What do the first images taken by the James Webb telescope reveal?

” Breathtaking ! Unbelievable ! exclaimed scientists and the general public upon discovering the first images sketched by the James Webb telescope. These shots, taken over the past few weeks, and to say the least spectacular, indeed, reveal details never before glimpsed. Six months after its launch, the most powerful space telescope in the world is working wonderfully, even “beyond expectations”, as evidenced by these prodigious tests obtained during its operational period.

A first image was unveiled in preview Monday evening at the White House, in the presence of the American president, Joe Biden. This is the “deep Webb field” image, the deepest and sharpest image ever obtained of the distant Universe in infrared radiation. In this image appears the galaxy cluster SMACS 0723 as it was 4.6 billion years ago, and in which is gathered a multitude of galaxies of different colors, each with different characteristics.

The combined mass of all the galaxies in this cluster also plays the role of gravitational lens which has made it possible to magnify and highlight much more distant galaxies, which had formed less than a billion years ago. the Big Bang, which is believed to have taken place around 13.5 billion years ago.

See the invisible

“By working in the infrared, the James Webb telescope makes it possible to see further into the Universe than the Hubble telescope. By a phenomenon similar to that of the Doppler effect (which causes the frequency of the sound emitted by a train, for example, to change depending on whether it is approaching or moving away), the wavelength of the light what comes to us from distant galaxies — which are moving away from us more and more rapidly due to the expansion of the Universe — is stretched and thus finds itself in the infrared. For Hubble, which looks mainly in the visible, these objects therefore became invisible. With Webb, we can therefore go back further in time. We should be able to go back a few hundred million years after the Big Bang,” explains Erick Dupuis, director of space exploration development at the Canadian Space Agency.

The second shot that was revealed to us on Tuesday is rather that of the spectrum of the atmosphere of the exoplanet WASP-96 b located 1150 light years from us and which revolves around a star similar to the Sun.

To do this, the Canadian instrument NIRISS (Near Infrared Slitless Imager and Spectrograph) captured the spectrum of light from the star that passed through the small ring of atmosphere surrounding the exoplanet as the latter passed in front of its star. The spectrum thus obtained contains the spectral signature of all the molecules present in the atmosphere of the planet.

However, the analysis of the spectrum of WASP-96 b confirmed “unambiguously the presence of water molecules in the atmosphere” of this gaseous giant of a size slightly larger than Jupiter and having a mass approaching that of Saturn.

“This spectrum, which is the most detailed ever obtained from an exoplanet, demonstrates Webb’s ability not only to detect exoplanets, but to determine the chemical composition of their atmosphere”, enthusiastically underlines René Doyon, principal investigator of the Canadian instruments. NIRISS and FGS (Precision Guidance Detector).

Southern Ring Nebula

The third image shows two shots of the Austral Ring Nebula, one taken in the near infrared, on the left, and the other, in the mid-infrared, on the right. Located 2500 light-years from us, this nebula is the scene of the last stages of the life of a star, which appears as a small red dot in the center of the image on the right.

“The mid-infrared (on the right) allowed us to distinguish two stars in the heart of the nebula: a redder star which has just died and which, in dying, created this so-called planetary nebula. Right next to it, another star, white for its part, is still alive, and is also visible and bright in the center of the left image. However, the red star is almost invisible in the image on the left because it is surrounded by dust. We needed to go even further into the mid-infrared to see it behind the cosmic dust that envelops it”, explains Nathalie Ouellette, in charge of scientific communications on Webb in Canada, and coordinator of the Institute for Research on exoplanets from the University of Montreal.

Stephan Quintet

For its part, the fourth image notably depicts the violent gravitational interactions that take place between four galaxies of Stephan’s Quintet, which includes five galaxies, two of which are about to merge in the cloud on the right. “The Webb telescope allows us to see how collisions between galaxies induce the birth of new stars in each of them”, underlines Ouellette while specifying that it is the shock waves of these cataclysms which condense the gases of the galaxies into new stars.

Webb also hinted at the presence of a supermassive black hole in the highest galaxy in the image. “If we zoom in on this galaxy, we can see energetic jets coming out of the black hole and which tell us that it is very active”, indicates the astrophysicist. Thanks to the unprecedented level of detail provided by Webb, it will be possible for scientists to determine the rate at which black holes are growing.

star nursery

In the last breathtaking cosmic landscape presented to us, this time we discover a star nursery named NGC 33245 which is located in the Carina Nebula. “The power of the Webb telescope allows us here to see the very beginning of the birth of some of the stars. Birth is a stage in the life of a star that lasts a very short time, only a few million years, and technically it is difficult to observe such a stage because the star is then completely surrounded by dust. But thanks to infrared light, Webb pierces this dust, which allows us to see the birth of stars which, until now, was impossible to observe, ”explains Mme Ouellette.

“All these images were obtained after only 120 hours of observation during a specific demonstration program. This is only the very beginning of what Webb will reveal to us…” emphasizes René Doyon.

The space telescope mission is now entering its operational and scientific phase.

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