US Astronomers Find 'Smaller' Planets Around Distant Suns

By David McAlary

U.S. astronomers¹ have made a finding they say increases the chance that distant stars may harbor planetary systems like our own. They have discovered two planets the size of Neptune² elsewhere in our galaxy³. These are the smallest planets yet found outside our solar system and may herald⁴ the discovery of even smaller ones like Earth.
Two teams of astronomers working separately found the two planets the same way most of the other 130 have been found in the past nine years. They did not see them directly, but measured the magnitude of the wobble the planets' gravity induces in their nearby stars.
The importance is that these two caused a smaller wobble in their stars than all the rest, leading the astronomers to conclude the planets are smaller. Previously⁵ detected planets have masses roughly the same as our solar system giants Jupiter and Saturn⁶. The two new ones are estimated at roughly 20 times less mass, about that of Neptune, and only two to three times the diameter of Earth.
The findings are further evidence that planets and diversified⁷ solar systems are not rare in our galaxy and the universe beyond. One of the new planets circles a kind of star that is the most abundant to our galaxy, a so-called M class star. The planet's co-discoverer is Geoffrey Marcy of the University of California at Berkeley.
"As a result of this planet and one other around these M class stars, we estimate that something like 20 billion planetary systems exist within our Milky⁸ Way galaxy alone," he said.
The other new planet is in a system with three companion planets the mass of Jupiter, the first known multi-planet combination outside our solar system.
"It is quite a remarkable⁹ discovery," he noted¹⁰. "Obviously, we're edging closer and closer to planetary systems that have a full complement¹¹ like the nine planets that go around our Sun."
The researchers say they do not know the composition of the two new Neptunes, but if they are like our Neptune, it is a combination a rock and ice. Mr. Marcy's colleague, Paul Butler of the Carnegie Institution in Washington, DC, says this is a transition stage between giant gas planets the mass of Jupiter and Saturn and smaller, rocky planets like Earth and Mars, an intermediate stage that is probably found elsewhere.
"So this puts us a step closer. It puts us in that transition region where we can't quite see the Earth-like planets yet, but we are seeing their big brothers, and hopefully we will be bearing down on these smaller mass planets soon," said Mr. Butler.
The scientists say they expect that improvements in technology and search methods will lead them to Earth-size planets well within a decade.
The U.S. space agency's chief of astronomy, Anne Kinney, says the planet findings that have occurred so far reflect astounding¹² progress since the first was detected outside our solar system in 1995.
"Ten years ago, this field barely existed. I myself never dreamed that we would be making announcements about Neptune class planets at this stage," said Ms. Kinney.
David McAlary, VOA News, Washington.

注释：
planetary 行星的
Neptune 海王星
galaxy 星系
magnitude 大小
wobble 摇晃，不稳定
gravity 重力
Jupiter 木星
diameter 直径
diversified 多变化的
Berkeley 伯克利
Carnegie Institution in Washington DC 卡耐基华盛顿研究所

1 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》

2 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。

3 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。

4 herald   

vt.预示...的来临，预告，宣布，欢迎

参考例句：

• In England, the cuckoo is the herald of spring.在英国杜鹃鸟是报春的使者。
• Dawn is the herald of day.曙光是白昼的先驱。

5 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

6 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。

7 diversified   

adj.多样化的，多种经营的v.使多样化，多样化( diversify的过去式和过去分词 )；进入新的商业领域

参考例句：

• The college biology department has diversified by adding new courses in biotechnology. 该学院生物系通过增加生物技术方面的新课程而变得多样化。 来自《简明英汉词典》
• Take grain as the key link, develop a diversified economy and ensure an all-round development. 以粮为纲，多种经营，全面发展。 来自《现代汉英综合大词典》

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 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

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 complement   

n.补足物，船上的定员；补语；vt.补充，补足

参考例句：

• The two suggestions complement each other.这两条建议相互补充。
• They oppose each other also complement each other.它们相辅相成。

12 astounding   

adj.使人震惊的vt.使震惊，使大吃一惊astound的现在分词)

参考例句：

• There was an astounding 20% increase in sales. 销售量惊人地增加了20%。
• The Chairman's remarks were so astounding that the audience listened to him with bated breath. 主席说的话令人吃惊，所以听众都屏息听他说。 来自《简明英汉词典》