The successful take-off Saturday, December 25 for the James Webb Space Telescope, has been awaited for thirty years by astronomers around the world to probe the universe with unique instruments. The telescope will be able to reach its observation post 1.5 million km away from Earth.

The James Webb, the most powerful space telescope ever built, hit the ground with an Ariane 5 rocket at 12:20 GMT from the Guyana Space Center. Exactly 27 minutes and seven seconds later, Director of Launch Operations Jean-Luc Voire announced: “Good Separation Webb telescope, go Webb”, to applause at the Jupiter Control Center in Kourou.

“It’s a real Christmas gift,” said Thomas Zurbuchen, the head of NASA’s scientific mission, which built the telescope in collaboration with the European (ESA) and Canadian (ACS) space agencies, at a press briefing.

ESA Director General Josef Aschbacher congratulated himself on the fact that the Arianespace rocket, which “worked extremely well”, “put the spacecraft into orbit very accurately”. An important point, because proper injection into orbit saves fuel, James Webb would need to reach his final point and then operate.

Immediately after takeoff, the telescope flew over the Atlantic, then over Africa, until the final separation, which occurred at an altitude of 1,400 km and a speed of over 34,000 km / h. An on-board camera mounted on the upper floor of Ariadne showed this separation, and in particular the deployment of James Webb’s solar panels.

This critical operation will be followed by the second, the first of three course corrections, to reach its position at 1.5 million km approximately twelve hours after take-off.

The telescope will make it possible to better understand the formation of stars and galaxies and to observe exoplanets, of which astronomers are discovering more and more samples. 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.

Envisioned by NASA since the launch of Hubble in 1990, James Webb 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 observes space primarily in the region of visible light, James Webb ventures into wavelengths that escape the eye: the 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, the telescope’s scientific co-head for ESA. For example, the first galaxies, objects whose distance caused their light to turn red. Or young colonies of stars, hidden in the dusty clouds of their nurseries. Or the atmosphere of an exoplanet.

The necessary condition for the proper functioning of a telescope is an ambient temperature so low that it does not interfere with the examination of light.

The Hubble orbit is about 600 km above Earth. At this distance, James Webb would be unusable, heated by the Sun and its reflection on Earth and the Moon.

It will be placed 1.5 million km away at the end of a month’s voyage and protected from solar radiation by a heat shield of five flexible sails that dissipate heat by reducing the temperature (that is, 80 °) to -233 ° Telescope. will do it. Party.

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. . ,

For these maneuvers, NASA also implemented strict hygiene measures to avoid any contamination of the telescope’s mirrors, particulates or even charged breath…

It will take several weeks to find out if the telescope is ready for use. Its official entry into service is scheduled for June 2022.