The James Webb Space Telescope (JWST), a thirty-year-long wait by astronomers around the world to probe the universe with unique instruments, reached its observation post on Saturday thanks to the Ariane 5 rocket, 1.5 million km from Earth. Going to do.

After take-off from the Guiana Space Center, scheduled for a 32-minute window from 12:20 GMT, JWST will become the most advanced cosmic observation instrument ever flown into space.

With the ambition to shed more light on humanity on the two questions that torment it: “Where do we come from?” “and” are we alone in the universe? ,

And thus catch a glimpse of the “cosmic dawn,” when the first galaxies began to illuminate the universe since the Big Bang 13.8 billion years ago.

This will make it possible to better understand the formation of stars and galaxies, and observe those exoplanets, of which astronomers are discovering more and more samples, perhaps one day to identify other Earths.

James Webb would follow in the footsteps of the Hubble Telescope, which revolutionized the observation of the universe: it was thanks to him that scientists discovered the existence of a galactic black hole at the center of all galaxies, or the water vapor surrounding exoplanets.

– See the first galaxy –

Conceived by NASA since the launch of Hubble in 1990, and built in collaboration with European (ESA) and Canadian (CSA) space agencies since 2004, JWST differs in more ways than one.

The size of its mirror, with a wingspan of 6.5 meters, gives it a surface area and therefore sensitivity seven times higher, enough to detect the thermal signature of a bumblebee on the Moon.

Another difference: the way of observing it. Where Hubble primarily observes space in the region of visible light, James Webb ventures into a wavelength that strikes the eye: near- and mid-infrared. A radiation that any body, star, human or flower, emits naturally.

This light will be studied by four instruments equipped with imagers and spectrographs to better dissect it. Their development mobilized a large number of engineers and scientists from American and European laboratories and led by industrialists.

Thanks to this “by looking at similar objects (with Hubble), we will see new things”, explained astronomer Pierre Ferruit in Paris, scientific co-head of the telescope for ESA. For example the first galaxy, objects whose distance caused their light to turn red. Or young colonies of stars, hidden in the dust clouds of their nurseries. Or the atmosphere of an exoplanet.

The prerequisite for the proper functioning of the JWST is an ambient temperature low enough that it does not interfere with the test of light.

The Hubble orbit is about 600 km above Earth. At this distance, the JWST would be unusable, heated by the Sun and its reflection on Earth and the Moon. It will be placed at the end of a month’s journey 1.5 million km away. and will be protected from solar radiation by a thermal shield of five flexible sails that will dissipate heat, reducing the temperature on the side of the telescope (which is 80°) to -233°.

– Avoid pollution-

But before getting there, the machine and its designers must achieve a real feat: its flawless deployment, which includes a series of operations, for example, for shields alone, 140 opening mechanisms, 400 pulleys and nearly 400 meters of cable. . ,

Because the observatory, which has a slope of 12 meters high and equal to that of a tennis court, had to be folded to slip into Ariane 5’s cap. The equipment was “encapsulated” with laser guidance to avoid any damage, a development that cost about ten billion dollars.

For these maneuvers, NASA also implemented stringent hygiene measures to prevent any contamination of the telescope’s mirror particles or charged breath…

Finally, a tailor-made fairing depressurization system was installed by Arianespace, so that when it is detached from the launcher at an altitude of 120 km, any sudden pressure changes will not harm the animal. “A + customer + exceptional, extraordinary measure”, explained an ESA official in Kourou on Thursday.

We will know after 27 minutes whether the proposed phase of flight went well or not. This would further seal the collaboration between NASA and its European partners. For space, “strong collaboration is essential to accomplishing great things,” ESA and NASA officials told Kourou.

However, it will take several weeks to know whether the telescope is ready for use. With official entry into service scheduled for June.