Among the more than 8,000 man-made flying objects floating above us, the Hubble Telescope is probably the most legendary and well-known one.
The idea of the Hubble Telescope can be traced back to 1946. Astronomer Lyman Spitzer proposed that an observatory built in space can observe more infrared and ultraviolet rays absorbed by the atmosphere, and the observation limit is higher.
After nearly half a century of design and manufacturing, the Hubble Telescope was finally put into orbit 600 kilometers from the ground by the Space Shuttle Discovery on April 24, 1990, and it has been in operation ever since.
▲"The Pillars of Creation", one of the most famous photos taken by Hubble Telescope
In the past 31 years, more than 17,000 papers have been produced based on the information based on Hubble observations. From dark energy to outer planets to black holes, Hubble has helped astronomers unlock the secrets of the universe one after another, acting as the eyes of human beings. character of.
Since its service, the Hubble Telescope has undergone 5 manual maintenance, and there are countless large and small software failures.
In June of this year, the Hubble Telescope was suspended due to a system failure and switched to the backup system; on October 26, the Hubble Telescope entered a safe mode due to internal communication problems.
How long can this "Eye in Space", which was originally planned to work until 2013, last? Astronomers are not yet able to give a definite answer, but what is certain is that the elderly Hubble is about to rest.
In order to see a broader universe, scientists believe that it is necessary to find a "successor" for Hubble as soon as possible.
Where is the next "earth"?
Is there any other life in the universe? Where is the next planet suitable for human habitation? These questions I read in "One Hundred Thousand Whys" when I was a child, the scientific community has not yet found the answer.
The good news is that these issues are likely to be the focus of NASA's astronomy work in the next 10 years.
The National Academy of Sciences, Engineering, and Medical Sciences released a survey report titled "Astronomy and Astrophysics Decade 2020 Survey" (Astro2020) last week, which mentioned three major research themes to be prioritized by American astronomy in the next 10 years They are: searching for possible habitable exoplanets, understanding the mysteries of black holes and neutron stars, and studying the formation and evolution of galaxies.
Relying on existing observation equipment, it is not easy to achieve these goals. For example, when looking for potentially habitable exoplanets, because nearby stars are usually tens of billions of times brighter than planets, faint planets are easily obscured by their light. , Affect the observation.
Therefore, in order to accomplish such a grand research goal, the first task of astronomers is to "upgrade equipment." This is also one of Astro2020's key plans-to build a new giant telescope that surpasses the Hubble Telescope.
The plan mentions that NASA will fund and build a new telescope that is much larger than the Hubble telescope and is equipped with ultraviolet, visible and infrared detectors at the same time. It is estimated to cost 11 billion U.S. dollars. Ideally, it will be invested in the early 1940s. use.
The new telescope will be equipped with coronagraphs and other equipment, so that when observing exoplanets, it can effectively reduce the light interference of nearby stars for further observation.
In an interview with Axios, chief scientist John O'Meara of Keck Observatory briefly introduced this grand planetary exploration program.
In the next 10 years, scientists need to search for 100 or more sun-like stars and screen out potentially habitable planets based on the orbits of the planets around them.
Next, astronomers performed spectral analysis on the 25 most likely planets to study their atmospheric composition and whether there were signs of life.
The new type of telescope will play an important role at this time. Through the light reflected by the exoplanet, scientists can calculate the chemical composition of its atmosphere. If there are components such as oxygen, methane, and water in the atmosphere, then this planet is likely to be able to breed life.
"When we see the first signs of life in the universe other than humans, and see the traces of life in the distant world, the position of humans in the universe will fundamentally change," John O'Meara emphasized in an interview.
On the other hand, he also added that if humans observe 25, 50 or even 100 exoplanets without any discovery, this will also fundamentally change the view of the universe.
Since this observation task requires the collaborative analysis of multiple spectra including ultraviolet, visible, and infrared, it is very necessary to build a new large telescope. However, judging from various past experiences, there is a high probability that this new space exploration program will not be smooth sailing.
Building the second "Hubble" is not easy
▲ Compton Gamma-ray Telescope
Between 1990 and 2003, NASA successfully developed and launched 4 large space telescopes, namely the Hubble Space Telescope, the Compton Gamma-ray Telescope (which crashed in 2000), the Chandra X-ray Telescope and the Spey Strategic Space Telescope, which is also known as the large-scale orbital observatory program.
▲ Chandra X-ray telescope
The large-scale orbital observatory project has advanced astronomy research into an era. Because infrared, X-ray and gamma rays have difficulty penetrating the Earth’s atmosphere, observations can only be made through space telescopes located in space, and each telescope is dedicated to its own field. Made an important contribution.
In 1996, NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA) began to cooperate in the development of the next generation of space telescopes, named after NASA’s second director James Webb, with a budget of 500 million US dollars, planned for 2007 Put into use.
However, the difficulty of constructing the James Webb Space Telescope (JWST) far exceeded NASA’s expectations. Due to the project’s many engineering delays and cost overruns, JWST underwent a major redesign in 2005, and the launch time was delayed. , Until 2021 JWST is finally possible to launch.
The JWST, originally scheduled to be launched on October 31, 2021, was postponed to December 18, 2021 due to problems with the Ariane 5 launch vehicle. If there is no accident, one month later, the 24-year major The project will usher in a historic breakthrough.
JWST is often regarded by the outside world as the successor of Hubble, but the work of the two is actually not exactly the same. The main task of JWST is to observe the residual infrared rays of the Big Bang theory, that is, to observe the state of the early universe, so its shape and working environment are very different from those of the Hubble Telescope.
The first is altitude. Compared with the 600 km orbital height of the Hubble Telescope, JWST is much farther, 374,000 km when it is closest to the earth (near arch point), and can reach 150 million km when it is farthest (far arch point).
This is because the lens of JWST must be kept below 50K (−220 °C). In order to maintain the low temperature, JWST has designed 5 layers of hoods that can withstand about 300 °C to block the light reflected by the sun and the earth. .
From the appearance point of view, JWST is almost composed of this huge lens and hood. Its main mirror has a diameter of 8 meters, and the mirror area is more than 5 times that of the Hubble Telescope, while the area of the sunshade is equivalent to a tennis court.
It is a huge problem to allow such a huge structure to be released and unfolded accurately and safely in space. NASA engineer Mike Menzel mentioned in the press conference that the deployment of the JWST solar shield will be the most complicated deployment task, with more than 300 possible failures.
According to statistics, JWST estimates that it will cost up to 9.66 billion U.S. dollars, far exceeding the planned budget. Many astronomers worry that due to the long delay of JWST and serious over-budget, new telescope construction may be difficult to obtain funding support.
But from another point of view, the troubled JWST also left a lot of valuable development experience.
In the Astro2020 report, a lot of JWST development lessons were summarized, and four more detailed mission concepts were put forward. The development plan of the new telescope is more complete than the original JWST.
If the plan is carried out smoothly, mankind's understanding of the universe will usher in another leap. Does alien life exist in the universe? The answer to this question is likely to be revealed within this century.
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