IN PICTURES, IN PICTURES. Star, galaxy, nebula … Astrophysicists have been asked to decipher the images from the new James Webb telescope

Each image offers “for humanity a view of the universe we have never seen before”. These words from Bill Nelson, head of the American Space Agency (Nasa), sum up the value of the first images from the James Webb Space Telescope, which were unveiled on Tuesday, July 12, with great fanfare. This publication marks the beginning of the scientific operations of the most powerful space telescope ever designed, which astronomers around the world have been waiting for for years.

But what exactly do we see in these beautiful images of stars and galaxies? To help you understand them, franceinfo asked astrophysicists Anthony Boccaletti and Eric Lagadec to decipher them. “These are objects that have already been observed, but in a different way”explains the first. “These images just serve to show that this instrument has enormous potential, it is the beginning of a new era”thinks the other.

A cluster of galaxies

The first image from the James Webb Telescope, unveiled on July 11, 2022, shows a cluster of galaxies.  (NASA / AFP)

The first snapshot, unveiled by US President Joe Biden on Monday, shows a cluster of galaxies called SMACS 0723. “You have to imagine three different planes: The very clear stars that form crosses are in our galaxy. Then you see a supermassive cluster of white-colored galaxies, and the orange objects are distorted images of more distant galaxies.”exhibits Anthony Boccaletti, from the Paris Observatory.

By acting as a magnifying glass, the cluster of white galaxies makes it possible to detect very distant cosmic objects located behind it, an effect called gravitational lenses. “The redder these galaxies are, the farther away they are, and the more we see them in a time close to the Big Bang”, more than 13 billion years ago, adds Eric Lagadec. The astrophysicist from the Côte d’Azur Observatory uses an image to help us better understand these celestial bodies: “What we see represents a part of the sky that is so small that it can be hidden by a grain of sand held at arm’s length.”. On Twitter, he also compares it to an earlier image, taken from the old Hubble telescope, which makes it possible to realize James Webb’s precision.

Stephans Quintet

Stephans Quintet, in a picture taken by the James Webb Space Telescope and unveiled on July 12, 2022. (NASA / AFP)

Stephan’s Quintet is a compact group of galaxies, 290 million light-years away. white objects “are five interacting galaxies that interact and dance around each other”explains Eric Lagadec. “This helps highlight star-forming regionsadds Anthony Boccaletti. What you see with red is the gas and the dust that form stars. “.

The Carina trains

The Carina Nebula, in an image from the James Webb Telescope, unveiled on July 12, 2022. (NASA / AFP)

This image shows what a star-forming zone looks like from close by : a giant cloud of dust and gas. This Carina nebula is located about 7,600 light-years away. It is cut into two parts. Below an orange area where “We see gas, dust and stars forming“, describes Eric Lagadec. At the top a blue zone, “where we see stars already formed, which radiate and create places without gas”. “Not all the colors you see here are real, the telescope sees areas you can’t see with the naked eye, you have to interpret the light”continues Anthony Boccaletti, specifying that there is “a completely aesthetic work” bag.

A dying star

The Southern Nebula, in two images taken by the James Webb Telescope, unveiled on July 12, 2022. (NASA)

These two images, taken by two different instruments of the James Webb Telescope, show the southern nebula surrounding two stars, one of which is dying. “When a star dies, it emits gas and dust, that’s what we see in this picture”, decrypts Eric Lagadec. The structure of the fog, “in the form of a diabolo”betrays the presence of another, smaller star, which can be seen on the visualization to the right.

The spectrum of an exoplanet

The spectrum of the exoplanet WASP-96B, recorded by the James Webb Telescope.  (ESA)

This is the least spectacular image of this first delivery and with good reason: it is a spectrum, an analysis of the light emitted by an object to determine its chemical composition. In this case, the exoplanet – that is, a planet outside our solar system – is WASP-96 b. “By observing its main star, we are able to detect a small change in light as the planet passes in front of it, and this allows us to obtain information about its atmospheric composition.”, explains Anthony Boccaletti. The astrophysicist, however, wants to dampen the excitement that could arise around the mention of “water” (water) on this graph: this water is not in liquid, but gaseous form, which does not have the same potential in terms of life at all. development.

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