US Spacecraft Flies by Pluto After Nine-Year Trip

AS IT IS 2015-07-15 US Spacecraft Flies by Pluto¹ After Nine-Year Trip

It has taken more than nine years for an American spacecraft to reach the far edge of our solar system. The spacecraft, named New Horizons, sailed past the “dwarf²” planet Pluto on Tuesday. New Horizons flew 4.88 billion kilometers to reach Pluto.

The spacecraft completed the fly-by Tuesday morning, after reaching an area called the Kuiper Belt, which lies outside the planet Neptune³. This success tops off a 50-year effort by scientists to explore our solar system.

“It’s truly a mark in human history,” said John Grunsfeld. He is the associate administrator⁴ for science at NASA, the American space agency. He is with the mission control center at Johns Hopkins University’s Applied⁵ Physics Laboratory.

The spacecraft is so far from Earth, that radio signals, traveling at the speed of light, take about four-and-a-half hours to reach scientists on our planet. More information is expected to arrive Tuesday night. That is when New Horizons is expected to send final word that it has passed some 12,550 kilometers from Pluto.

“We will get information from the spacecraft and know if it’s healthy,” said Alice Bowman, the mission operations manager.

By that time, New Horizons will have spent almost a day in radio silence. It has been quiet while it works on a series of observations as it flies past Pluto and its five moons. New Horizons is traveling at speeds of about 14 kilometers per second.

The spacecraft is about the size of a baby grand piano. It is fueled by nuclear power. For several hours after the closest pass by Pluto, New Horizons will look back at the planet. It will study its atmosphere using radio signals sent from Earth as a probe. New Horizons does not have the ability to fire rockets to slow down and go into orbit around Pluto. So its cameras and scientific instruments must work on the fly, without slowing down.

Scientists want to know more about Pluto. When New Horizons was launched in 2006, Pluto was considered our solar system’s ninth planet. But since then scientists decided⁶ it was a “dwarf planet” after other Pluto-like ice and rock worlds were discovered in the Kuiper Belt.

Those objects are believed to be left over pieces from the creation of the solar system some 4.6 billion years ago. Scientists will have to be patient to wait to receive all of New Horizons’ information. It will take about 16 months for the spacecraft to send back all the images and other data taken during the Pluto fly-by. By then, it will have traveled even deeper into the Kuiper Belt. There it may be heading for a possible visit with one of Pluto’s neighbors.

Words in This Story

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

dwarf – adj. something of relatively⁷ small size

probe –n. an instrument that is used for examining something

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 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。

3 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。

4 administrator   

n.经营管理者，行政官员

参考例句：

• The role of administrator absorbed much of Ben's energy.行政职务耗掉本很多精力。
• He has proved himself capable as administrator.他表现出管理才能。

5 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

6 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。

7 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。