太空岩石仍是科学家未解之谜

Space Rock Still a Mystery to Scientists

Oumuamua is the first interstellar object scientists have found passing through our solar system. Interstellar means it came from another star system like our own.

In November 2017, Oumuamua was seen moving between the Sun and the planet Mercury. One year later, there remains¹ a lot of mystery surrounding the space rock. Scientists are still excited about its discovery. But there is disagreement about what it is and how it got here.

A new research paper from Harvard University proposes that Oumuamua may have been sent by an alien life form. The paper has not yet been published.

But based on what many scientists are saying, and what astronomers² know about space rocks, Oumuamua seems to be acting³ like other space rocks.

Here is what scientists do know about Oumuamua: It moved very quickly – at a speed of about 136,000 kilometers an hour.

Michele Bannister is an astrophysicist at Queen's University Belfast in Northern Ireland. She told VOA that scientists only had about three weeks to look at Oumuamua before it moved out of sight.

It is reddish in color and about 400 meters long. In addition, it is 10 times longer than it is wide. Compared to other space objects, 400 meters is very small. So, finding Oumuamua was a major success for astronomers.

Thomas Zurbuchen is an official with NASA, America’s National Aeronautics⁴ and Space Administration. He said that for many years NASA has believed interstellar objects were ‘out there.' "And now―for the first time―we have direct evidence they exist,” he said.

As it moves through space, Oumuamua has been changing speed and direction by itself. Michelle Bannister calls this behavior "non-gravitational acceleration⁵."

Yet there is nothing unusual about such behavior. Bannister says the rock is probably filled with the things that comets and asteroids⁷ usually have a lot of, such as the gas carbon monoxide and the highly poisonous chemical cyanide.

When objects like these get close to the sun, they release gases at high speeds in a process called “sublimation.” This may be what caused Oumuamua to look like it was moving under its own power.

We'll never really know

But that explanation did not stop Harvard scientists Shmuel Bialy and Abraham Loeb from offering a few other possible explanations for the space rock.

By their mathematical estimate, the rock is less than one millimeter thin and very wide. One of their explanations suggests Oumuamua is sort of like a sail on a sailboat. They believe it may use energy from the sun to push itself through space.

The Harvard scientists proposed this because other studies suggest Oumuamua is not a comet or releasing any gas. And Bialy and Loeb have done the math to provide evidence.

The other possibility they suggest is that Oumuamua is a probe sent to our solar system by an alien society.

They have done the math to show how Oumuamua's path might make sense if it were aimed toward Earth.

It is important to note that the Harvard paper has yet to be reviewed by other scientists of similar expertise⁸.

Oumuamua is too small even for our best telescopes to examine. So researchers now have all the information they will ever have.

But there are likely a lot more Oumuamuas out there. Bannister says, “The galaxy⁹ is filled with flying rocks.” She says a countless¹⁰ number of rocks of different sizes are probably moving through the galaxy. And if we are lucky, she says, we should be able to see about one a year.

So, the Earth is getting visitors from other stars. But they are probably just rocks passing through the neighborhood.

I’m Alice Bryant.

Words in This Story

alien – adj. from somewhere other than the planet Earth

comet – n. an object in outer space that develops a long, bright tail when it passes near the sun

asteroid⁶ – n. any one of thousands of small planets that circle around the sun

millimeter – n. a length equal to 1/1000 meter

probe – n. a device that is used to obtain information from outer space

galaxy – n. any one of the very large groups of stars that make up the universe

1 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

2 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》

3 acting   

n.演戏，行为，假装；adj.代理的，临时的，演出用的

参考例句：

• Ignore her,she's just acting.别理她，她只是假装的。
• During the seventies,her acting career was in eclipse.在七十年代，她的表演生涯黯然失色。

4 aeronautics   

n.航空术，航空学

参考例句：

• National Aeronautics and Space undertakings have made great progress.国家的航空航天事业有了很大的发展。
• He devoted every spare moment to aeronautics.他把他所有多余的时间用在航空学上。

5 acceleration   

n.加速，加速度

参考例句：

• All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
• He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。

6 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

7 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

8 expertise   

n.专门知识(或技能等)，专长

参考例句：

• We were amazed at his expertise on the ski slopes.他斜坡滑雪的技能使我们赞叹不已。
• You really have the technical expertise in a new breakthrough.让你真正在专业技术上有一个全新的突破。

9 galaxy   

n.星系；银河系；一群(杰出或著名的人物)

参考例句：

• The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。

10 countless   

adj.无数的，多得不计其数的

参考例句：

• In the war countless innocent people lost their lives.在这场战争中无数无辜的人丧失了性命。
• I've told you countless times.我已经告诉你无数遍了。