After nearly two decades of development (or three, counting the initial proposals) and seven years of delay, the James Webb Space Telescope is expected to go into space on the 25th, at around 9:20 am (GMT).
The promise is to revolutionize our understanding of the Universe and bring us closer to the answer to the classic question “Are we alone?” But that’s only after a dramatic month of activity to get the telescope into operation. There is no margin for error.
The NASA (American space agency) project, conceived in partnership with ESA (its European counterpart) and CSA (Canadian), had its formal beginning in 2003, based on proposals that date back to the 1990s, not long after of the launch of the Hubble Space Telescope.
It is not by chance that the project has since been presented as “the successor to Hubble”, although it is important to qualify how this succession takes place.
One of the great creators of the project was John Mather, an astrophysicist at NASA’s Goddard Space Flight Center. Winner of the 2006 Nobel Prize in Physics, Mather was one of those responsible for the Cobe satellite, which operated from 1989 to 1993 and mapped the small variations in the cosmic background radiation, the microwave echo left by the Big Bang.
It is, in essence, the first light to circulate freely in the Universe, when it was only about 380,000 years old, and it shows the small fluctuations in the distribution of matter and energy that would ultimately produce stars and galaxies.
Hubble, launched in 1990, was used to probe the depths of the Universe, reconstructing the last 13 billion years of cosmic history. The further away the observed object, the older it is (because the time it takes for light to reach us, traveling through a vacuum at 300,000 km/sec, is greater).
With this, the venerable space telescope, still in operation today, managed to see some of the first galaxies of modern configuration to appear in the Universe, some 500 million years after the Big Bang. But when Hubble tries to see further than that (and farther back in time), all it finds is darkness. Not because there’s nothing there, but because the light that comes from farther away is invisible to him.
Webb, in turn, was designed to see what Hubble can’t. It is hoped that he can delve into this journey into the past and see the first primitive galaxies, diving into a period up to 300 million years after the Big Bang, who knows less.
With this, it will reveal whether our current cosmological models really stand still, which indicate how the Universe evolved since the beginning, 13.8 billion years ago, and fill in the gaps between what we have already observed directly in the cosmic background radiation. and in the Hubble observations.
“We have the movies that show what the computer thinks must have happened if this story [o modelo cosmológico padrão] is just right,” says Mather. “And now we want to check it out by looking at everything we can. We want to see those first galaxies grow.”
“Redshift”
Hubble was the first large space telescope in history and focused mainly on observing around the light that the human eye can see: the so-called visible spectrum. The observatory could also see some ultraviolet, which has shorter wavelengths, and infrared, which has longer wavelengths.
This explains why everything becomes invisible as Hubble tries to see further. Light traveling great cosmic distances passes through space that is itself expanding (this has been happening since the Big Bang, space itself is growing).
When a wave of light passes through expanding space, it is also stretched, what astronomers call “redshift”, or “redshift”. In practice, this means that the light wave that was born visible or even ultraviolet in the back of the cosmos, when traveling to us, stretched out, increasing its wavelength and turning red, until it turned infrared.
For that reason, Webb is both a successor to Hubble (aimed at seeing farther) and an entirely different telescope (focused on light Hubble could never see): it will only pick up infrared light.
This means that when you see an image of him posted out there, you will be seeing a “translation” into visible light of things that the human eye cannot see. And with that we will delve deeper than ever into the cosmic past. Sure, if all goes well.
30 days of terror
The launch is just the beginning of a long journey to a point about 1.5 million km from Earth. Powered by an Ariane 5 rocket, provided by ESA, the Webb goes into space all folded in on itself. Until it reaches its final orbit, an intricate opening and unfolding process will unfold so that the telescope can be effectively used.
It’s no joke. Those involved have already dubbed the process “30 days of terror”, emulating the landings on Mars, which involve the “7 minutes of terror”, in which the spacecraft must successfully cross the Martian atmosphere, in a fully automated way. In the case of Webb, there are more than 300 individual elements that need to work right, at the right time, for the mission to be successful.
Just comparing the telescope’s images in its operational configuration and in the folded version, inside the rocket’s hood, it is already possible to extract some of these steps.
The heat shield—a sort of five-layer folding awning that goes under the main mirror and is comparable in size to a tennis court—needs to open correctly, as well as two side segments of the segmented main mirror and the secondary mirror frame.
But the details make everything even more tense. Example: To separate the five layers of the heat shield, you need to detonate 107 screws that secure them in the launch configuration. If a single one of these screws fails to fire, the project is doomed.
It is unprecedented complexity in the largest space telescope ever launched by mankind. Compare Webb’s 6.58 meter main mirror to Hubble’s, at (now) a modest 2.4 meters.
Technological challenges scale in the same proportion. With the added drama that Hubble was designed to orbit the Earth some 550 km above the surface, where it could be visited by astronauts on old space shuttles for repairs and upgrades. The Webb will not have that luxury, installed 1.5 million km from the nearest mechanics. Nothing can go wrong.
This helps to explain the huge overruns in the budget, accompanied by repeated delays. When the project started in 2003, it was expected to launch it in 2014 at a cost of US$5 billion (R$28.4 billion at the current price). Since then, the price tag has risen to more than US$10 billion (R$56.8 billion). As for the launch, now it goes.
From the solar system to the depths
The delays ended up raising expectations. Originally designed to take this deep dive into the Universe’s past, it now proves to be much more versatile.
With its spectrographs, it will be able to probe the atmosphere of Earth-sized exoplanets that are in the habitable zone of nearby stars (the Trappist-1 system, 40 light-years away, is already in the queue for the first observations).
It is not inconceivable that he discovers that these worlds are actually habitable and, if we are very lucky, even inhabited (life, on Earth at least, has the habit of radically transforming the atmosphere, which in theory could also be identified in these exoplanets) .
In 2003, when the project began, no one knew of Earth-sized planets in the habitable zone of any star, let alone design a telescope to study their atmospheres.
After all, it’s a general purpose telescope. Like Hubble, it should revolutionize all areas of astronomy, from the study of bodies in our Solar System to the farthest depths of the cosmos. And, of course, the best discoveries will be those that we cannot even imagine today.
It’s an exploration mission, above all. It starts on launch day, will go through 30 days of terror until it reaches operational status and then we’ll have six months of instrument calibration and commissioning before the first scientific observations begin. But for those who have waited nearly two decades, there is very little left now.
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