how the James Webb telescope revolutionized astronomy

This is the space telescope of all superlatives, launched on December 25, 2021, more than 1.5 million kilometers from Earth and of which we can admire, since this summer, spectacular shots. James Webb, built by the American, European and Canadian space agencies, was developed in order to continue the work of its predecessor Hubble. OThe most powerful space observatory ever built, it is tasked with observing the farthest reaches of the Universe, understanding the formation of the first stars, planets and galaxies created after the Big Bang, and determining if there are extraterrestrial life forms. A real window on a world hitherto unreachable.

The documentary James Webb, Journey to the Origins of the Universe, directed by Martin Gorst and broadcast Thursday October 13 at 9 p.m. on France 5, relates in an educational and detailed way the design and manufacture of this telescope which cost nearly 10 billion euros and mobilized 10 000 scientists and engineers for almost 30 year.

The tool James Webb’s flagship is his huge primary mirror. Its development was a challenge for the engineers of the Institute of Space Telescope Sciences, because it had to be able to fit into the fairing of a rocket. The idea was therefore to create a segmented reflector with a diameter of 6.5 meters. It is composed of 18 hexagonal mirrors, individually adjustable and which can bend like an origami.

“With James Webb, we wanted to go even closer to the birth of the Universe, so to see, of course, even fainter objects, hence the need for a larger collector“, explains Pierre Bely, a French engineer at the European Space Agency, who participated, from the start, in the design of James Webb and his mirror.he study of the reflectors of the largest telescopes in the world manufactured in the 1990s, located at the WM Keck observatory on the island of Hawaii, has enabled scientists to design this jewel of even more powerful technology.

“We knew that we could make a mirror as a kit and that the Keck observatory had already done it with its telescope. The idea is always easy to find, it is the details of the implementation that are complicated“says in the documentary the American John Mather, astrophysicist and cosmologist at NASA, Nobel Prize in Physics in 2006.

This implementation required the manufacture of eight machines dedicated to polishing the eighteen small hexagonal mirrors. Two and a half years were necessary for these segments to be completely smooth. Because if the surface of the reflector is not perfect, the images returned by the telescope will be blurred. “The difficulty comes from the fact that the primary mirror consists of 18 segments, and the surface must be as aligned as possible”, assures Jay Daniel, the American research director who supervised its construction.