How the James Webb Space Telescope works

Key points

• The telescope is built to catch infrared light that has been stretched by the expanding universe, light from the first stars and galaxies that is otherwise too faint or invisible from Earth. 1:17
• Four instruments split the work: NIRCam takes primary images, NIRSpec analyses light spectra, NIRISS adds imaging and spectroscopy, and MIRI sees longer infrared wavelengths that can penetrate thick dust. 2:43
• Studying a spectrum reveals an object's mass, temperature and chemical composition, and NIRSpec's micro shutter system, with 250,000 shutters, lets it take spectroscopy of hundreds of objects at once. 3:32
• MIRI must be cooled to 6.7 K (about −266.5 °C), which is why it needs a helium-based cryocooler, and a five-layer sun shield measuring 21 by 14 meters keeps heat from the Sun, Moon and Earth away from the telescope. 5:37
• The telescope cost about 10 billion dollars, took over 20 years to develop, and is positioned 1.5 million kilometers from Earth at Lagrange point 2, far beyond Hubble's 547 kilometers. 0:22

Words the video explains

• redshift — Redshift: as light from distant stars and galaxies travels and space expands, its waves lengthen and the light shifts toward infrared. 1:39
• coronagraph — A coronagraph blocks bright light so that fainter objects nearby become visible, following the same principle as blocking the sun with your hand. 3:07
• spectroscopy — By studying the spectrum of light emitted by an object, scientists can determine its mass, temperature and chemical composition. 3:32
• micro shutter system — A new technology developed for NIRSpec that uses many tiny shutters to select which light reaches the spectrograph. 4:03
• cryocooler — The cryocooler is an additional cooling system that scientists developed for MIRI. 5:46
• Lagrange point 2 (L2) — Lagrange point 2 is one of five places in the solar system where gravitational forces let objects stay in a fixed position relative to Earth. 7:00
• Infrared — Light the telescope sees; it can penetrate dust clouds that block visible light. 1:09
• Spectrum — Light split by an object, whose black lines reveal its mass, temperature and chemical composition. 3:32
• Micro-shutter system — 250,000 shutters that open and close to let light from chosen objects through, blocking irrelevant light. 4:03
• Lagrange point 2 — One of five places where gravity lets an object hold a fixed position relative to Earth. 7:00

The video's claims and reasons

• The James Webb Space Telescope is about 100 times more powerful than Hubble. 1:00
• Infrared light can penetrate dust clouds, letting the telescope see forming stars. 1:17
• The mirror folds for launch and is aligned in space to focus light. 2:02
• Micro-shutters let the telescope study hundreds of objects at once. 3:55
• MIRI needs a cryocooler and a sun shield to stay cold enough. 5:46
• The telescope will orbit at Lagrange point 2, far beyond Hubble. 6:43
• The telescope could help explain planetary rings and exoplanet atmospheres. 8:17

Details worth a second look

• Hexagonal primary mirror — The gold hexagonal mirror segments form the telescope's light-collecting dish above a grey sun shield.
• 1.32-meter hexagon — A single hexagonal mirror segment is drawn with a dashed diagonal and labelled 1.32 meters.
• Temperature readout — Two labels show -266.5 degrees Celsius and -447.61 degrees Fahrenheit beside the telescope.
• Five sun shield layers — Five stacked grey layers with red glow between them illustrate the sun shield's passive cooling.
• TRAPPIST-1 planets — A label reads TRAPPIST-1 above planets marked C, E, F, G and H with a light curve below.

Questions to check yourself