ObserveTheSky › Everything in the sky › The James Webb Space Telescope
spacecraft · Sun-Earth L2 point, 1.5 million km beyond Earth

The James Webb Space Telescope compared to a school bus

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

Can you see it?

No small telescope will show you this one; it is here to be understood, not spotted.

How big is the James Webb Space Telescope compared to a school bus?

The James Webb Space Telescope is roughly one and three quarters times as long as a school bus.

How far away is the James Webb Space Telescope from Earth compared to the Earth-to-Moon distance?

The James Webb Space Telescope sits about four times the Earth-to-Moon distance from Earth.

How long does the James Webb Space Telescope take to loop once round L2?

The James Webb Space Telescope takes about 6 months to go once round L2.

How much mass does the James Webb Space Telescope have compared to a school bus?

The James Webb Space Telescope has roughly half the mass of a school bus.

Worth knowing about the James Webb Space Telescope

Its size: primary mirror 6.5 m across, 18 hexagonal segments; sunshield 21.2 m × 14.16 m, five layers each thinner than a human hair. Light crosses from Earth to the James Webb Space Telescope in 5.003 seconds.

Why it stands out
Launched 25 December 2021, then spent about two weeks unfolding itself in space — hundreds of single points of failure (including the sunshield) all had to work perfectly. The sunshield keeps it at around −233 °C (40 K), cold enough to catch the faint infrared glow of galaxies whose light has been stretching redder for over 13 billion years — and to see them is to look back in time towards the early universe. Named after James E. Webb, a former NASA administrator. The spot it sits in is one of five places where the Sun’s and the Earth’s pulls together keep a spacecraft in step with the Earth, so it can hold station without burning much fuel.
How it moves
Loops in a halo orbit around the L2 Lagrange point while L2 itself travels with Earth around the Sun once a year.
The mission
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.
The James Webb Space Telescope — Rendered from NASA’s model, not photographed.
The numbers
Longest dimension21.2 m
Distance from Earth1.5 million km
Once round its loop about L2about 180 days

How anyone knows this

We know where it is because we track it.

Games it appears in

Show the James Webb Space Telescope in the model☀️ Everything the Sun holds🌙 Plan an evening outside