Next-generation James Webb telescope to unravel mysteries of galaxy formation

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In three decades, the world’s largest and most advanced space telescope will scan the cosmos more deeply than its predecessors and, among other things, shed light on the mysteries of the formation of galaxies in the early Universe as well as the birth of stars in our own milk. Galaxy way.

the James Webb Space Telescope, named after former NASA administrator James Webb, will launch on December 22 from Europe Space port in French Guiana, aboard an Ariane 5 rocket. Looking back billions of years, it promises to fill in key gaps in our understanding of the history of our Universe.

“JWST will answer many questions from the edge of the universe. This will also allow us to study the atmospheres of planets in other solar systems in much more detail than possible otherwise, ”Mark McCaughrean of the European Space Agency and a member of the JWST science working group, told FRANCE 24.

Designed over thirty years ago and costing $ 9.7 billion, the telescope is the result of an international collaboration between the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Agency Canadian Space (CSA). Europe supplied 1.5 of the four scientific instruments in addition to the Ariane 5 launcher.

One of the most striking features of JWST is its primary mirror, which measures 6.5 meters in diameter and has 18 hexagonal segments. Once launched into orbit, these 18 moving segments will need to be aligned with extremely high precision (on the order of a nanometer) to form the main mirror.

Equipped with a giant sunscreen and four instruments including cameras and spectrographs, JWST will orbit the Sun at a distance of 1.5 million km from Earth and make observations primarily in infrared wavelengths.

“The first galaxies formed so far in time and so close to the Big Bang that by the time the light reaches us it is very faint and has been redshifted by the expansion of the Universe in the infrared. So you need a telescope that is powerful and works in the infrared – it also has to be cold to avoid shining in the infrared itself. JWST is all of those things, ”McCaughrean says.

Imaging of exoplanets

Other important objects that JWST will study are exoplanets – that is, planets orbiting stars far beyond our solar system. While previous missions have detected the presence of hundreds of these planets, JWST will go even further by directly imaging some of them and performing spectroscopy of the atmosphere around them.

One of the key instruments that will enable these measurements is called MIRI (for Mid-InfraRed Instrument) which was developed through a partnership between ESA, a consortium of European institutes, and NASA. MIRI consists of a camera, stellar coronographs and two spectrometers. Coronographs, developed by the LESIA laboratory at Paris Observatory, greatly reduce the flow of shiny objects compared to faint objects nearby. This will make it possible to observe exoplanets next to bright stars as well as active centers of galaxies.

In addition to revealing the mystery of the formation of the early Universe galaxies and the imagery of exoplanets, JWST will also examine our own Milky Way galaxy, improving our understanding of the birth of young stars and the formation of stars. planets around these stars.

According to McCaughrean, JWST will also be an important component of multi-wavelength astronomy in which instruments operating at different wavelengths are trained over the same part of the sky for a full analysis of a phenomenon.

“For example, the The Hubble Space Telescope has already performed extensive optical and ultraviolet observations of distant galaxies that JWST will track in the infrared, ”said McCaughrean.

JWST’s impressive features are the result of several innovative technologies. “The main mirror of the Hubble Space Telescope is 2.4 meters in diameter. JWST’s mirror is three times the size, but the entire observatory weighs only half that of Hubble. One of the main reasons JWST is so much lighter is that its mirrors are made of beryllium, not glass, ”he adds.

The other crucial element of the observatory is its giant sunshade which will only deploy once the observatory is launched into space. “The technology for this five-layer sun visor, the size of a tennis court, had to be invented because it didn’t exist before. ”

Made from a specially coated lightweight material called Kapton, the diamond-shaped lens hood will help cool the telescope to a staggering temperature of -223 ° C. “You will have about 300 kilowatts of sunlight coming in from one side of the sunshade while on the other side where the telescope will be placed, you will have a few tens of milliwatts,” says McCaughrean.

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