James Webb Space Telescope

The Webb telescope days before its launch in December 2021

Life-sized model of JWST shown at the 2007 AAS meeting in Seattle, Washington. It stands two stories high and weighs several tons. Credit: Rob Gutro, NASA/GSFC.

James Webb Space Telescope (JWST) is a telescope that was launched on 25 December 2021. It is a replacement for the Hubble Space Telescope which was launched in 1990.^[1]

The telescope is named after James E. Webb, who was a director at NASA and created the Apollo program that put astronauts on the moon.

It has a main mirror that is 6.5 metres (21 feet) wide. This is 6 times larger in area than Hubble. It is so large that it is made in 18 pieces that fold together during the launch, so that it can fit into a rocket. It is mainly an infrared telescope but also works in the red part of the visible light (the pictures will be coded with false color so we can see them). It is plated with gold because gold reflects infrared very well. It is able to see things that the Hubble Space Telescope cannot. Infrared vision can be used to see heat radiation (like some kinds of night vision goggles), so the telescope itself must be kept as cool as possible. It is protected by a large sunshield the size of a tennis court to keep it cool and dark.

NASA released the first image from JWST on 11 July 2022, the oldest and highest resolution image of the Universe.^[2]

Orbit

JWST orbit (not to scale)

The JWST is in orbit far from Earth, to avoid heat radiating from the Earth and moon. This special orbit is beyond the moon, at the second Lagrange point (L2) of the Sun-Earth system, a place of stable gravity. This orbit is 1,500,000 kilometres (930,000 miles) from Earth, about four times farther away from us than the moon.^[3] This keeps it in the Earth's shadow most of the time; it does not actually go around the Earth, but goes around the sun at the same speed as the Earth.^[4]

James Webb Space Telescope Media

Rough plot of Earth's atmospheric absorption (or opacity) to various wavelengths of electromagnetic radiation, including visible light
Test unit of the sunshield stacked and expanded at the Northrop Grumman facility in California, 2014
Engineers cleaning a test mirror with carbon dioxide snow, 2015
Main mirror assembly from the front with primary mirrors attached, November 2016
Diffraction spikes due to mirror segments and spider color-coded
Webb telescope's NIRCam, close-up*The optics module of the James Webb Space Telescope's primary imager, the Near-Infrared Camera, arrived at NASA’s Goddard Space Flight Center in Greenbelt, Md., on Saturday, July 27, 2013. This photograph shows the NIRCam optics module in a Goddard clean room.
The Calibration Assembly, one component of the NIRSpec instrument
JWSTMIRI
Diagram of the spacecraft bus. The solar panel is in green and the light purple panels are radiators.
Comparison with the Hubble Space Telescope primary mirror
Primary mirror size comparison between Webb and Hubble
Structural deployment sequence
Animation of Webb's halo orbit