How did the Big Bang happen? How far does the universe really stretch? Are humans alone in the universe?
In the near future, Hubble's successor, the James Webb Space Telescope (JWST), may answer these questions, and now it has handed over the first answers.
JWST has captured the deepest, clearest infrared image of the distant universe to date, and the first full-color image since it entered service.
Using infrared imaging as the eye to observe the unknown ancient universe
Pictured here is the galaxy cluster SMACS 0723, which appeared 4.6 billion years ago and contains thousands of galaxies.
It was taken by JWST's Near-Infrared Camera (NIRCam) and combined with photos of different wavelengths. It took a total of 12.5 hours to collect all the photos, and it would take weeks if it was handed over to Hubble.
▲ Picture from: NASA
On the afternoon of July 11, ET, NASA Administrator Bill Nelson released this photo during a special last-minute briefing at the White House:
Mr. President, if you put a grain of sand at your fingertips an arm's length away, that's part of the universe you see.
But the star clusters in the picture are so large that they even bend space and time around them, resulting in a phenomenon called "gravitational lensing" that magnifies the more distant galaxies behind the cluster.
Light from some of these galaxies has traveled 13 billion years to reach the telescope.
JWST will not only image the celestial object of interest, but it will also split the light into different wavelengths.
As a result, JWST can not only focus on distant nebulae, galaxy clusters and even exoplanets, allowing us to see tiny structures never seen before, but also help researchers understand the mass, age, history and composition of galaxies.
▲ Picture from: NASA
This is mainly because the principle of JWST is different from that of telescopes such as Hubble. It is based on infrared imaging, which observes light from a region of the electromagnetic spectrum (infrared region) that is invisible to the human eye.
The four scientific instruments at play are the Near Infrared Spectrometer (NIRSpec), the Mid Infrared Instrument (MIRI), the Near Infrared Camera (NIRCam), the Near Infrared Imager and the Seamless Spectrograph (NIRISS).
Hubble has some infrared detection capabilities, but not as well as JWST.
▲ Hubble observes the visible light (left) and infrared view (right) of the Hericium Nebula. Image credit: NASA and ESA
The infrared region observed by JWST is crucial for charting the timeline of our universe – as the universe continues to expand, the oldest and rarest stars, and the things illuminated by them, only appear to us as infrared light .
Astronomers hope to use JWST to explore every stage of cosmic history, from the interior of our solar system to the most distant observable galaxies in the early universe, and everything in between, helping humanity understand the origin of the universe, galaxy evolution and our position in it.
That said, we can expect to observe the early state of the visible universe today, seeing the first galaxies formed just a few hundred million years after the Big Bang, revolutionizing astrophysics as we know it.
This photo is just a preview. At 22:30 on July 12, Beijing time, NASA will broadcast live broadcasts of more full-color images and data , including nebulae, galaxies, and atmospheres of extrasolar planets.
The most expensive space telescope to date, with no room for error
JWST launched on December 25, 2021, after about 25 years of development.
Before that, it went through decades of preparation, with plans beginning in the early 1990s, named after NASA's second administrator, James Webb, with a budget of $500 million, and it became operational in 2007 .
However, the difficulty of building the JWST far exceeded NASA's expectations. Due to many engineering delays and cost overruns on the project, the JWST underwent a major redesign in 2005, and the launch time was delayed until the JWST finally had a launch in 2021. may launch.
25 years of continuous investment from 20 countries, the cooperation of tens of thousands of scientists, various setbacks and multiple delays, various factors have created the most expensive space telescope in history, and the cost of JWST is close to 10 billion US dollars .
▲ Fully expanded JWST (art rendering). Image credit: NASA
Cutting-edge science burns money, and naturally there is a reason to burn money. It includes larger-caliber lenses, 10-nanometer-level mirror materials, sun visors the size of a tennis court, etc. ", must be 100% correct.
In short, technology is breakthrough, R&D is all-or-nothing, and it is not a simple linear increase in cost.
Even if it can be launched, the JWST is too large to be launched directly into space in its complete form. It must be folded to be installed on a rocket for launch. It can only complete various adjustments in distant space after launch, and no mistakes are allowed.
It took two weeks just to deploy the visor in space.
The temperature of the JWST observation module must be kept below 40K (-233.15°C) in order to see weak infrared light, and the sun visor plays the role of temperature control. Otherwise, the target's signal would be drowned out in infrared radiation from the telescope itself, the sun, the Earth and the moon.
▲ The sun visor was tested on the ground before launch. Image credit: NASA
The complexity of unfolding the visor is that each joint must be executed perfectly for the visor to be opened. The entire JWST has as many as 344 single points of failure, and the visor contains a significant portion of them, and a single point of failure means that once a failure occurs, the entire project fails. Accidental tearing of the film during testing in 2018 was also one of the factors that delayed the project.
The calibration of the primary mirror is also time-consuming.
The JWST's primary mirror, designed as a "honeycomb" foldable mirror consisting of 18 hexagonal mirrors, helps it capture a large amount of infrared light from a chosen target. But each of these mirrors (plus secondary mirrors and other components) needs to be precisely adjusted so that the image reflected in them matches and overlaps with the other mirrors.
▲ Animated from: [email protected]
For the past six months, engineers and scientists have been carefully adjusting the mirror portion of the telescope and calibrating its instruments.
Now, JWST is finally ready to start collecting light from distant galaxies for humanity.
#Welcome to pay attention to the official WeChat account of Aifaner: Aifaner (WeChat: ifanr), more exciting content will be brought to you as soon as possible.