Monday, January 24

Two weeks after take off, the fully deployed James Webb telescope

The James Webb Space Telescope successfully completed the last stage of its deployment on Saturday, along with that of its main mirror, and is now in its final configuration to be able to begin, in just over five months, its exploration of the cosmos.

The telescope’s iconic main mirror measures around 6.5 meters in diameter, so it was too large to fit into a rocket as it was when it lifted off two weeks ago. Its two sides must therefore have been folded back.

The first of these two wings was deployed on Friday, and the second opened on Saturday morning, as planned, NASA said. The space agency teams continued to lock it in place, however, in order to secure it permanently.

“I am moved,” said Thomas Zurbuchen, head of scientific missions at NASA, live by video. “What an extraordinary step.”

Deploying such a telescope in space, not only of its mirrors but also of its heat shield earlier this week, was an ultra-perilous procedure that had never been attempted in the past.

Astronomers around the world can breathe a big sigh of relief today, as the mission now looks very successful.

Before being operational, however, the telescope will still have to reach its final orbit 1.5 million kilometers from Earth (it is already more than a million kilometers from us).

Each hexagonal segment forming this immense primary mirror, covered with gold in order to better reflect the light, will also have to be carefully adjusted. Scientific instruments will have to continue to cool, and be very precisely calibrated.

Worth some $ 10 billion, James Webb is flown from Baltimore on the US East Coast. NASA broadcast live footage from the control room on Saturday morning, where dozens of engineers applauded with joy at the announcement of the full deployment.

– Ends of the Universe –

The most powerful space observatory ever designed, James Webb must notably make it possible to observe the first galaxies, formed only about 200 million years after the Big Bang.

It also needs to take a big step forward in exploring exoplanets, which orbit stars other than the Sun. He will examine their atmosphere, in search of conditions conducive to the appearance of life.

Also planned are closer observations, in our solar system, of Mars or Europe, a moon of Jupiter.

To detect the faint gleams from the far reaches of the Universe, James Webb needed a main mirror larger than any sent into orbit so far.

The secondary mirror, much smaller and placed at the end of a tripod in front of the main mirror, had been successfully deployed on Wednesday. It is used to focus the light from the primary mirror, before directing it to a third mirror and the four scientific instruments.

On Monday, the mission had reached a major milestone with the most difficult deployment, that of the heat shield.

Made up of five layers each the size of a tennis court, but as thin as a hair, this lens hood protects scientific instruments from the heat of our star.

These layers were carefully unfolded and stretched one by one. The face closest to the Sun can reach 125 ° C, and the furthest away -235 ° C.

The great novelty of this telescope is that it will operate only in the near and mid infrared (wavelengths invisible to the naked eye), and its instruments can therefore only operate in total darkness and at temperatures extremely low.

James Webb must operate for at least 5 years, and potentially up to 10 years.

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