Hubble caught a lift to orbit tucked inside NASA's space shuttle Discovery in 1990. It quickly ran into trouble: one of the telescope's solar wings jammed as it was unfurling.
Webb is expected to behold light from the universe's first stars and galaxies, beyond Hubble's range. This light will reveal how the original stars looked 13.7 billion years ago. Hubble has stared as far back as 13.4 billion years, disclosing a clumpy runt of a galaxy that is currently the oldest and farthest object ever observed.
Astronomers are eager to close the 300 million year gap with Webb and draw ever closer in time to the Big Bang, the moment the universe formed 13.8 billion years ago.
What's the difference in how the telescopes see the universe?
Hubble sees what we see — visible light — with a little ultraviolet and infrared thrown in. Webb has infrared vision, allowing it to pierce cosmic clouds of dust.
To discern the universe's first, faint stars, Webb requires the largest mirror ever launched for astronomy. The mirror spans more than 21 feet (6.5 meters), yet is lighter than Hubble's, which is 8 feet (2.4 meters) across.
Hubble circles 330 miles (530 kilometers) overhead. The altitude was dictated by the capabilities of NASA's space shuttles, which delivered Hubble to orbit and then made five service calls.
Astronomer Edwin Hubble confirmed a century ago that countless galaxies exist beyond our Milky Way and the universe is constantly expanding. James Webb led NASA from 1961 to 1968, presiding over Projects Mercury and Gemini, and the early phase of Apollo's moon-landing program.
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