“James Webb Space Telescope images are extraordinary”

Astrophysicist at CNRS and responsible for one of the observation programs on this telescope, Olivier Berné comments on the very first images of the James Webb Space Telescope (JWST), published today by the American (NASA), European (ESA) and Canadian (CSA) space agencies.

With this image of the Carina Nebula, a nursery of stars four times larger and more luminous than the Orion Nebula, the JWST promises great discoveries to Olivier Berné’s team. Copyright NASA, ESA, CSA, and STScI

You have finally seen the first images of the James Webb Space Telescope (JWST) launched last December. What do you think of them?
Olivier Berné (1). It is very moving! These images are extraordinary, with a depth and detail never before obtained with previous ground-based and space-based observatories, such as Hubble. The first results show a remarkable sensitivity, of the order of 6 to 10 times greater than before. This allows either to observe, finally, very distant objects like primordial galaxies, or to better see objects closer to us but very faint, like stars or planets in formation. On the other hand, there is much more information in these images which have a high resolution thanks to the 6.5 meter diameter mirror of the James Webb. Concretely, in terms of details, it is a bit like going from an impressionist painting to a realistic style.

The SMACS 0723 galaxy cluster is so massive that it distorts and amplifies the light of objects behind it. In addition to the capabilities of the JWST, this makes it possible to observe extremely distant galaxies with very low luminosity, thus offering “the deepest image ever taken of our Universe,” says Olivier Berné. Copyright NASA, ESA, CSA, and STScI

The JWST observes in the visible spectrum but mainly in the infrared. Why is this?
O. B. The infrared corresponds to wavelengths longer than those that make up the visible spectrum. Observing in the infrared allows us to go further back into the past of the Universe and to look at galaxies that formed in the early ages of the Universe.

Indeed, as the Universe is expanding, the light signal of these early galaxies is strongly red-shifted and leaves the visible spectrum. It is therefore necessary to look for their light in the infrared to understand the nature of the first stars that existed in the Universe and how they were formed just after the Big Bang, about 13.5 billion years ago.

The deep field of distant galaxies seen in this image perfectly illustrates this capability of JWST. These wavelengths also allow us to observe, for example, newborn stars or planets through the cocoons of dust and gas that surround them.

Located in the Vela constellation at about 2000 light-years from the Earth, the Southern Ring Nebula is a planetary nebula. It is an expanding cloud of gas and dust, expelled by a star at the end of its life, which gave the white dwarf visible in the center. “The quality of the details is astonishing: we can see a whole granular texture that was previously invisible,” Olivier Berné enthuses. Copyright NASA, ESA, CSA, and STScI

Do scientists use these images for their research?
O. B. These images use false colors to make them aesthetically pleasing while showing information that is not normally visible to the naked eye. Scientists do not directly use these color images to work. They are mainly interested in the data collected by each filter of the telescope, at specific wavelengths for the images or via data from spectrographs. This gives information about the temperatures, densities and chemical compositions of the observed objects, and sometimes their movements. We can thus understand the physical phenomena at play.

The JWST reveals the chemical composition of the atmosphere of the exoplanet WASP-96b, a gas giant half the mass of Jupiter, orbiting its star, located 1120 light-years from Earth (in the Phoenix constellation), in less than 4 days. The spectrum reveals water in different states at several depths in the atmosphere, “which proves the impressive capabilities of the instruments! Copyright NASA, ESA, CSA, and STScI

But the James Webb does not only have a scientific mission. With its fantastic images that move and touch the general public, the Hubble telescope has had a strong influence on the way humanity represents the cosmos, on the collective imagination of the Universe in which we live. This is a fundamental role, at least as important as the scientific discoveries, which the JWST will certainly continue. I had bet with my colleagues that there would be a wink to Hubble’s work in the images broadcast today and the one of the Carina nebula proves me right!

But space agencies are also releasing data today that will be valuable to you. Can you explain how?
O. B. Today, the agencies are broadcasting these wonderful images, but also all the observations that were made and the data that were produced during the test phase. These data have an important scientific interest. Indeed, they will allow us to evaluate the quality of the different instruments and to test the data processing algorithms that we have prepared. We, astronomers and astrophysicists, are looking forward to finally doing some science with this telescope that we have been waiting for several decades!

Your own observations will take place between September 10 and October 3. What are you looking to analyze and how is JWST an asset to your project?
O. B. Our team is coordinated by three leaders: Els Peeters at the University of Western Ontario in Canada, Émilie Habart at the Institute for Space Astrophysics (2) and myself. This trio coordinates an international team of about 150 people in 18 countries, with a tight team of about 30 researchers. We have obtained 40 hours of observation time to study the Orion Nebula, a cloud of gas and dust at the heart of the constellation of the same name. Places are hard to come by: for this first wave of projects, only thirteen have been selected worldwide, that is to say about one lucky person for every ten candidates, and we are the only program with a main responsibility for France.

This group of galaxies, the Stephan quintet, located 290 million light-years away, is the first compact group of four interacting galaxies, and one galaxy in another plane, discovered in 1877. “We have the impression of being able to zoom to infinity and find more and more details, it’s extraordinary!”, comments Olivier Berné. Copyright NASA, ESA, CSA, and STScI

The Orion Nebula is interesting for two reasons. First, it is a region of star and planet formation at least partially representative of the environment in which the Solar System was formed. Studying it will allow us to go back in time to better understand, by analogy, the formation of the Sun and the planets that surround it, like the Earth.

On the other hand, the distant galaxies observed by the James Webb are at a period of their evolution during which they form many stars. Their infrared radiation is therefore dominated by a light signal similar to that received from the Orion nebula. The difference is that Orion is close enough to observe different regions of the nebula with different physical parameters (gas temperature and density, star formation rate and radiation field intensity, etc.). Our project is therefore to provide models linking the shape of the received light signal to these parameters, a kind of standard that will allow to interpret the signals received from distant galaxies. We have been preparing this project for almost ten years, and the observations made will be at the heart of our research for several years!

A giant in the service of knowledge

The JWST is the largest and most powerful space telescope ever launched. It is designed to better understand our Solar System, observe distant worlds around other stars, and probe the origins of the Universe. It is the result of an international partnership between NASA, ESA and CSA. ESA provided two of the four scientific instruments of the James Webb: the NIRSpec spectrograph and 50% of the Miri spectrograph and imager. Several laboratories attached to the CNRS participated, such as the Laboratoire d’études spatiales et d’instrumentation en astrophysique (3), the Laboratoire d’astrophysique de Marseille (4) or the Institut d’astrophysique spatiale (5). The telescope was launched on December 25, 2021 on an Ariane 5 rocket from the European Space Center in French Guiana. With its 6.5-meter mirror span, it is now orbiting the L2 Lagrange point of the Sun-Earth system, located 1.5 million kilometers from Earth on the side opposite the Sun.

IRAP Contact

  • Olivier Berné, olivier.berne@mickael-coriat

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