VOA慢速英语--天文学家发现了快速射电爆发的源头

A little luck helped astronomers² solve a mystery in space: What causes powerful but super-fast energy signals that move through the universe?

Scientists have known about these signals, called fast radio bursts, for about 13 years. And they have seen them coming from outside our galaxy³. This makes it harder to know what is causing them. What makes it even harder is that they happen so fast -- in a few one-thousandths of a second.

Then in April, a rare but much weaker burst from inside our own galaxy was found by two dissimilar telescopes. One of the telescopes was a California doctoral student's handmade equipment, which included metal cookware. The other was based at a $20-million Canadian space observation center.

They linked the fast radio burst to a strange kind of star called a magnetar that is 32,000 light-years from Earth. That information comes from four studies in Wednesday's journal publication Nature.

It was not only the first fast radio burst linked to a source; it was also the first coming from our galaxy. Astronomers say there could be other sources for these bursts. But they are now sure about one of the sources: magnetars.

Magnetars have 1.5 times the mass of our sun, crowded into a space the size of New York's Manhattan area. They have huge magnetic fields that are full of energy, and sometimes bursts of X-rays and radio waves suddenly come from them. That information comes from Ziggy Pleunis. He is an astrophysicist at McGill University and co-writer of the Canadian study.

The magnetic field around these magnetars "is so strong any atoms nearby are torn apart," said astronomer¹ Casey Law. He is with the California Institute of Technology (Caltech) and was not involved in the research.

There are maybe 12 or so of these magnetars in our galaxy. They are very young and part of the star birth process. And our Milky⁴ Way galaxy is not as full of star births as other galaxies⁵, said Shami Chatterjee of Cornell University. He was not part of either discovery team.

This burst in less than a second had about the same amount of energy that our sun produces in a month. And that is still a lot weaker than radio bursts from outside our galaxy, said Christopher Bochenek. The Caltech radio astronomer helped discover the burst with his handmade equipment.

The radio bursts are not dangerous to us, not even the more powerful ones from outside our galaxy, astronomers say.

The ones that come from outside our galaxy and travel millions or billions of light-years are very powerful. They are tens of thousands to millions of times more powerful than anything we have found in our galaxy, explains Daniele Michilli, an astrophysicist at McGill University. He is co-writer of the study and part of the Canadian team.

Scientists think the bursts may happen more than 1,000 times a day outside our galaxy. But finding them is not easy.

"You had to be looking at the right place at the right millisecond," Cornell's Chatterjee said. "Unless you were very, very lucky, you're not going to see one of these."

Astronomers have no idea how often the bursts happen inside our own Milky Way galaxy.

"We still don't know how lucky we got," Bochenek said. "This could be a once-in-five-year thing or there could be a few events to happen each year."

Bochenek's antennae⁶ cost about $15,000. Each is "the size of a large bucket," he said. It's a piece of 6-inch metal pipe with two pieces of round metal cookware around it, the doctoral student explained. They are simplistic instruments designed to look at a huge piece of the sky. And they are meant to see only the brightest of radio flashes.

Bochenek imagined he had possibly a 1-in-10 chance of catching⁸ a fast radio burst in a few years. But after just one year, he made a valuable discovery.

The Canadian observatory⁹ in British Columbia is much more developed but is aimed at a much smaller piece of the sky. And it was able to find the source of the magnetar in the constellation¹⁰ Vulpecula.

The bursts are affected¹¹ by all the material they pass through in space. This might help astronomers understand and map the unseen-to-us material between galaxies and "weigh" the universe, said Jason Hessels. He is chief astronomer for the Netherlands Institute for Radio Astronomy¹² and was not part of the research.

Astronomers have had as many as 50 different ideas about what causes these fast radio bursts, including aliens. They say that magnetars may not be the only answer.

Words in This Story

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

source – n. the cause or origin of something

x-ray – n. powerful invisible rays that can pass through various objects

antenna⁷ – n. a device (such as a wire or a metal rod) for sending or receiving radio or television signals

bucket – n. an open container with a handle that is used for carrying things, such as liquids

alien – n. a creature that comes from somewhere other than the planet Earth

1 astronomer   

n.天文学家

参考例句：

• A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
• He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。

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 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。

4 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。

5 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。

6 antennae   

n.天线；触角

参考例句：

• Sometimes a creature uses a pair of antennae to swim.有时某些动物使用其一对触须来游泳。
• Cuba's government said that Cubans found watching American television on clandestine antennae would face three years in jail.古巴政府说那些用秘密天线收看美国电视的古巴人将面临三年监禁。

7 antenna   

n.触角，触须；天线

参考例句：

• The workman fixed the antenna to the roof of the house.工人把天线固定在房顶上。
• In our village, there is an antenna on every roof for receiving TV signals.在我们村里，每家房顶上都有天线接收电视信号。

8 catching   

adj.易传染的，有魅力的，迷人的，接住

参考例句：

• There are those who think eczema is catching.有人就是认为湿疹会传染。
• Enthusiasm is very catching.热情非常富有感染力。

9 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。

10 constellation   

n.星座n.灿烂的一群

参考例句：

• A constellation is a pattern of stars as seen from the earth. 一个星座只是从地球上看到的某些恒星的一种样子。
• The Big Dipper is not by itself a constellation. 北斗七星本身不是一个星座。

11 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

12 astronomy   

n.天文学

参考例句：

• Mathematics is connected with astronomy.数学与天文学有联系。
• Astronomy is an abstract subject.天文学是一门深奥的学科。