What the James Webb telescope is teaching us

Since the James Webb Space Telescope began full operations in 2022, it has consistently surpassed even the most optimistic expectations of the scientists who built it. Capable of observing the universe in infrared light, the telescope can detect objects so distant and so faint that they were invisible to its predecessor, Hubble. Some of the early results have already forced astronomers to rewrite parts of their textbooks. Webb has spotted galaxies that appear to have formed surprisingly soon after the Big Bang. According to standard models, galaxies of that size and brightness should not have existed so early. Either the models need to be adjusted, or our understanding of how galaxies grow needs a more dramatic revision. Closer to home, Webb has analysed the atmospheres of planets orbiting other stars. By studying how light passes through these atmospheres, scientists can identify the chemical fingerprints of different molecules. Water vapour, carbon dioxide and methane have all been detected. None of these results prove the existence of life, but they bring the question within range of serious investigation for the first time. Of course, no instrument is perfect. The telescope cost roughly ten billion dollars and was delayed by years. Some critics argue that the same money could have funded hundreds of smaller missions. Yet for all the controversy, almost everyone in the field agrees that Webb has already paid back its investment in pure scientific value. The truly remarkable discoveries, most experts suggest, are still ahead.