VOA慢速英语2020--科学家发现两个黑洞合并成前所未有的大小

Black holes are becoming stranger — even to scientists who study planets and other objects in outer space.

Astronomers¹ recently reported the discovery of the signal from a violent collision of two black holes. The event, which took place long ago, created a new black hole of a size that scientists had never seen before.

California Institute of Technology physicist² Alan Weinstein was part of the discovery team. He noted³ that the finding was the "biggest bang" ever observed by human beings since the Big Bang.

The Big Bang is a term many astronomers use to explain the beginning of the universe.

Black holes are compact areas of space. They are so dense⁴ that not even light can escape. Until recently, astronomers had observed them in two general sizes.

There are "small" ones called stellar black holes. These black holes are formed when a star collapses⁶. They are about the size of a small city.

There are also supermassive black holes. These black holes are millions, maybe billions, of times more massive than our sun.

Astronomers' calculations suggest that anything in between the two sizes did not make sense. That was because stars that grew too big before collapse⁵ would generally destroy themselves, leaving no black holes.

Nelson Christensen is research director of the French National Centre for Scientific Research. He says scientists thought that star collapses could not create stellar black holes much bigger than 70 times the mass of our sun.

Then in May 2019 two sensors⁷ received a signal that turned out to be the energy from two stellar black holes crashing into each other. One was 66 times the mass of our sun. The other was 85 times the mass of the sun.

The result: The first ever discovered intermediate black hole, at 142 times the mass of the sun. The word intermediate suggests being in the middle of a process or development.

In the collision, a large amount of energy was lost. The energy was in the form of a gravitational wave, a ripple⁸ in space that travels at the speed of light.

It was that wave that physicists⁹ in the United States and Europe, using detectors¹¹ called LIGO and Virgo, captured last year. After studying the signal and reexamining their work, scientists published the results this week in Physical Review Letters and Astrophysical Journal Letters.

Because the detectors receive the gravitational waves as audio signals, scientists actually heard the collision. For all the violence, the signal lasted only one-tenth of a second.

"It just sounds like a thud," Weinstein said. "It really doesn't sound like much on a speaker."

This crash happened about 7 billion years ago, when the universe was about half its current age. It was only detected now because the collision was so far away.

Black hole collisions have been observed before. But the black holes involved were smaller to begin with. Even after the collision, they did not grow beyond the size of normal stellar black holes.

Scientists still do not know how supermassive black holes at the center of galaxies¹² formed, Christensen said, but this new discovery may offer a clue.

I'm John Russell.

Words in This Story

collision – n. an act of colliding, such as a crash in which two or more things or people hit each other

bang – n. a sudden, loud noise

compact – adj. closely or firmly joined together

calculation – n. an estimate or prediction

ripple – n. something that passes or spreads through or over someone or something; a shape having small waves

detector¹⁰ – n. a device that can tell if a substance or object is present; a device that measures the presence of something

thud – n. a loud sound made especially when a heavy object hits something

1 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

2 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

3 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

4 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

5 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

6 collapses   

折叠( collapse的第三人称单数 )； 倒塌； 崩溃； （尤指工作劳累后）坐下

参考例句：

• This bridge table collapses. 这张桥牌桌子能折叠。
• Once Russia collapses, the last chance to stop Hitler will be gone. 一旦俄国垮台，抑止希特勒的最后机会就没有了。

7 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

8 ripple   

n.涟波，涟漪，波纹，粗钢梳；vt.使...起涟漪，使起波纹； vi.呈波浪状，起伏前进

参考例句：

• The pebble made a ripple on the surface of the lake.石子在湖面上激起一个涟漪。
• The small ripple split upon the beach.小小的涟漪卷来，碎在沙滩上。

9 physicists   

物理学家( physicist的名词复数 )

参考例句：

• For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技
• Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

10 detector   

n.发觉者，探测器

参考例句：

• The detector is housed in a streamlined cylindrical container.探测器安装在流线型圆柱形容器内。
• Please walk through the metal detector.请走过金属检测器。

11 detectors   

探测器( detector的名词复数 )

参考例句：

• The report advocated that all buildings be fitted with smoke detectors. 报告主张所有的建筑物都应安装烟火探测器。
• This is heady wine for experimenters using these neutrino detectors. 对于使用中微子探测器的实验工作者，这是令人兴奋的美酒。 来自英汉非文学 - 科技

12 galaxies   

星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）

参考例句：

• Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。