The James Webb Telescope has reached its final observation post 1.5 million km from Earth

Published on 24 Jan. 2022 at 22: 20

A new milestone for James Webb. The space telescope has finally reached its final orbit, 1.5 million km from Earth, NASA confirmed on Monday. It is since this point that he will soon be able to observe the first galaxies of the universe.

It activated its thrusters at approximately 20 hours (French time) in order to reach Lagrange point 2 or “L2”, ideal for observe the cosmos. “Welcome home, Webb!” exclaimed the boss of the American space agency, Bill Nelson, in a press release. “We have taken another step towards uncovering the mysteries of the universe. And I can’t wait to see the first new images of the universe from (the) Webb telescope this summer! “, he added.

A carefully chosen destination

At this carefully chosen orbit, the Earth, the Sun and the Moon will all be on the other side of its sun visor, which will ensure that it operates in the darkness and in the very great cold essential to the study. of the first cosmic rays via its infrared sensors.

This is the third time that the telescope has operated its thrusters in this way since its launch aboard an Ariane 5 rocket, on 25 December. The great impulse provided by the rocket had indeed been deliberately minimized to prevent the instrument from exceeding its objective, without any real hope of return, and it had to again, by small successive pushes, to place itself there.

A project for 10 billions of dollars

The James Webb telescope, whose cost for NASA is estimated at 10 billion dollars, is one of the most scientific equipment most expensive ever built, comparable to its predecessor Hubble or the huge CERN particle accelerator.

But while Hubble was placed in orbit around the Earth, Webb will orbit in the region of space called Lagrange point 2, where the gravitational forces of the Earth and the Sun are counterbalanced by the centrifugal force of the telescope, allowing a stable trajectory with less fuel usage. The new telescope will not be exactly at the L2 point but will oscillate around it in a “halo” at a distance similar to that of the Earth and the Moon, according to a six-month cycle.

James Webb’s positioning will also allow him to stay in constant contact with Earth via the Deep Space Network, a network of three large antennas in Australia, Spain and California.

A very dangerous operation

NASA had succeeded in early January in deploying – very perilous operation – the huge mirror of the telescope which will allow it to receive radiation emitted by the first stars and galaxies, formed more than 13, 4 billion years ago, less than 400 million years after the Big Bang.

James Webb, unlike Hubble, is equipped to perceive infrared signals, which will allow him to see not only older objects, but also the clouds of interstellar dust that absorb starlight and hide it from Hubble’s gaze. It must also take a big step in the exploration of exoplanets, orbiting stars other than the Sun. He will examine their atmosphere, looking for conditions conducive to the appearance of life.

Next step: its scientific instruments still need to cool down before being very precisely calibrated. Its first images should be transmitted in June or July.