VOA慢速英语--研究称大型行星可能撞上了年轻的木星

Study: Massive Planet May Have Crashed into Young Jupiter

A new study suggests that the planet Jupiter may have been hit a long time ago by a still-developing planet, one about 10 times the size of Earth.

Scientists believe the head-on crash took place not long after Jupiter was formed.

Scientists say such a violent collision could explain conditions inside the center of the planet.

A report on the study appeared in the publication Nature.

Astronomers² believe the collision may have happened several million years after the formation of our sun. The solar system – made up of the sun and eight major planets – was formed about 4.6 billion years ago.

Jupiter is massive - more than two times the size of all other planets in the solar system combined. Jupiter is a gaseous³ planet, made up mostly of hydrogen and helium. Scientists believe it took shape when gravity pulled in gas and dust left over from the sun’s formation.

Researchers have long sought to understand more about Jupiter. In recent years, the U.S. space agency NASA has carried out research on the planet. NASA’s Juno spacecraft, launched in 2011, uses instruments to measure the planet’s gravitational and magnetic fields.

Juno has made interesting findings about Jupiter. It showed that Jupiter likely has a “diluted⁴” center, one mixed with both light and heavy materials. In the past, scientists theorized that the planet likely had a dense⁵, solid core.

In the latest study, researchers examined data and other measurements collected by Juno. They used this information to build models to predict what the planet’s core is made of and how it is structured.

Their models supported the theory that a head-on collision took place between Jupiter and a still-developing planet. The team’s findings suggest the object that hit Jupiter would have been about 10 times the size of Earth. Such a crash, involving the two massive planets, could have broken apart Jupiter’s dense core and mixed light elements with heavy ones.

Andrea Isella is an astronomer¹ with Rice University in Texas. He helped lead the research.

Isella said in a statement he was at first unsure about the collision theory when the idea was presented. “It sounded very unlikely to me,” he said, “like a one-in-a-trillion probability.”

But Isella said he began to support the theory when he saw calculations made by another researcher. That researcher was Shang-Fei Liu, an astronomer from China’s Sun Yat-sen University. He said the calculations – which came from computer modeling methods – changed his mind that the theory “was not so improbable.”

The study found there was at least a 40 percent chance that Jupiter would collide with a still-forming planet within its first few million years.

Isella said that scientists already believed such large collisions might have been common while the solar system was still developing. “For example, we believe that our moon formed after such an event,” he told the Reuters news agency. “However, the impact that we postulate⁶ for Jupiter is a real monster.”

Under the theory, the still-developing planet - also known as a protoplanet - would have been swallowed up by Jupiter. Liu said that if the collision had not happened, the protoplanet would have likely went on to become a massive gas planet in our solar system.

The researchers also suggest that a similar collision, involving the planet Saturn⁷, may have happened while the solar system was still young. This may explain the structural⁸ differences that exist between Jupiter and Saturn, they said.

I’m Bryan Lynn.

Words in This Story

diluted – adj. made weaker by mixing in something else

core – n. the center or most important part of something

calculation – n. a mathematical estimate of something

impact – n. the force with which one thing hits another

postulate – v. to suggest or accept that a theory or idea is true

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 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。

4 diluted   

无力的，冲淡的

参考例句：

• The paint can be diluted with water to make a lighter shade. 这颜料可用水稀释以使色度淡一些。
• This pesticide is diluted with water and applied directly to the fields. 这种杀虫剂用水稀释后直接施用在田里。

5 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。

6 postulate   

n.假定，基本条件；vt.要求，假定

参考例句：

• Let's postulate that she is a cook.我们假定她是一位厨师。
• Freud postulated that we all have a death instinct as well as a life instinct.弗洛伊德曾假定我们所有人都有生存本能和死亡本能。

7 Saturn   

n.农神，土星

参考例句：

• 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。
• These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们，土星由较轻的物质构成。

8 structural   

adj.构造的，组织的，建筑（用）的

参考例句：

• The storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
• The North American continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。