VOA慢速英语--美国宇航局分享了银河系外行星的第一个证据

NASA Shares First Evidence of Planet Outside Our Galaxy¹

Astronomers² say they have found evidence for the first time of a planet orbiting a star outside our Milky³ Way galaxy.

The evidence was observed by a telescope operated by the American space agency NASA. It is called the Chandra X-ray Observatory⁴. NASA says the orbiting observatory is the world's most powerful X-ray telescope.

NASA recently announced that the observatory might have discovered a new planet in the galaxy known as Messier 51 or M51. The galaxy is popularly known as the "Whirlpool" galaxy. The research recently appeared in the publication Nature Astronomy.

The possible planet is considered an exoplanet. These are planets that orbit a star outside of our own solar system.

NASA says that so far, more than 4,500 exoplanets have been discovered and are considered "confirmed." Thousands of other "candidate" exoplanets have been detected, but require additional study.

But all of these have been observed in the Milky Way galaxy. And NASA says almost all of them are "less than about 3,000 light-years from Earth." Scientists estimate that an exoplanet in the M51 galaxy would be much farther, about 28 million light-years away.

Exoplanets are hard for telescopes to identify. This is because the bright light of the stars they orbit can hide them. The identification process involves searching for drops in the light levels of stars. Such drops could be caused by a planet passing in front of a star.

This method has been used in past observations by NASA telescopes to confirm the presence of planets crossing in front of stars. These movements -- of planets partly blocking light from stars -- are called "transits⁶."

NASA's latest finding is based on a transit⁵ detected by the Chandra X-ray Observatory. But unlike other NASA telescopes which search for drops in observable light, Chandra is designed to detect X-rays.

The observatory "searched for drops in the brightness of X-rays received from X-ray bright binaries⁷," NASA said in a statement. These binaries are defined as bright systems that usually contain a neutron⁸ star or black hole pulling in gas from a closely orbiting star. A neutron star is the unimaginably dense⁹ result of a supergiant star that has collapsed¹⁰ on itself.

The researchers said the activity of binaries causes the material near the neutron star or black hole to become superheated and glow in X-rays. However, the area producing the X-rays is small. It is so small that a planet passing in front of it could block most or all the X-rays, they added.

This method could permit exoplanets "to be detected at much greater distances" than other light-searching systems that depend on optical telescopes, the NASA statement said.

Rosanne Di Stefano is an astrophysicist at the Center for Astrophysics, Harvard & Smithsonian in Cambridge, Massachusetts. She said in a statement that the research team is seeking "to open up a whole new arena¹¹ for finding other worlds by searching for planet candidates at X-ray wavelengths¹²."

Such methods could be used in the future to discover other new planets in distant galaxies¹³, Di Stefano added.

The researchers say more data will be needed to confirm the observation as an actual "extragalactic exoplanet." They say one problem is that the planet candidate has a large orbit. This means it is not expected to pass in front of its binary¹⁴ partner for at least 70 years, blocking any confirmation¹⁵ attempts anytime soon.

However, one co-writer of the study said the team is very confident with its findings. "We know we are making an exciting and bold claim, so we expect that other astronomers will look at it very carefully," said Julia Berndtsson of Princeton University in New Jersey¹⁶. She added: "We think we have a strong argument, and this process is how science works."

Words in This Story

detect – v. to discover or notice something

glow – v. to produce a soft, warm light

optical –adj. relating to or using light, especially light that can be seen with the human eye

arena – n. a place of scene of activity, debate or conflict

confident – adj. sure about your ability to do things well

bold – adj. not afraid of taking risks

1 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。

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 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

4 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。

5 transit   

n.经过，运输；vt.穿越，旋转；vi.越过

参考例句：

• His luggage was lost in transit.他的行李在运送中丢失。
• The canal can transit a total of 50 ships daily.这条运河每天能通过50条船。

6 transits   

通过（transit的复数形式）

参考例句：

• The anomalistic year is the time between successive transits of the Earth through the perihelion. 近点年是地球连续两次通过近日点之间的时间。
• Paradigm study gradually transits to exemplification study in civil society theory. 当前我国的市民社会理论正逐步从范式研究转向范例研究。

7 binaries   

n.一双( binary的名词复数 )；双体；二进制数；双子星

参考例句：

• First MAME4ALL alpha binaries is out for testing purposes. 首个MAME4ALLα预览测试版是为了测试的目而放出的。 来自互联网
• Security updates to the client binaries. 对客户端的二进制文件进行安全更新。 来自互联网

8 neutron   

n.中子

参考例句：

• Neutron is neutral and slightly heavier than the proton.中子是中性的，比质子略重。
• Based on the neutron energy,the value of weighting factor was given.根据中子能量给出了相应的辐射权重因子的数值。

9 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。

10 collapsed   

adj.倒塌的

参考例句：

• Jack collapsed in agony on the floor. 杰克十分痛苦地瘫倒在地板上。
• The roof collapsed under the weight of snow. 房顶在雪的重压下突然坍塌下来。

11 arena   

n.竞技场，运动场所；竞争场所，舞台

参考例句：

• She entered the political arena at the age of 25. 她25岁进入政界。
• He had not an adequate arena for the exercise of his talents.他没有充分发挥其才能的场所。

12 wavelengths   

n.波长( wavelength的名词复数 )；具有相同的/不同的思路；合拍；不合拍

参考例句：

• I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
• Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句

13 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。

14 binary   

adj.二，双；二进制的；n.双(体)；联星

参考例句：

• Computers operate using binary numbers.计算机运行运用二进位制。
• Let us try converting the number itself to binary.我们试一试，把这个数本身变成二进制数。

15 confirmation   

n.证实，确认，批准

参考例句：

• We are waiting for confirmation of the news.我们正在等待证实那个消息。
• We need confirmation in writing before we can send your order out.给你们发送订购的货物之前，我们需要书面确认。

16 jersey   

n.运动衫

参考例句：

• He wears a cotton jersey when he plays football.他穿运动衫踢足球。
• They were dressed alike in blue jersey and knickers.他们穿着一致，都是蓝色的运动衫和灯笼短裤。