The universe through the eyes of James-Webb

Since its commissioning in July, the James-Webb Space Telescope (JWST), built by the US (Nasa), European (ESA) and Canadian (CSA) space agencies, has provided spectacular images of space with unprecedented precision and unprecedented data on the history of the stars. Placed in orbit 1.5 million kilometers from Earth, this technical jewel takes its pictures in the near infrared, thanks to its Nircam camera, which can detect stars or planetary systems in formation and in the mid-infrared, thanks to the Miri spectrocamera.

“The images revealed are breathtaking. JWST exceeds all expectations, it is a huge success, rejoices astrophysicist Sylvie Vauclair, professor emeritus at the University of Toulouse (1). They are of extraordinary resolution, with many details, that is the biggest surprise. We discover the intimate structure of known celestial bodies. JWST brings a wealth of information that will provide years of work for professional astronomers to better understand the universe. »

A kindergarten of stars

On July 11 and 12, the ball opened with a lavish fireworks display: a stellar nursery in the Carina Nebula, 7,600 light-years from Earth, Stephan’s Quintet, that group of interacting galaxies, two of which are merging, and finally the Southern Ring, a expanding planetary nebula, 2,000 light years from our planet.

In these first recordings, we can see very distant galaxies and, above all, the well-known phenomenon of gravitational arcs, called “Einstein’s arcs”. ” These luminous figures are distorted views, in the form of circles, of other galaxies far beyond those clearly visible in the image, explains Sylvie Vauclair. The rays that reach us from these hyper-distant objects are deflected by the material they encounter in their path, hence the distortion that appears in the image. »

On July 21, the general public was able to admire the Glass-z13 galaxy, the most distant and oldest known (it is 13.5 billion years old). In the image, given the timing of its light reaching us, it is revealed in the state it was in 300 million years – first – after the big bang…

On July 22, NASA released a snapshot of the spiral galaxy Messier 74, nicknamed the Phantom Galaxy, 32 million light-years away. “It is to me the most amazing picture, says Sylvie Vauclair. It appears as a kind of canvas everywhere perforated with circular shapes. Be careful, make no mistake about it; in fact, they are not holes, but large dense clouds, which appear dark in the galaxy precisely because of their density. »

See what was invisible

On August 2, NASA released the incredible images this time of the Cartwheel galaxy, 500 million light years away. “It is impressive, surrounded by a brilliant ring of very young stars, formed during collisions with other galaxies that are still visible nearby”, explains Sylvie Vauclair. A few days later we discover a new aspect of Jupiter, the gas giant on whose surface winds and storms swirl. Thanks to one of its spectrographs, the telescope has also made it possible to characterize the atmosphere of the exoplanet Wasp-96b, another gas giant located 700 light years away, and to detect carbon dioxide there… Or even get a direct mid-infrared image of the exoplanet HIP 65426b, about 14 million years old.

In early September, JWST’s Nircam camera is still working wonders: We detect the formation of thousands of stars in the Tarantula Nebula, located 161,000 light-years away. Ditto in the constellation Orion, located only 1,270 light years from Earth. The latest shot describes Neptune, the most distant giant and icy planet in the Solar System, and seven of its fourteen satellites, including Triton, clearly visible for the first time.

JWST’s first challenge has been met: to see what was invisible until now, to bring new scientific knowledge about the history and evolution of galaxies and stars. These images have since been the subject of analysis and interpretation, also among amateurs or independent astronomers. Already almost 150 scientific publications have used the first data from JWST: they cover large fields of astronomy, from the interstellar medium of our galaxy to cosmology, with in particular the detection of several galaxies that are probably the most distant and the youngest. known to date”, emphasizes Pierre-Alain Duc, director of the Strasbourg Astronomical Observatory.

Normally, these observations are reserved for researchers for a year. But the JWST consortium has chosen to make some of the data available to everyone and immediately. Something to fascinate a wide audience, who are not done wondering. The James-Webb Telescope is to continue its excellent harvest for twenty years…


Find all the interviews with Sylvie Vauclair and Pierre-Alain Duc on

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