The Webb telescope begins its million-mile journey

The James Webb Space Telescope launched today aboard an Ariane 5 rocket from French Guiana. After separating from the rocket, the observatory deployed its solar array and began traveling toward an orbit roughly one million miles from Earth.

Webb carries a segmented 6.5-meter primary mirror and instruments designed mainly for infrared observation. A five-layer sunshield must keep them cold, but both mirror and shield were folded to fit inside the rocket and now require a carefully sequenced deployment.

The launch removes one risk and begins weeks of others. Engineers cannot visit the distant observatory for a simple repair, so motors, latches and cables must work as planned before months of cooling and calibration. If commissioning succeeds, astronomers expect to study early galaxies, forming stars and the atmospheres of planets around other suns. For now, the achievement is an intricate machine safely in flight, with its most complicated transformation still ahead.