On the 25th of December 2021, the Webb telescope, the largest and most complex space telescope ever built, was launched from Kourou by an Ariane 5 rocket. Two weeks later the telescope was fully deployed and end of January, it was in orbit around the Lagrange point L2 (1.5 million km from the Earth). Then the 18 hexagones which constitute the primary mirror were phased and the four instruments commissioned. In many regards, the performances are better than the requirements and at the best we could expect. In July, science observations have started. Thanks to its large collecting area (25 square meters) and large wavelength coverage (0.6 – 28 microns), this flagship NASA mission with participation of Europe and Canada, will impact many fields in Astrophysics. Indeed , it allows to observe further away than Hubble and to probe the Universe at the epoch when the first galaxies were formed, a few 100 millions years after the big band. It also to probe the regions where stars form with an unprecedented acuity. Another example of fields which will benefits from Webb observations, is the study of exoplanets. In the seminar, I will present the performances and the first results from Webb, focusing on exoplanets.
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