed after its death.

Answer

1.C

2.A

3.D

4.A

【解析】

本文是说明文。研究人员以前认为，恒星消失后形成黑洞的大小不超过太阳质量的20倍，但是新发现的黑洞LB-1的质量是太阳的70倍。关于超大质量黑洞的形成，科学家们提出两种理论，一种是认为它可能是两个相互环绕的较小的黑洞，一种认为它是由“回退超新星”形成的。科学家认为，超大质量黑洞可能与星系的形成有关。

1.推理判断题。文章介绍了关于超大质量的黑洞LB-1的形成原因，科学家们提出了两个理论。一种理论是认为它可能是两个相互环绕的较小的黑洞，一种理论认为它是由“回退超新星”形成的。科学家认为，超大质量黑洞可能与星系的形成有关。因此作者写这篇文章是为了给读者介绍关于黑洞发现的新进展。故选C项。

2.词义猜测题。第1段中提到Researchers had previously believed that the size limit was no more than 20 times the mass of our sun(研究人员以前认为，这些黑洞的大小限制不超过太阳质量的20倍)，第2段中提到it has a mass 70 times greater than our sun(它的质量是太阳的70倍)，因此可以推断，以前关于黑洞的大小限制的理论被新发现的超大质量黑洞LB-1所推翻。overturn意思为“推翻，倾覆”。故选A项。

3.细节理解题。根据第7段中的Another possibility is that it formed from “fallback supernova.”可知，关于LB-1的形成，科学家们提出另一种可能性，认为LB-1是由“回退超新星”形成的；根据第8段中的If this is how LB-1 formed, then we may have “direct evidence for this process” for the first time, the study said.可知，科学家们认为如果这是LB-1的形成方式，那么这可能是第一次有“这一过程的直接证据”。因此LB-1的发现可能会给“回退形成理论”带来一些突破。故选D项。

4.细节理解题。根据第1段中的Researchers had previously believed that the size limit was no more than 20 times the mass of our sun because as these stars die, they lose most of their mass through explosions that expel (排出) matter and gas swept away by stellar winds.可知，研究人员此前认为，其大小限制不超过太阳质量的20倍，因为当这些恒星死亡时，它们会通过爆炸失去大部分质量，爆炸会释放出被恒星风吹走的物质和气体。由此可知，如果我们星系中的太阳死亡，它的一些质量将被恒星风带走。故选A项。