Beijing time on January 6, according to foreign media reports, NASA's James Webb telescope is currently scheduled to launch in March 2021. Prior to that, the project experienced a year-over-year delay and billions of dollars in capital investment. Although a lot of time and money was wasted, this telescope will become an unquestionable "king" in the infrared band, allowing us to reach the remote corners of the universe that were once out of reach for the first time.
From the first galaxies formed after the birth of the universe to the possibility of the existence of extraterrestrial life, to further understand the universe, the James Webb telescope, which spends about $ 9.7 billion, will be our only hope.
Not afraid of the cold
Although the James Webb Space Telescope (JWST) is considered the "successor" to NASA's legendary Hubble Telescope, this is not the case. Hubble is mainly an optical telescope. The wavelength range of light it can capture is similar to that of the human eye, only slightly expanding to the infrared and ultraviolet bands. By its very nature, the Hubble Telescope is like a huge eyeball orbiting in space, constantly returning shocking pictures. And if your light sensory nerve is as powerful as it is, you can see these amazing sights yourself.
Not so with the James Webb telescope. It will observe completely in the infrared band, and will hardly touch the most "red" band that human eyes can see. In other words, it will study a universe that is almost invisible to humans.
One of the main reasons why the James Webb telescope is designed this way is that it is very difficult to carry out infrared band observations from the surface. For astronomers to make accurate observations and measurements, they must ensure that the night sky is absolutely clear, but light pollution on the ground severely limits observation conditions.
And infrared light pollution is ubiquitous, because any object with temperature will emit infrared light. The human body can produce 100 watts of infrared radiation. The earth itself is also very hot, and appears bright in the infrared. Even the telescope itself emits infrared light radiation at room temperature.
In short, we are not completely unable to carry out infrared astronomical observations from the ground, but it is extremely difficult. Therefore, we chose to place the James Webb telescope in space.
Away from home
To avoid the effects of Earth's infrared light, the James Webb telescope will operate at a distance of 1.5 million kilometers from Earth. Although far away from the earth, the sun is also a problem. You must have experienced the scorching sun outside in summer, and that is infrared radiation. Even millions of kilometers away from the earth, the heat of the sun cannot be underestimated.
To this end, designers of infrared space telescopes can take several countermeasures. The most common one is to use an active cooling system to reduce the temperature of the telescope to a level suitable for observation in the infrared band. This is a good method, and it has been adopted in other infrared space telescopes before. But this also limits the working life of the telescope, because astronomical observations cannot continue once the coolant is depleted.
As a result, the James Webb telescope will take its own path, equipped with an expensive giant "space umbrella". The "umbrella" is 22 meters long and 11 meters wide, and is made of five layers of highly reflective material, each layer less than the diameter of a human hair. This huge "sunshade" will keep the telescope in the shadow and the temperature does not exceed minus 223 degrees Celsius, which is suitable for observation in the infrared band of the target.
However, an instrument mounted on the telescope will use an active cooling system to cool it to minus 258 degrees Celsius and can receive longer-wavelength infrared light.
The power of science
All in all, the James Webb telescope is so bulky that it can't fit in a single rocket. In addition to that huge parasol, its main mirror has a diameter of 6.5 meters, which is far beyond the diameter of any rocket currently in use. Since the mirror cannot be "sticked" to the side of the rocket, the smart NASA engineers decided to divide the mirror into 18 smaller hexagons so that it can be stuffed with the folded "sun umbrella" and the rest of the telescope Inside the rocket.
If all goes well, a few days after the launch of the James Webb telescope, it will fly towards the observation point, unfold the mirror and parasol, and then start the observation mission.
And its observations will be extremely amazing. One of the telescope's main observation targets will be the early universe, just a few hundred million years after the universe was born. The first stars and planets that appeared appeared to be dazzling in visible light. But over the past 13 billion years, the universe has gradually expanded, causing the wavelengths of these rays to become longer and longer, and finally leave visible light and fall into the infrared light band, which is exactly the ideal observation range of the James Webb telescope.
Since there were no pictures left of the first stars and galaxies formed, this will be the first time we have observed this important period in the history of the universe.
The James Webb Telescope will study all "icy" objects in the universe, including protoplanetary disks, molecular clouds, comets, Kuiper belts, etc. around nascent stars.
The telescope will also use a special device to block light from some distant stars, thereby capturing any celestial bodies passing in front of these stars, such as exoplanets. These planets appear very bright in the infrared band. Through the light they emit, we can analyze the chemicals and elements in the planet's atmosphere, and maybe find signs of life from them.
In short, from searching for extraterrestrial life to revealing the truth of the dawn of the universe, the James Webb telescope will certainly live up to our many years of waiting.