nebulae, group of galaxies, “deep field”, exoplanet … The first objects scrutinized by the JWST illustrate the diversity offered by astronomy in infrared. Over the course of their unveiling, we can compare them with the results of its predecessors, Hubble and Spitzer.
by
The American (NASA), European (ESA) and Canadian (ASC) space agencies will unveil on Tuesday July 12 the first images taken by the largest of space telescopes, the James-Webb (JWST), launched in December 2021 by An Ariane 5 rocket. They concern five different regions of the sky and have been chosen to illustrate the unprecedented performance of the instrument, in comparison with its predecessors, Hubble and Spitzer. Before the curtain rising, here is a presentation of these objects, and a sample of the way they were known to us before the advent of the James-Webb
Deep field, Smacs 0723
For this first image, the suspense is finished. The American president, Joe Biden, broke the embargo agreed with European and Canadian space agencies to present it in preview, Monday, July 11, from the White House, before a tour of the Middle East. We see an impressive cloud of multicolored light spots on a black background. They are hundreds, even thousands of galaxies, concentrated in a very small portion of the sky, equivalent to the size of a grain of sand at the end of an arm.
of one of these galaxies, white on the right, we can clearly see our arms in spirals, almost indistinguishable for Hubble, who had taken the same cliché. The image also strikes with very white points with eight “branches”. These are stars of our galaxy in the field of vision of the telescope. The “branches” betray the particular geometry of its mirror made up of 18 hexagons: the light diffracts on the tiny borders between them and creates these particular figures.
Other points are also remarkable, mainly massed in the center, under the most brilliant star. It is a compact heap of galaxies, Smacs 0723, more than 4 billion light years from the earth, and which explains the presence of orange arcs in the photo. Its enormous mass deforms space-time and curves the light rays in its vicinity, in particular those from the background. So much so that JWST sees several images of the same galaxy behind the cluster. If it was exactly aligned behind, you would see a perfectly circular ring. The interest is that this amplifies this distant light and therefore allows you to see even more distant objects. “It’s like a second telescope”, explains Johan Richard, astronomer at the astrophysical research center of the Lyon Observatory.
This is where JWST reveals that he is a time machine: he sees objects whose light has taken more than 13 billion years to us Coming, while Big Bang took place 13.8 billion years ago. Astronomers will therefore be able to see and study the very first stars and galaxies of the universe, and push the limits reached by Hubble.
You have 38.09% of this article to read. The continuation is reserved for subscribers.