James Webb: the adventure begins!


This lavish cosmic rock, 16 light-years (ly) wide, is a very small part of the Carina Nebula, a giant cloud of gas and dust within which stars are born in abundance. Some of them twinkle in the image: their radiation is so powerful that it dug this gaping cavity in the nebula, the details of which are visible in infrared thanks to the telescope’s formidable resolving power. In fact, since the James-Webb Space Telescope (JWST) captures light frequencies invisible to the human eye, its images are systematically colorized before publication. “Infrared is the strength of JWST compared to the Hubble telescope, explains Pierre-Olivier Lagage, astrophysicist at CEA and joint scientific director of the telescope’s MIRI imager and spectrograph.

This is what makes it possible to penetrate the clouds of gas and dust and to observe this nebula in transparency. ” This is how astronomers think they can unlock the secret of the birth of stars…and even the planets that orbit them!




The first deep field in the universe photographed by JWST is breathtakingly beautiful. In the foreground are stars in our galaxy, recognizable by their six characteristic aigrettes: they are produced by the diffraction of light at the edges of the telescope’s hexagonal mirror. The second layer consists of these whitish galaxies, which are much more distant: they are part of the galaxy cluster SMACS J0723, located 4.24 billion light years away. The gigantic mass of the cluster bends space-time and produces a gravitational lensing effect that distorts and amplifies the image of background galaxies even further away! They are visible in orange. Their light reaches us from the depths of space and time some 13 billion years ago, just a few hundred million years after the big bang. “Twelve and a half hours of observation was enough to generate this image, that’s very little, notes Pierre-Olivier Lagage. No doubt it contains the most distant galaxies ever observed!” And this is only a very small part of the sky: the field of view is the size of a grain of sand held at arm’s length… or 1/25 millionth of the entire firmament.




It happened in our galaxy only a few thousand years ago… A sun at the end of its life began to swell into a red giant, then expel its hydrogen envelope into space as its heart contracted to a tiny white dwarf. The Southern Ring Nebula he left behind is a sublime sight, especially under JWST’s gaze. The molecular hydrogen mantle in orange is seen here with details of formidable finesse! The blue halo comes from the hydrogen plasma electrified by the white dwarf, which continues to shine in the heart of the image, drowned in the light of its companion star. This white dwarf actually orbits another star; it was this interaction that sculpted the various layers of the gas envelope as it disappeared into space. The companion star itself is nearing the end of its life: in a few thousand years it will experience the same fate and produce its own nebula. By observing these gas clouds, James-Webb will make it possible to study in detail the future death of our own sun. Because in 6 billion years our star will also give way to a white dwarf and its nebula before disappearing forever.



At 290 million ly, four galaxies spin around each other, tearing gas and millions of stars – the long white streaks. Only four? Although we can distinguish five galaxies – the halo at the bottom is actually one – Stephan’s Quintet is actually a quartet: the galaxy on the left is in the same line of sight, but it is seven times closer to us than the other four (40 million al). JWST’s astonishing resolution also makes it possible to distinguish some of its stars individually – the countless blue and red dots. As for the upper galaxy, it is home to a supermassive black hole 24 million times the mass of the Sun and 40 million times brighter.

The spectroscopic analysis of its light revealed the presence, at the edge of the black hole, of neon, argon, sulfur, iron… So many elements forged in the heart of the stars that the black hole consumes. It spits out matter in the form of two relativistic jets, which are not visible here, but which the telescope was nevertheless able to analyze.

“It is fascinating to be able to extract so much information from the first images, says Pierre Ferruit, science co-leader of the James-Webb mission for the European Space Agency (ESA). From the ground it is very difficult; this shows the full power of this telescope. “



It was July 11 from the White House. US President Joe Biden announced the successful commissioning of the James-Webb Space Telescope, the new flagship of NASA’s space fleet. And revealed the first pictures. After its launch on an Ariane 5 rocket on December 25, it took another six months of preparation. “Whether it was the insertion of the heat shield, the phasing in of the mirrors or the ignition of the instruments last June, everything went admirably well, says Pierre-Olivier Lagage, astrophysicist at the Atomic Energy Commission (CEA) and scientific co-principal of the telescope’s MIRI imager and spectrograph. It was an intense time, but so exciting! A period of my life that I will never forget. When the first data arrived, when we understood that everything had worked for the best, it was extraordinary.

It was an intense period. When the first data arrived, it was extraordinary! PIERRE-OLIVIER LAGGING Astrophysicist at CEA, scientific co-leader of MIRI

James Webb captures the Orion Nebula


As soon as it was switched on, the telescope was already producing the best images of the sky ever taken in infrared. “We didn’t expect anything so amazing, acknowledges Mathilde Jauzac, a specialist in distant galaxies at the University of Durham, in the UK. So much so that our team and I literally jumped on the data to publish a first scientific paper that we wrote in just three days! The article in question consisted of characterizing the mass distribution of the SMACS J0723-73 cluster. “The data was expected to be better than Hubble, but not to this extent, adds his colleague Guillaume Malher. JWST is even more amazing than we thought. “ An enthusiasm shared by Pierre Ferruit, the scientific director of the telescope at the European Space Agency (ESA). “In my opinion, the real strength of the telescope lies not so much in its images as in the exceptional quality of its spectra.”, he believes. In fact, the telescope was also designed to analyze the different frequencies of light emitted by celestial bodies and to derive information about their chemical composition.

To demonstrate this, NASA has published the transit spectrum of the gas giant exoplanet WASP-96b in the constellation Phoenix. We clearly distinguish the signature of the water clouds: thanks to JWST, we now know that the weather is mixed on a planet 1,150 ly from Earth. “The telescope is so stable that we were able to clearly observe this planet passing in front of its star without any special data processing, enthused Pierre-Olivier Lagage. This is extremely promising for future spectra. “ Among them, the long-awaited from the star Trappist-1, around which orbit three Earth-like planets in the habitable zone. More than 200 hours of observation of this system are planned in the first year alone. Enough to examine their atmosphere… if they have one.

And that’s just the beginning: the telescope has enough fuel to last its mission for twenty years. All the while, he will relentlessly jump from target to target and revolutionize all areas of astrophysics. Already, it has provided other images of nebulae, made it possible to identify the most distant galaxies ever observed, or even to probe the atmospheres of exoplanets. With each of its publications, scientists from around the world flock to the data to unravel the incredible mysteries of the cosmos. The James-Webb Space Telescope revolution has only just begun.

James Webb: Telescope Reveals Spectacular New Photos!

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