VOA慢速英语2021--NASA航天器在太空中发现“嗡嗡声”

Scientists say NASA's most distant exploring spacecraft has recorded what they describe as ‘humming' beyond our solar system.

A new study suggests the continuous hum, detected by the Voyager 1 spacecraft, is caused by waves existing in interstellar space. Voyager 1 left our solar system eight years ago, crossing the border that divides our solar system from interstellar space.

"Interstellar" means "between stars." Scientists say interstellar space begins where the sun's continual flow of material and its magnetic field stop.

Researchers say instruments on Voyager 1 identified the waves as vibrations² in small amounts of gas found in the near-emptiness of interstellar space. The vibrations are also known as plasma³ waves. The spacecraft detected the waves over several years at different radio frequencies.

Results from Voyager 1's findings were recently published in a study appearing in Nature Astronomy.

Astronomers⁴ believe the space that Voyager 1 is passing through -- known as the interstellar medium -- is filled with different kinds of waves, both big and small. Such waves can provide information about the density⁵ of the interstellar medium.

The new research was led by Stella Ocker, a doctoral student at New York's Cornell University and a member of NASA's Voyager 1 team. She was able to make the discovery by examining data slowly sent back by Voyager 1 from about 23 billion kilometers away.

Ocker told Reuters the newly identified plasma waves would be far too weak to be heard with the human ear. "If we could hear (the hum), it would sound like a single steady note, playing constantly but changing very slightly over time."

When the plasma waves are changed to an audio signal, the tone of the sound changes, added James Cordes. He is an astronomy professor at Cornell University and the co-writer of the study. That sound is "a bit eerie⁶," he said.

NASA said in a statement the new discovery may be the first continuous measurement of the density of material in interstellar space. Ocker added: "This detection offers us a new way to measure the density of interstellar space and opens up a new pathway for us to explore the structure of the very nearby interstellar medium."

In the past, Voyager 1 had detected more powerful wave movements in interstellar gas linked to flares⁸ from the sun. But the new study suggests that continuous vibrations unrelated to solar activity could be normal in interstellar space.

The researchers said the findings provide evidence that there is more low-level activity in interstellar gas than scientists had thought.

Ocker said her work can lead to a better understanding of how the interstellar medium interacts with solar wind, the continuous flow of charged particles released by the sun. It can also provide data about how the heliosphere -- a protective bubble for our solar system – is shaped and changed by interstellar conditions.

Voyager 1 was launched in 1977 along with another NASA spacecraft, Voyager 2. Both spacecraft were designed to explore Jupiter and Saturn⁹. Voyager 1 entered interstellar space in 2012 and is still actively¹⁰ collecting and sending data.

In 2019, NASA reported that Voyager 2 had also discovered new details about interstellar space.

The two Voyagers were expected to last only five years. Both long outlasted¹¹ their operational lifetimes, but are expected to run out of power and go silent within five years.

However, Cordes said new spacecraft are already being designed and developed with the goal of traveling even farther beyond our solar system. "That is the message I find appealing: our reach is expanding into interstellar space," he said.

Words in This Story

detect – v. to discover or notice something

vibration¹ – n. a continuous, quick, shaking movement

frequency – n. the number of times a wave, especially of light, sound or radio wave, is produced within a particular period

steady – adj. happening in a smooth, continuous way

constant – adj. happening a lot or all the time

tone – n. a sound with a definite pitch and vibration

eerie – adj. strange in a mysterious way

flare⁷ – n. a sudden increase in brightness

bubble – n. an enclosed or isolate space

1 vibration   

n.颤动，振动；摆动

参考例句：

• There is so much vibration on a ship that one cannot write.船上的震动大得使人无法书写。
• The vibration of the window woke me up.窗子的震动把我惊醒了。

2 vibrations   

n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动

参考例句：

• We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
• I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了，她使我产生良好的感觉。 来自《简明英汉词典》

3 plasma   

n.血浆，细胞质，乳清

参考例句：

• Keep some blood plasma back for the serious cases.留一些血浆给重病号。
• The plasma is the liquid portion of blood that is free of cells .血浆是血液的液体部分，不包含各种细胞。

4 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》

5 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

6 eerie   

adj.怪诞的；奇异的；可怕的；胆怯的

参考例句：

• It's eerie to walk through a dark wood at night.夜晚在漆黑的森林中行走很是恐怖。
• I walked down the eerie dark path.我走在那条漆黑恐怖的小路上。

7 flare   

v.闪耀，闪烁；n.潮红；突发

参考例句：

• The match gave a flare.火柴发出闪光。
• You need not flare up merely because I mentioned your work.你大可不必因为我提到你的工作就动怒。

8 flares   

n.喇叭裤v.（使）闪耀( flare的第三人称单数 )；（使）（船舷）外倾；（使）鼻孔张大；（使）（衣裙、酒杯等）呈喇叭形展开

参考例句：

• The side of a ship flares from the keel to the deck. 船舷从龙骨向甲板外倾。 来自《简明英汉词典》
• He's got a fiery temper and flares up at the slightest provocation. 他是火爆性子，一点就着。 来自《现代汉英综合大词典》

9 Saturn   

n.农神，土星

参考例句：

• 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。
• These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们，土星由较轻的物质构成。

10 actively   

adv.积极地，勤奋地

参考例句：

• During this period all the students were actively participating.在这节课中所有的学生都积极参加。
• We are actively intervening to settle a quarrel.我们正在积极调解争执。

11 outlasted   

v.比…长久，比…活得长( outlast的过去式和过去分词 )

参考例句：

• I outlasted several downsizings but the last one included me. 虽然我坚持到了最后，还是逃不过被裁的命运。 来自互联网
• This clock has outlasted several owners. 这座时钟的寿命比它的几个主人的寿命都长。 来自互联网