“We must discover invisible galaxies”: why the images from the James Webb telescope are expected

Space enthusiasts around the world are holding their breath: the James Webb Space Telescope, the most powerful ever sent into orbit, is set to unveil its first color images of the universe on Tuesday, which promise to be spectacular.

Eliminating galaxies and stellar nebulae … NASA on Friday unveiled the names of the first five selected targets. But the images were jealously kept away from the eyes of the curious, to create excitement and surprise.

“The deepest picture ever taken of our universe”

I can not wait not to have to keep this secret anymore, it will be a great relief Said Klaus Pontoppidan, chief scientist at the Space Telescope Science Institute in Baltimore, responsible for James Webb’s operations.

By the end of June, NASA chief Bill Nelson had promised ” the deepest image ever taken of our universe The images must both impress the general public with their beauty, but also demonstrate to astronomers around the world the full power of on board scientific instruments. It is for this reason that they targeted a variety of cosmic objects.

Experts will thus be able to get an idea of ​​what James Webb is capable of, and practice interpreting the collected data using dedicated software. Gives the start of a great scientific adventure.

When I saw the pictures for the first time (…), I suddenly learned three new things about the universe that I did not know before “, Trusted Dan Coe, an astronomer at the Institute in Baltimore, and one of the lucky few in the trust. ” It completely blew me away. “James Webb Will” transform our understanding of the universe “, he testified.

majestic colors

The names of the observed cosmic objects are as poetic as they are enigmatic: the Carina Nebula and the Austral Ring – giant clouds of gas and dust where stars form -, Stephan’s Quintet – a compact group of galaxies -, or the galaxy cluster SMACS 0723, which acts as a magnifying glass that makes it possible to see the dim lights behind it, even further …

However, the likely majestic colors that will be revealed in the photographs will not be directly those observed by the telescope.

Light is refracted in different wavelengths, and James Webb works in infrared, which the human eye cannot perceive. Infrared light is also rich in colors, but is not in the visible spectrum, these will therefore be so translated in colors we can distinguish.

Thanks to these near- and mid-infrared observations, James Webb will be able to see through impenetrable clouds of dust for his predecessor, the mythical Hubble Space Telescope. Launched in 1990 and still in operation, it has a small infrared capacity but works mainly in visible light and ultraviolet.

Even when Hubble managed to take a picture of a distant galaxy, it could not distinguish a squirrel from an elephant. “, Summed up for David Elbaz, French astrophysicist.

James Webb, very different from Hubble

We will detect the formation of stars buried in interstellar dust, galaxies invisible because buried in dust crystallize “, He was enthusiastic, moved and impatient after discovering the pictures.

Other major differences between the two telescopes: James Webb’s main mirror is almost three times larger than Hubble’s, and it develops much further: 1.5 million kilometers from Earth, compared to 600 km for Hubble.

The first James Webb Telescope spectroscopy will also be released on Tuesday, a technique used to determine the chemical composition of a distant object. In this case WASP-96 b, a giant planet consisting mainly of gas and located outside our solar system.

Exoplanets (planets orbiting a star other than our sun) are one of James Webb’s most important areas of research. About 5,000 have been discovered since 1995, but they remain very mysterious.

The goal is to study their atmosphere to determine if they could prove to be habitable worlds and conducive to the evolution of life.

The publication of these first images will mark the official start of the very first cycle of scientific observation of the telescope.

Several hundred observation projects, proposed by researchers from around the world, have already been selected by a selection of specialists for this first year of operation.

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