Explainer: Comparing Two Space Telescopes

 

On December 25, the new James Webb Space Telescope launched into space from South America on a European Ariane 5 rocket.

"[countdown from 10 in French, continued in English] Lift off! From a tropical rainforest to the edge of time itself, James Webb begins a voyage back to the birth of the universe."

NASA and the European Space Agency's Hubble telescope has been circling the Earth for nearly 32 years. Webb is widely seen as the next generation telescope.

Experts recently spoke¹ with The Associated Press about the differences between the two telescopes. But when talking with scientists of astronomy, do not ask them to pick a favorite.

"Comparing Hubble and Webb is like asking if you love your second child as much as your first," said Susan Mullally. She is Webb's assistant project scientist at the Space Telescope Science Institute in Baltimore, Maryland in the United States.

"Hubble will always be loved for its awe²-inspiring images of our universe and will continue to collect important data for astronomers³." But the Webb telescope, Mullally adds, will permit us to see places in the universe never before seen. The Webb telescope is bigger and 100 times more powerful than Hubble.

In 1990, the Hubble caught a ride to its orbit inside NASA's space shuttle Discovery. For Webb, the NASA website explains that it was helpful for the launch to be near the equator because "...the spin of the Earth can help give an additional push."

Location and problems in space

Hubble circles 530 kilometers overhead. That distance was determined⁵ by the abilities of NASA's space shuttles. When problems happened on Hubble, ground control specialists and astronauts were able to fix them.

However, this will not be the case with Webb. Webb is heading to a much more distant spot -- 1.6 million kilometers away. If it runs into problems, it will be on its own.

All the light we see

Webb is expected to record light from the universe's first stars and galaxies⁶. This is beyond the abilities of Hubble. This light will show us how the original stars looked 13.7 billion years ago.

Hubble has looked back as far as 13.4 billion years. Astronomers want to close that 300 million year hole with Webb. This will come ever closer in time to the Big Bang, the moment the universe formed 13.8 billion years ago.

Infrared⁷ vision

Hubble sees what we see — visible light.

Webb has infrared vision, so it can see light that is invisible to the Hubble. It can see through clouds of space dust. The shorter visible and ultraviolet light given off by the first stars and galaxies have been stretched as the universe grows. So, Webb will see them in their infrared form, which is stretched out and giving off heat.

Webb's detectors⁸ need to run at minus 240 degrees Celsius¹⁰. To stay this cold, Webb carries an "umbrella" the size of a tennis court. Between each of the sunshield's five layers is a hole so heat can escape out the sides.

Larger mirror

To see the universe's first stars, Webb needs the largest mirror ever launched for astronomy.

The Webb mirror is more than 6.5 meters. Hubble's is 2.4 meters across. However, Webb's mirror is lighter¹¹ because it is made of beryllium, a strong but lightweight metal.

Production and costs

The Hubble and Webb do have things in common: Production of both were years late and overbudget.

NASA's cost for Hubble from its 1970s development until now is about $16 billion, adjusted for inflation. That does not include all the shuttle flights for launch and repairs.

Webb's price tag is an estimated $10 billion. That includes the first five years of operation. The European Space Agency is paying for the launch costs.

Words in This Story

tropical – adj. of or occurring in the tropics

astronomy – n. the scientific study of stars, planets, and other objects in outer space : astronomer⁴ – n. a person who is a specialist in astronomy

awe-inspiring – adj. that arouses awe or wonder

spin – v. to turn or cause someone or something to turn around repeatedly

galaxy¹² – n. any of the very large groups of stars and associated matter that are found throughout the universe

infrared – adj. producing or using rays of light that cannot be seen and that are longer than rays that produce red light

vision – n. the act or power of seeing

ultraviolet – adj. used to describe rays of light that cannot be seen and that are slightly shorter than the rays of violet light

detector⁹ – n. a device that can tell if a substance or object is present

mirror – n. a piece of glass that reflects images

1 spoke   

n.（车轮的）辐条；轮辐；破坏某人的计划；阻挠某人的行动 v.讲，谈（speak的过去式）；说；演说；从某种观点来说

参考例句：

• They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
• The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。

2 awe   

n.敬畏，惊惧；vt.使敬畏，使惊惧

参考例句：

• The sight filled us with awe.这景色使我们大为惊叹。
• The approaching tornado struck awe in our hearts.正在逼近的龙卷风使我们惊恐万分。

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 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。

5 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

6 galaxies   

星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）

参考例句：

• Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。

7 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。

8 detectors   

探测器( detector的名词复数 )

参考例句：

• The report advocated that all buildings be fitted with smoke detectors. 报告主张所有的建筑物都应安装烟火探测器。
• This is heady wine for experimenters using these neutrino detectors. 对于使用中微子探测器的实验工作者，这是令人兴奋的美酒。 来自英汉非文学 - 科技

9 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。

10 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

11 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

12 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。