VOA慢速英语2020 太阳系可能是星系碰撞创造的

A violent event of a massive size may have led to the birth of our solar system, scientists say. That event was the crashing of two galaxies¹.

The coming together of our galaxy² and a smaller one caused countless³ stars to form in the Milky⁴ Way more than 4.5 billion years ago, scientists reported last week.

The smaller galaxy is called Sagittarius. It is 10,000 times smaller than the Milky Way.

A crash between galaxies usually does not involve stars hitting each other, the scientists noted⁵. But it can create conditions for star formation. For example, it can increase the amount of gas in a galaxy or cause gas clouds to come together.

The Reuters news agency says the two galaxies first crashed more than six billion years ago. Since then, Sagittarius has passed through the Milky Way and its nearly 100 billion stars two more times. The scientists link all three events to a sharp jump in Milky Way star formation.

Scientific data show a long period of star-formation -- from 6.2 billion to 4.2 billion years ago -- linked to the first crash. That data comes from the European Space Agency's Gaia space observatory⁶. Scientists believe two other star-formation surges linked to the colliding galaxies took place 1.9 billion years ago and 1 billion years ago. Each one lasted a few hundred million years.

Tomás Ruiz-Lara is an astronomer⁷ at the Instituto de Astrofísica de Canarias in Spain. He was the lead writer of a report on the research.

He says galaxy crashes are not like car crashes. Some parts of Sagittarius and the Milky Way intersect, but a crash between stars would be "really, really rare," he said.

The "crash" changed our galaxy's speed of star formation, Ruiz-Lara explained.

"First, we have the addition of material, gas, from Sagittarius that increases the amount of gas in our galaxy to form new stars," he said. Second, there is the collision between gas clouds from Sagittarius and gas clouds from the Milky Way, which also led to star formation. Third, the crash causes gravitational instabilities that can lead to star formation, he said. This happens because of changes in the density⁸ of the gaseous⁹ matter in the usually low-density space between star systems.

The report on galactic interactions appears in the publication Natural Astronomy.

I'm Alice Bryant.

Words in This Story

solar system - n. our sun and the planets that move around it

galaxy - n. any of the very large groups of stars that makes up the universe

Milky Way - n. the galaxy in which we live that contains the stars that make up the Milky Way

data - n. facts or information used usually to calculate, analyze¹⁰, or plan something

surge - n. a sudden large increase

intersect - v. to meet and cross at one or more points

instability - n. the state of being likely to change

density - n. the quality of having parts that are close together

1 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。

2 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。

3 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。

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 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。

6 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。

7 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。

8 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。

9 gaseous   

adj.气体的，气态的

参考例句：

• Air whether in the gaseous or liquid state is a fluid.空气，无论是气态的或是液态的，都是一种流体。
• Freon exists both in liquid and gaseous states.氟利昂有液态和气态两种形态。

10 analyze   

vt.分析，解析 (=analyse)

参考例句：

• We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
• The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。