2006年VOA标准英语-Pluto Demoted, No Longer a Planet

By David McAlary
Washington
24 August 2006
 
Pluto¹ is no longer a planet. The world's top group of astronomers³, the International Astronomical⁴ Union, has stripped Pluto of the status it has held since its discovery 76 years ago. The body decided⁵ that, when it comes to planets, size matters.

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The International Astronomical Union's general assembly, meeting in Prague, has voted to accept only eight planets in our solar system. A U.S. astronomer² who was there, Richard Binzel of the Massachusetts Institute of Technology, says the astronomical community has decided Pluto is not a planet, but something else.

"The community has decided that Pluto is best described as a 'dwarf⁶' planet," said Binzel.

This is a big decline in Pluto's fortunes since the astronomers began their meeting on August 14. At that time, they faced a resolution hammered out by Binzel and several others not only keeping Pluto as a planet, but adding three more - Pluto's largest moon, Charon; the asteroid⁷ Ceres; and a larger, more distant body discovered last year, provisionally named Xena. 

		Pluto, left, and Charon seen through NASA's Hubble Space Telescope

That resolution defined a planet as any body orbiting a star that has enough gravity to pull itself into a sphere. Charon was included because it and Pluto orbit each other.

But Binzel says most astronomers at the assembly favored a more exclusive definition that considers more than just a body's shape.

"It's simply a matter of what criterion is the most important?" explained Binzel. "Is the shape of the object the most important criterion, or is it how it orbits? Ultimately, of the members present who calculate things like orbits, that was deemed to be a more important consideration. So it was just a change of emphasis."

The newly-accepted definition says a planet must be not only spherical⁸, but also must have cleared away all other objects in its vicinity. Its gravitational force must either have either pulled them in and absorbed them or flung them away. The icy, distant bodies Pluto, Charon, and Xena orbit among thousands of other similar bodies in a region of the solar system beyond Neptune⁹ called the Kuiper Belt. Furthermore, Pluto's orbit overlaps¹⁰ Neptune's. Ceres circles among a large number of astreroids. In each case, these dwarfs¹¹ are too small to exert enough gravity to give them more space.

Pressure has been building to demote Pluto since the Kuiper Belt was discovered in 1992, but California Institute of Technology astronomer Michael Brown says his discovery of Xena last year forced the issue.

"I may go down in history as the guy who killed Pluto," said Brown. "It's not necessarily what I set out to do when I came to work that morning, but sometimes these things just happen."

Of course, millions of textbooks must be revised and schoolchildren the world over taught that our sun now has only eight planets.

High school science teacher John Whitsett of Fond du Lac, Wisconsin, the president-elect of the U.S. National Science Teachers Association, says the change is positive because it shows students that science is not merely a collection of static facts.

"Teachers can then really demonstrate that science is a problem solving process, and that we're constantly having to modify our body of knowledge based upon the information we come up with later," noted¹² Whitsett.

1 Pluto   

n.冥王星

参考例句：

• Pluto is the furthest planet from the sun.冥王星是离太阳最远的行星。
• Pluto has an elliptic orbit.冥王星的轨道是椭圆形的。

2 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。

3 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》

4 astronomical   

adj.天文学的，（数字）极大的

参考例句：

• He was an expert on ancient Chinese astronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling for astronomical prices.乡村的房价正在飙升。

5 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

6 dwarf   

n.矮子，侏儒，矮小的动植物；vt.使…矮小

参考例句：

• The dwarf's long arms were not proportional to his height.那侏儒的长臂与他的身高不成比例。
• The dwarf shrugged his shoulders and shook his head. 矮子耸耸肩膀，摇摇头。

7 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

8 spherical   

adj.球形的；球面的

参考例句：

• The Earth is a nearly spherical planet.地球是一个近似球体的行星。
• Many engineers shy away from spherical projection methods.许多工程师对球面投影法有畏难情绪。

9 Neptune   

n.海王星

参考例句：

• Neptune is the furthest planet from the sun.海王星是离太阳最远的行星。
• Neptune turned out to be a dynamic,stormy world.海王星原来是个有生气、多风暴的世界。

10 overlaps   

v.部分重叠( overlap的第三人称单数 )；（物体）部份重叠；交叠；（时间上）部份重叠

参考例句：

• The style in these two books largely overlaps. 这两本书的文体有许多处是一致的。 来自《现代英汉综合大词典》
• The new office overlaps the functions of the one already in existence. 新机构的职能与那个现存机构的职能部分重叠。 来自辞典例句

11 dwarfs   

n.侏儒，矮子（dwarf的复数形式）vt.（使）显得矮小（dwarf的第三人称单数形式）

参考例句：

• Shakespeare dwarfs other dramatists. 莎士比亚使其他剧作家相形见绌。 来自《简明英汉词典》
• The new building dwarfs all the other buildings in the town. 新大楼使城里所有其他建筑物都显得矮小了。 来自辞典例句

12 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。