James Webb telescopic: the universe is ever out of reach of roses

　　Assembled James WebbTelescope（The configuration (including its "parasol" and modular components) has been partially completed and further installation will take place.

　　Sina science and technology news Beijing time on January 6, according to foreign media reports, NASA's James Webb telescope is currently scheduled for March 2021 launch. Before that, the project has experienced year after year of delays and billions of dollars in funding. Despite the waste of a lot of time and money, but the telescope will become the undoubted "king" of the infrared band, so that we can touch for the first time!UniverseThe remote corners of the world that were once out of reach.

　　From the first galaxies formed after the birth of the universe, to the possibility of extraterrestrial life, the James Webb telescope, costing about $9.7 billion, will be our only hope to further our understanding of everything in the universe.

　　brave the cold

　　Although the James Webb Space Telescope (JWST) is being touted as the "successor" to NASA's legendary Hubble Telescope, it is not. Hubble is primarily an optical telescope, capable of capturing light in a range of wavelengths similar to that of the human eye, expanding only slightly into the infrared and ultraviolet bands. By its very nature, the Hubble telescope is like a giant, orbiting eyeball in space, constantly sending back astounding images. And if your photoreceptor nerves are as strong as its own, you can see these amazing sights for yourself.

　　This is not the case with the James Webb Telescope. It will observe exclusively in the infrared band, barely touching the "reddest" bands visible to the human eye. In other words, it will study a universe that is nearly invisible to humans.

　　One of the main reasons for the design of the James Webb Telescope is the difficulty of carrying out observations in the infrared band from the surface. For astronomers to carry out precise observations and measurements, they must ensure that the night sky is absolutely clear, but light pollution on the ground severely limits the observing conditions.

　　And infrared light pollution is even more ubiquitous because any object with a temperature emits 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 band. Even telescopes themselves emit infrared light radiation at room temperature.

　　In short, it is not that we are completely unable to carry out infrared astronomical observations from the ground, it is just extremely difficult. Therefore, we have chosen to place the James Webb telescope in space.

　　leave home and travel far from home

　　To avoid the effects of infrared light from the Earth, the James Webb telescope will operate 1.5 million kilometers from Earth. Despite being far away from Earth, the sun can be a problem. You must have felt the scorching sunlight outside in the summer - that's infrared radiation. Even at a distance of millions of kilometers from Earth, the sun's heat is still not to be underestimated.

　　There are several options available to designers of infrared space telescopes. One of the most common is the use of active cooling systems to bring the temperature of the telescope down to a level suitable for observing in the infrared band. This is a good approach, and has been used in other infrared space telescopes before. However, it also limits the working life of the telescope, as astronomical observations cannot continue once the coolant is depleted.

　　Therefore, the James Webb telescope will be unique, equipped with an expensive giant "space umbrella". This "umbrella" is 22 meters long and 11 meters wide, made of five layers of highly reflective material, each layer is less thick than the diameter of a human hair. This huge "umbrella" will keep the telescope in the shadows, and the temperature will not exceed -223 degrees Celsius, which is suitable for observation in the target infrared band.

　　However, an instrument mounted on the telescope will be cooled down to minus 258 degrees Celsius with an active cooling system that can pick up infrared light at longer wavelengths.

　　The power of science

　　All in all, the James Webb Telescope is so large that it wouldn't fit on a single rocket. In addition to the huge sunshade, its main mirror diameter of 6.5 meters, far more than the diameter of any rocket currently in use. Since the mirror can not be "glued" on the side of the rocket, the clever NASA engineers decided to divide the mirror into 18 smaller hexagons, so that it can be folded up with the "parasol", as well as the rest of the telescope into the rocket together.

　　Assuming all goes well, a few days after liftoff, the James Webb telescope will fly toward the observing site, deploy the mirror and sunshade into place, and begin its observing mission.

　　And its observations will be extremely surprising. One of the telescope's main observational targets will be the early universe, when the universe was just a few hundred million years old. The first stars and planets that appeared once glowed brightly in the visible wavelengths. But over the past 13 billion years, the universe has gradually expanded, causing the wavelengths of these rays to grow longer and longer, eventually leaving the visible light and falling into the infrared band, which is the ideal observing range for the James Webb telescope.

　　Since the first stars and galaxies to form left no pictures behind, this will be the first time we've observed a view of this important period in the history of the universe.

　　The James Webb Telescope will study everything "cold" in the universe, including protoplanetary disks around primordial stars, molecular clouds, comets, the Kuiper Belt, and more.

　　The telescope will also use a special device to block the light from some of the distant stars, thus capturing any objects that pass in front of these stars, such as exoplanets. These planets appear bright in the infrared band, and the light they emit will allow us to analyze the chemicals and elements in the planets' atmospheres, and perhaps find signs of life in them.

　　In short, from searching for extraterrestrial life, to unraveling the truth of the dawn period of the universe, the James Webb Telescope will surely live up to our years of waiting.