The five surprises of the James-Webb telescope

Stephan's Quintet, a group of five galaxies, seen by the James-Webb telescope.

The new star of astronomy. This is how we can nickname the James-Webb Space Telescope (JWST), a 10 billion dollar (9.3 billion euro) jewel that the American, European and Canadian space agencies took off on the day Christmas 2021. With its 6.5 meter diameter mirror, it is by far the largest telescope ever sent into space. Its observations began in the summer of 2022 and, now that the first annual cycle has ended, publications with spectacular images are rolling in uninterrupted, like waves on the beaches of a scientific ocean. The time has therefore come for a first essment.

Preliminary question: does this ultra-sophisticated machine work well? We remember, in fact, that in 1990, after the Hubble space telescope, predecessor of the JWST, had been put into orbit, researchers had discovered with dismay a sort of myopia, which had to be corrected in orbit in 1993 thanks to a mission of the American space shuttle Endeavor. An option excluded for the James-Webb which, positioned 1.5 million kilometers from Earth, cannot be repaired. Fortunately, no anomalies were reported during its commissioning.

Astrophysicists, on the contrary, have two reasons for satisfaction. The first holds “to the almost perfect launch carried out by Ariane-6”underlines Pierre-Olivier Lagageresearch director at the Atomic Energy and Alternative Energies Commission (CEA) and co-responsible for one of the four James-Webb instruments: “ Thanks to this, we were able to save on fuel and we have reserves for twenty-six years. » That is much more than the five to ten years initially hoped for. One more reason to take care of the machine and “pay close attention to the risk of breakdownadds Pierre-Olivier Lagage. Operations are carried out in such a way as to avoid as much as possible areas where micrometeorites could strike the mirror.”

The second reason to rejoice comes from the performance of the telescope, ures David Elbazalso an astrophysicist at the CEA: “The technical capabilities of the machine are completely there, with even slightly better characteristics than expected. » And on a scientific level, does the James-Webb, supposed to go back to the first sources of light in the cosmos, but also to attack the atmospheres of exoplanets, also live up to expectations? Positive response from David Elbaz: “Are we going further than what Hubble saw? Yes. Do we see planets orbiting other stars? Yes. Can we characterize their atmosphere? Yes. »

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