"Extraordinary detail": what images from the James Webb telescope reveal

In scientific memory, rarely has such a media drumbeat made so much noise for their work.

"Extraordinary detail": what images from the James Webb telescope reveal

In scientific memory, rarely has such a media drumbeat made so much noise for their work. Do you realize on the night of July 11 to 12, Joe Biden, himself, live from the White House, wanted to comment on the first image from the James Webb Space Telescope (JWST) to qualify it as "historic". It looks like the very beginning of the space conquest when President Kennedy launched the Apollo missions towards the Moon.

The image revealed this night is however not the most artistic that the JWST can achieve. It has just been called "the deepest ever taken from our universe" in the words of Bill Nelson, the head of the American space agency (Nasa). “Personally, I find it particularly beautiful,” enthuses David Elbaz, Scientific Director of the CEA's Astrophysics Department in Saclay. Not for what it allows us to see, we poor mortals, since the main characteristic of the JWST is to operate in the infrared (a wavelength invisible to human eyes), but for what it describes with unequaled resolution for experienced astrophysicists.

"It is a cluster of a thousand galaxies called SMAC 0723, particularly interesting for its large central galaxy and its faintly luminous halo which could correspond to the light of stars having been ejected into intergalactic space. But this photo is especially precious to us for what it allows us to glimpse further", continues David Elbaz. Indeed, the famous cluster is located 4.6 billion light-years away but it works like a magnifying glass - we are talking about an effect called gravitational lensing - making it possible to reveal, behind it, much more distant cosmic objects since located more than 13 billion light-years away. "In the end, we don't know much about what happened between 13.8 billion (Big Bang) and 13.3 billion light-years away and that is indeed the main mission of the James Webb of us shed light on the beginnings of the universe", adds David Elbaz. On the photograph of the deep field of the universe, the distant galaxies appear in the form of fine luminous arcs just as we also see light coming from stars torn from their galaxy. “It will take several months to scrutinize this image in detail, but the first results could come in September,” hopes the CEA astrophysicist.

Everything is going very quickly in the end, since the space telescope with a giant mirror 6.5 meters in diameter, launched in December 2021 by an Ariane 5 rocket and stationed at the Lagrange L2 point located 1.5 million kilometers from Earth, is now qualified as "fit for work". After six months of meticulous deployment and a battery of tests, each of the four on-board instruments is fully satisfactory.

The scientific work therefore began in June and the first image disclosed in the presence of Joe Biden is part of this first harvest. This Tuesday afternoon, four other photos were revealed by NASA. "Some of them are astoundingly beautiful, but above all they highlight all the capabilities of the JWST", describes Pierre-Olivier Lagage of the CEA, scientific manager of the MIRI instrument (Mid InfraRed Instrument), the only one able to operate in the mid infrared. One of the most amazing comes from Stephan's Quintet, a cluster of galaxies in the constellation Pegasus - "one of the most chaotic places in the universe", according to Elbaz. But the most beautiful comes from the Carina Nebula, 7,600 light-years from Earth, considered the largest star nursery in our galaxy. “Given the quality, we will be able to zoom in and reveal extraordinary detail,” enthuses David Elbaz. The other nebula presented today by NASA is that of the southern ring (2000 light-years): "It loses its envelope of expanding gas, explains the researcher. It is crossed by grains of dust and molecules and we hope to finally know its composition."

The Southern Ring Nebula captured by the James Webb Telescope.

Handout / NASA / AFP

This chemical work, the JWST will also do with exoplanets - those planets that orbit around a star other than our Sun. Nearly 5,000 have been discovered since the first in 1995. "We have moved from the era of detection to that of characterization," assures David Elbaz. One of the photos shown today is of exoplanet WASP-96b, a gas giant. "Here again, what needs to be shown are the telescope's ability to find biosignatures (methane, oxygen, ammonia, etc.) to analyze the chemical composition of the atmospheres", explains Pierre-Olivier Lagage. Finding traces of water there would therefore be great news.

But for the exoplanet specialist at the CEA, beyond today's demonstration, the objective to be targeted for the JWST is called Trappist-1B, an Earth-sized rock located 40 light years away. which concentrates many hopes for the specialists hoping, finally, to discover there irrefutable proofs of habitability. The scientific work of the James Webb Telescope has only just begun and promises many revolutions in the knowledge of the history of our universe.

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