2006年VOA标准英语-Scientists Find '10th Planet' Bigger Than

By David McAlary
Washington
01 February 2006

Claims that our solar system has a 10th planet beyond Pluto¹ are supported by a new finding by German and French astronomers³.  They calculate that it is bigger than Pluto. In the debate over whether this object is a planet or not, size might be the determining factor.

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Artists concept of the view from UB313 looking back towards the distant sun  
  

The definition of a planet is a hot topic among astronomers these days after last year's discovery of an icy body beyond Pluto's orbit known only by its scientific designation 2003 UB313.

Many, like Scott Sheppard of the Carnegie Institution in Washington, argue that this new object should not be considered a planet, and for that matter, nor should Pluto. He says both are typical, but larger members of the thousands of icy bodies circling beyond Neptune⁴ in the so-called Kuiper Belt.

Unlike the eight major planets, their orbits are not independent, but are attuned⁵ to that of Neptune, and their gravitational fields do not dominate their local environments.

"Pluto and 2003 UB313 and the rest of the thousands of Kuiper Belt objects beyond Neptune, since they formed and evolved in a very similar manner, should be grouped together," he said.  "So I would personally consider Pluto and the rest of the Kuiper Belt objects not really planets, but the third domain⁶ of the solar system or something like that."

The third domain refers to the fact that Pluto and its Kuiper Belt cousins are ice covered, in contrast to the inner planets with rocky surfaces like Earth and the outer gas giants Jupiter and Saturn⁷.

But Sheppard admits there are other ways to classify planets that that would not exclude Pluto and its newly discovered distant neighbor.  They would include anything orbiting the sun, spherical⁸ in shape, and larger than a certain minimum size.

Here is where the new measurement of the object 2003 UB313 comes in.  A team led by astronomer² Frank Bertoldi of the University of Bonn reports in the journal Nature that it is bigger than the tiny Pluto, which is smaller than Earth's moon. 

The body is too far away to measure by visible means. It has a very elongated⁹ orbit that takes it up to 97 times farther from the Sun than Earth is.  So Bertoldi's team calculated the diameter based on the amount of heat the object emits using a sensitive infrared¹⁰ radiation detector¹¹ on a telescope in Spain.

"The result we have is significant," he said.  "Our best estimate now is 3,000 kilometers.  There is an uncertainty¹² of about 300 to 400 kilometers.  It could be lower, it could be higher, but it makes it definitely larger than Pluto, which has a diameter of 2,300 kilometers."

The finding could be considered a victory for the man who discovered 2003 UB313, Michael Brown of the California Institute of Technology.  He always believed it was bigger than Pluto and maintains that size matters in determining whether something is a planet.

"Pluto has been called a planet for so long that I think we are never going to not call Pluto a planet," he said.  "If Pluto is going to be called a planet, then anything larger than Pluto is a planet.  Things that are smaller I think we just call them typical members of the Kuiper Belt and they do not join this very special class of things that are planets."

The researchers who measured 2003 UB313 agree.  Frank Bertoldi says if it is not considered a planet, it would be increasingly hard to justify¹³ calling Pluto one.

"It is sort of a matter of taste and I guess one has to distinguish between two considerations," he said.  "There is a scientific one and there is a cultural one.  As scientists, we know what we are talking about.  It is not of any consequence whether we call it a planet or not.  Culturally, why not?  Let us call all the objects larger than Pluto that we find out there also planets."

The International Astronomical¹⁴ Union, the discipline's governing body, is debating the issue.  It has formed a committee to define what a planet is. 

Scott Sheppard at the Carnegie Institute says its 20 members are divided, but predicts they are likely to keep Pluto a planet and name the new body one, too.  Yet he is not sure that will settle the issue.

"I think no matter what the International Astronomical Union decides, it will still be a debate for years to come," he said.

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 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。

5 attuned   

v.使协调( attune的过去式和过去分词 )；调音

参考例句：

• She wasn't yet attuned to her baby's needs. 她还没有熟悉她宝宝的需要。
• Women attuned to sensitive men found Vincent Lord attractive. 偏爱敏感男子的女人，觉得文森特·洛德具有魅力。 来自辞典例句

6 domain   

n.(活动等)领域，范围；领地，势力范围

参考例句：

• This information should be in the public domain.这一消息应该为公众所知。
• This question comes into the domain of philosophy.这一问题属于哲学范畴。

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 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 elongated   

v.延长，加长( elongate的过去式和过去分词 )

参考例句：

• Modigliani's women have strangely elongated faces. 莫迪里阿尼画中的妇女都长着奇长无比的脸。
• A piece of rubber can be elongated by streching. 一块橡皮可以拉长。 来自《用法词典》

10 infrared   

adj./n.红外线(的)

参考例句：

• Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
• Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。

11 detector   

n.发觉者，探测器

参考例句：

• The detector is housed in a streamlined cylindrical container.探测器安装在流线型圆柱形容器内。
• Please walk through the metal detector.请走过金属检测器。

12 uncertainty   

n.易变，靠不住，不确知，不确定的事物

参考例句：

• Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
• After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。

13 justify   

vt.证明…正当(或有理)，为…辩护

参考例句：

• He tried to justify his absence with lame excuses.他想用站不住脚的借口为自己的缺席辩解。
• Can you justify your rude behavior to me?你能向我证明你的粗野行为是有道理的吗？

14 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。