The James Webb Space telescope will image the little-known places in the Milky Way and beyond. Here are just a few of the things it hopes to see and the tech it will use to see them.
JWST: The facts
Full name: James Webb Space Telescope
Size: 21 x 14m (sunshield)
Launch mass: 6,200kg
Cost to build: $10bn
Launch date: 31 October 2021
Expected first images: 2-3 months after launch
Collaborators: NASA, ESA and Canadian Space Agency
Mission duration: 5-10 years
Orbit: 1.5 million km from Earth
The James Webb Space Telescope’s tech
1: Secondary mirror
Reflects light from the primary mirror and focuses it into the Integrated Science Instrument Module (ISIM).
2: Primary mirror
18 hexagonal segments, coated with gold, capture the light from distant celestial objects.
The size of a tennis court, it protects the telescope from light sources, such as the Sun.
The Integrated Science Instrument Module produces images from light captured by secondary mirror.
2: Spacecraft bus
Contains most of the steering and control machinery.
3: Star trackers
Small telescopes that observe star patterns to help aim the telescope.
4: High gain antenna
Transmits data back to Earth and receives commands from NASA’s Deep Space Network.
What will the JWST see?
The early Universe
The JWST will be able to look back to around 200 million years after the Big Bang, when the first stars in the Universe formed.
The first stars are thought to have been massive giants made of hydrogen and helium, whose short lives ended in the supernovae that created the heavier elements we detect in younger stars today. To see this period in cosmic history, we need sensitive infrared instruments to detect the faint traces of light that have travelled through space and time to reach us.
The JWST will also look back to the very first galaxies in the Universe to learn more about their evolution and why there’s so much variety in them. Nearly all the spiral and elliptical galaxies that we see today have experienced at least one collision or merger with another local galaxy.
Yet older galaxies look entirely different to their modern counterparts – smaller, clumpier, less structured. Examining galaxies can also inform us of the macrostructure of the Universe and how it’s organised on a large scale.
Dark matter is thought to play an important role in the structure of the Universe, accounting for five times the mass of normal, baryonic matter such as atoms and particles. Considered to be the scaffolding for the Universe, we’re only able to observe dark matter indirectly by measuring how its gravity affects stars and galaxies.
The JWST won’t be able to see dark matter, but it will employ gravitational lensing techniques to study the most distant galaxies and look at their rotation for signs that dark matter is at play.
The JWST will help answer the big question of whether life exists beyond Earth by studying a variety of exoplanets – planets outside our Solar System.
Of particular interest is the TRAPPIST-1 system, where three of its seven planets are in the habitable zone and one may harbour liquid water. The JWST will observe the planet as light from its parent star passes through the planet’s atmosphere, revealing its chemical composition and the gases that are present there.
Our ice giants
While the JWST’s primary science aims lie more in cosmology and star formation, it’ll also take a closer look at a couple of familiar objects – our ice giants, Neptune and Uranus.
The JWST will map their atmospheric temperatures and chemical composition to see how different they are – not only to each other, but also their gas giant cousins, Jupiter and Saturn. The ice giants are at least 30 times further from the Sun than Earth and are the least understood planets in our Solar System.
Pluto and the Kuiper Belt Objects
Dwarf planet Pluto and its fellow Kuiper Belt Objects will also be receiving some observation time.
The JWST is powerful enough to study such icy bodies including comets, which are often-pristine leftovers from our Solar System’s days of planet formation and could hold clues to Earth’s origins. There are no planned missions dedicated to the outer Solar System for years, so new observations and data will play a big part in planning for future planetary missions.