James Webb Space Telescope

Infrared space telescope parked far beyond the Moon at the Sun-Earth L2 point, built to see the first galaxies and planets being born.

Also called: JWST, the Webb telescope.

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What it is

Spacecraft: Ours. The only things on this list we made. Every kind of thing there is →

Can you see it?

No. No telescope on Earth will show you this one; it is here to be understood, not seen. It is here because it is worth knowing about — and because leaving it out would make the sky look emptier than it is.

Worth knowing about the James Webb Space Telescope

The James Webb Space Telescope is built around a gold-coated mirror as wide as a three-story building is tall, with a sunshield that unfolds to about the size of a tennis court. In weight, about as heavy as a school bus. Light crosses from Earth to the James Webb Space Telescope in 5 seconds.

How it moves: Doesn't circle Earth like the Moon or the ISS. Instead it rides along with Earth around the Sun, parked at a spot called the Sun-Earth L2 point, about four times farther away than the Moon -- always on Earth's night side, so its huge sunshield can block the Sun, Earth and Moon all at once and keep its instruments deep-freeze cold.
The machines we sent: A NASA/ESA/CSA infrared telescope, successor to Hubble, built to see the first galaxies to form after the Big Bang, watch stars and planets being born inside dusty clouds, and study the atmospheres of planets orbiting other stars.
What makes it worth knowing: Launched December 25, 2021, then spent about two weeks unfolding itself in space -- hundreds of single points of failure (including the tennis-court-sized sunshield) all had to work perfectly. Staying this cold (around -233C / 40 K) lets it catch the faint infrared glow of galaxies whose light has been stretching redder for over 13 billion years, effectively looking back in time toward the early universe. Named after James E. Webb, a former NASA administrator. The spot it sits in is one of five places where the pull of the Sun and the Earth balance out so a spacecraft can hold station without burning much fuel -- [what a Lagrange point is](lagrange.html).

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