On March 16, local time in the United States, the National Aeronautics and Space Administration (NASA) released a photo of a star taken by the James Webb Space Telescope. The bright ancient galaxy in the background of the image excited scientists. However, the star photos released this time are test photos taken during the telescope debugging process, not official observation photos.
NASA issued a statement on the same day saying that as of March 11, the Webb Telescope has completed 5 of the 7 debugging steps, and the observation results are expected to meet or even exceed the expected goals. It is expected that the commissioning will be completed in early May, and it will be officially “on duty” around the end of June, and the first official observation photo will be released this summer. At that time, the Webb telescope is expected to detect the bright light from the first galaxies when the universe was first formed, and even help human beings to pursue life on alien planets, and its future discoveries are likely to rewrite textbooks again.
Hubble ‘successor’ shoots infrared light in ultra-cold conditions in space
In April 1990, NASA launched the Hubble Space Telescope (hereinafter referred to as the Hubble Telescope) to a distance of 575 kilometers from the ground. Since then, this optical telescope has provided many never-before-seen observations for human astronomy. However, due to its poor initial performance, in December 1993, NASA had to send the space shuttle to repair it.
However, some people in NASA are not optimistic about such maintenance tasks, so they led the establishment of the “Hubble Space Telescope and the Future” committee to evaluate the feasibility of maintenance tasks, and if the maintenance fails, the construction of the next generation of space telescopes. However, the repair operation was successful. The commission’s mission shifted from researching Hubble replacements to researching more advanced space telescopes.
The Hubble Telescope mainly conducts observations in the visible, near-ultraviolet, and near-infrared bands, but many celestial bodies in space have very low temperatures (such as planets or dust disks), and the light radiation emitted by them has a long wavelength and belongs to infrared light. In addition, some ancient objects that can be traced back to the earliest galaxies have a large redshift, and the overall spectrum is also biased towards the infrared. To complete observations of these objects, a cooler and larger telescope is required.
The working temperature of the Hubble Telescope is generally maintained at about 15°C. In order to observe the mid-infrared rays of the design target, the Webb Telescope needs to lower its own temperature to below minus 223°C, that is, use liquid nitrogen or active temperature control to cool the infrared camera. . At the same time, since the Webb telescope also generates heat when it is working, the thermal infrared rays it generates will easily overwhelm the external infrared rays that it wants to observe. Therefore, in order to realize the observation conditions, the scientists covered the Webb telescope with 5 thick “parasols” – polyimide film. Each of these five layers of film is about the size of a tennis court, but only as thick as a human hair. Each layer of film is coated with aluminum on both sides to reflect light and heat. The two layers of film closest to the sunny side are also doped with silicon, which can Heat from the sun is reflected back into space. It should be known that the temperature difference between the two sides facing the deep space and facing the sun exceeds 300°C.
According to the design, the Webb telescope will be placed in the halo orbit on the second Lagrangian point of the earth, and it will make a circular motion around the second Lagrangian point, so the sun, the moon, and the earth will always be in the orbit of the Webb telescope. On the same side, the sunlight reflected from the earth and the moon as well as the infrared radiation from the earth and the moon can be blocked by the 5 layers of sunshade films. Being in this area can also reduce fuel consumption during orbit and maintain communication with NASA’s “Deep Space Network” antenna.
The birth of “Ace Pigeon” cost 10 billion US dollars, and the launch was delayed for more than 10 years
On December 24, 2021, local time in the United States, after spending 10 billion U.S. dollars and continuously “pigeoning” for more than 10 years, the Webb Telescope was finally launched into space.
This is known as an ideal platform for humans to observe the universe in the next 10 years. It was jointly built by NASA, the European Space Agency and the Canadian Space Agency. It started the project in 1997 and started construction in 2004. The launch time was from the original 2007, after many delays. In the end, until December 2021, there were twists and turns such as the rupture of the sunshade film experiment, the delay of the epidemic, and the communication failure of the Star and Arrow. You know, 10 billion US dollars can build more than half of the Ford-class aircraft carrier.
The 6.2-ton Webb Telescope is made up of optical and scientific instruments, a sunshield, and a support system known as the “spacecraft bus.” Among them, the optical module adopts the “three-mirror astigmatism elimination system”: the infrared rays captured by the primary mirror are reflected by the secondary mirror and the tertiary mirror, and then transmitted to the scientific instrument module by the fine steering mirror. The main mirror with a diameter of 6.5 meters is the most eye-catching part of the Webb telescope. It is composed of 18 hexagonal mirrors, and the area of light collected is more than five times that of its “predecessor”, the Hubble telescope. The secondary mirror is supported by three long arms extending from the front of the primary mirror, and the tertiary mirror and fine steering mirror are housed in the raised black “nose cone” in the center of the primary mirror. The materials for the three-stage mirrors are made of metal beryllium, which is not easy to shrink and deform at low temperatures, and the surface of the mirrors is sprayed with 100 nanometers of gold to optimize the infrared reflection performance of the mirrors.
The integrated scientific instrument module is located on the back of the main mirror, including near-infrared cameras, near-infrared spectrometers, near-infrared imagers, seamless spectrometers, and mid-infrared instruments. They will analyze and image the light collected by the Webb telescope. Coupled with the 5-layer “parasol” mentioned above, it constitutes the huge size of the Webb telescope.
Such a huge body can only be put into the fairing of the Ariane 5 rocket in a folded state, and then opened after it is launched into space. The Webb telescope was launched on December 24 last year, and the main mirror was not fully opened until January 8 this year. On January 24, after a month of flight, the Webb telescope reached the second Lagrangian point orbit of the sun-earth system about 1.5 million kilometers above the ground. After more than 10 days of equipment calibration and debugging, NASA announced on February 11 that the Webb Telescope sent back the first batch of space photos, and the subject was a star in the constellation Ursa Major 258 light-years away.
Now, the Webb telescope has sent back another photo of a star. Unlike the 18 images taken by the 18 lenses of the telescope’s main mirror previously sent back, the star image taken this time is an image generated by the unified focusing of 18 lenses.
”You can’t help but look at the thousands of galaxies behind it, it’s so beautiful,” said Jenny Rigby, a scientist working on the Webb telescope project.
“Golden Eye” is tasked with exploring the first stars in the universe 13.5 billion years ago
”The Hubble Space Telescope has revolutionized our understanding of space in many ways,” said Kartik Sheit, deputy science program director for the Webb Space Telescope. “For example, it has provided a lot of information about how galaxies form and evolve. But it is primarily an optical telescope. Although Hubble has several infrared cameras, they are not sensitive enough, and people need to use infrared equipment with higher sensitivity. Due to the expansion of the universe, the light of the first objects reached the telescope, already It is biased towards the red end of the electromagnetic spectrum. The Webb Space Telescope came into being, and it will allow us to see the scene when the universe was very young.”
According to NASA, the Webb telescope will observe the first stars in the universe more than 13.5 billion years ago – How the “first light” was born after the Big Bang and how the first galaxies formed. If the Webb telescope detects the first generation of galaxies, combined with other telescopes’ observations of various galaxies in different periods of the universe, astronomers will be able to study how galaxies grow step by step, thus depicting a complete picture of the evolution of galaxies.