科学家发现宇宙第一颗恒星形成证据

Astronomers²: Evidence Found of First Stars

Astronomers have observed what they believe is the formation of the universe 13.6 billion years ago, when the earliest stars were just starting to shine.

The astronomers say their observations may also have measured mysterious dark matter from that time.

The observations however were not in visible light but in weak radio signals from deep space. An antenna³ in the Australian desert captured the radio signals. This receiver is a little bigger than a large television and costs less than $5 million.

Because it records radio signals and not visible light, the antenna can detect objects that are more distant than the famous Hubble Space Telescope.

Judd Bowman of Arizona State University helped to write the report which was published in the journal Nature.

He says the signals came from the very first objects in the universe as it was coming out of darkness 180 million years after the Big Bang.

Many scientists believe the universe began with a huge explosion they call the “Big Bang.” Stars and galaxies⁴ began to appear as the fireball of hydrogen and helium gas expanded and cooled.

Signals believed to come from the earliest stars

Richard Ellis is an astronomer¹ who works at University College London. He says finding the signal from the first stars is more important than the Big Bang. Ellis said, “we are made of star stuff.” By identifying the first signs of stars, “we are seeing the beginnings of our existence,” he said. Ellis was not involved in the project.

The astronomers studied the signals closely. They showed unexpectedly low temperatures and an unusually strong wave. When the astronomers tried to find out why, the best explanation they could find was that dark matter was present.

If true, their observations would be the first confirmation⁵ of dark matter that does not depend on its gravitational effect. For many years, scientists have been looking for dark matter, which is believed to make up a large part of the universe’s mass.

"If confirmed, this discovery deserves two Nobel Prizes" for both capturing the signal of the first stars and for possible dark matter confirmation, said Avi Loeb of Harvard University. He added that independent tests are needed to confirm the findings. Loeb, an astronomer, was not part of the study.

Bowman agreed independent tests are needed. He told the AP his team spent two years confirming their findings.

"It's a time of the universe we really don't know anything about," Bowman said. He said the discovery is "like the first sentence" in the early story of the history of the universe.

However, the findings are nothing that astronomers could actually see. In fact, it is all based on differences in the wavelengths⁷ of radio signals.

Scientists think the early universe was dark and cold, filled only with two gases: hydrogen and helium. Once stars formed, they released ultraviolet light into the dark areas between them. That ultraviolet light changed the energy signature of hydrogen atoms, Bowman said.

Astronomers looked at a specific wavelength⁶. If there were stars and ultraviolet light, they would see one signature. If there were no stars, they would see another. They saw a clear, but very weak signal, providing evidence of stars, probably many of them, Bowman said.

Looking for a weak signal among loud radio "noise"

Finding that first signal was not easy because the Milky⁸ Way alone produces radio wave noise 10,000 times louder, said Peter Kurczynski of the United States National Science Foundation. The government agency provided financial help for the study.

Because the high end of the radio frequency is similar to that of FM radio signals, the astronomers had to go to Australia to escape interference. That was where they put up their antennas⁹.

They worked to confirm what they found, in part by testing it against signals produced in a laboratory. Bowman said it all showed that what they had found was evidence of the existence of the first stars.

Scientists know little about these early stars. They were probably hotter and simpler than modern stars, Ellis and Bowman said. But now that astronomers know where and how to look, others will confirm this and learn more, Bowman noted¹⁰.

The research has yet to establish exactly when these stars turned on, except that they were shining 180 million years after the Big Bang. Scientists had come up with many different time periods for when the first stars began to shine, and 180 million years would be about right under the current theory, said Ellis.

Rennan Barkana is an astrophysicist who has written about the findings. He said when the astronomers studied their results, they found that the hydrogen between stars was "even colder than the coldest we thought possible."

The researchers expected temperatures to be 10 degrees above absolute zero. But they were 5 degrees above absolute zero, or minus 268 degrees Celsius¹¹.

Barkana and others believe this may be caused by dark matter. If confirmed, the discovery could add a new important part to scientists’ thinking about the early universe.

I’m Mario Ritter.

Words in This Story

dark matter – n. material yet to be observed by astronomers, but something they think exists in the universe because of observed gravitational effects

antenna - n. a device for sending or receiving radio or television signals

deserve – v. to have earned because of something

wavelength – n. the distance from one wave of energy to another as it is traveling from point to point

ultraviolet – n. used to describe light that cannot be seen and that has shorter wavelengths than violet light

specific – adj. special; exactly stated

frequency – n. the number of waves of sound or energy that pass by a point every second

absolute zero – n. the temperature that is believed to be the lowest possible temperature

signature – n. an identifying mark or quality

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 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。

4 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。

5 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。

6 wavelength   

n.波长

参考例句：

• The authorities were unable to jam this wavelength.当局无法干扰这一波长。
• Radio One has broadcast on this wavelength for years.广播1台已经用这个波长广播多年了。

7 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

8 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。

9 antennas   

[生] 触角，触须（antenna的复数形式）

参考例句：

• Marconi tied several antennas to kites. 马可尼在风筝上系了几根天线。 来自超越目标英语 第3册
• Radio astronomy today is armed with the largest antennas in the world. 射电天文学拥有世界上最大的天线。

10 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。

11 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。