John Mather knows what it is like to be Galileo. The Italian scientist saw a new world of mountains on the Moon and satellites in orbit around Jupiter when he turned the most powerful telescope of his day on the heavens in 1610. In the past six months, Mather has glimpsed a new world of galaxies and stars beyond anything seen before with the most powerful telescope of our own day: Nasa’s James Webb Space Telescope. “I never expected to see individual stars in the dawn of time,” he tells me over video call. “The telescope has far exceeded our expectations and we are beyond ecstatic.”
The successor of Nasa’s Hubble Space Telescope, the James Webb was launched on Christmas Day 2021. With its 6.5-metre mirror made of 18 hexagonal segments, it is floating around the “Lagrange-2” point, 1.5m kilometres from Earth, shielded from solar heat by a tennis-court-sized sunshade.