The telescope Galileo Galilei first pointed at the heavens in 1609 had a lens no wider than a slice of cucumber. Yet with that modest tool, he saw the rings of Saturn, the moons of Jupiter—and sparked a scientific revolution that toppled Earth as the center of the cosmos. Astronomy has come a long way since then. But when the James Webb Space Telescope launches in December, with a 6.5-meter mirror that would tower over Galileo himself, it will open views of the universe’s first stars and galaxies, probe the atmospheres of planets around other stars—and launch another revolution. “James Webb will blow the lid off everything,” says exoplanet hunter Sasha Hinkley of the University of Exeter.
Webb’s mirror has more than five times the light-gathering power of the 31-year-old Hubble Space Telescope. Unlike Hubble, Webb will work in the infrared, allowing it to see the heavily “redshifted” light of distant objects and peer through clouds of obscuring dust. It will also be able to sift exoplanet atmospheres for gases whose infrared fingerprints are mostly off-limits to ground-based observatories. “We’ve never looked at the universe at these wavelengths and these depths and resolution,” says Steve Finkelstein of the University of Texas, Austin, who will lead several projects looking at distant galaxies in Webb’s first year. “I think we’ll be in for some surprises.”
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