The James Webb Space Telescope (JWST) is one of the most remarkable machines humans have ever built. 🔭✨ It is often described as the successor to Hubble, but it isn't simply a newer Hubble. Webb was designed to see a different part of the universe in a very different way.Webb was launched on December 25, 2021, aboard an Ariane 5 rocket from French Guiana. It is a joint project involving NASA, the European Space Agency and the Canadian Space Agency. Canada contributed the Fine Guidance Sensor and the NIRISS scientific instrument, as well as other technology and expertise.
Why does Webb look so strange?
That enormous golden honeycomb is its primary mirror. It consists of 18 hexagonal segments, made primarily of lightweight beryllium and coated with an extremely thin layer of gold.
The mirror is about 6.5 metres across and has a collecting area of roughly 25 square metres. The gold isn't there because NASA wanted a fancy-looking telescope — gold is highly effective at reflecting infrared light, which is what Webb is designed to detect.
And here's the amazing engineering trick:
The telescope had to fold up to fit inside the rocket.
The mirror segments folded inward and the enormous sunshield was packed up like an enormous piece of origami. After launch, Webb performed a complicated sequence of deployments and unfolded itself in space.
The giant sunshield ☀️
That silver-coloured structure underneath the mirror is a five-layer sunshield about the size of a tennis court.
This is absolutely critical.
Webb is an infrared telescope, and heat itself produces infrared radiation. If the telescope became warm, its own heat would interfere with the extremely faint infrared signals coming from distant objects.
The sunshield keeps the telescope's cold side below about 50 kelvin — roughly −223°C.
The five layers don't touch one another. Heat from the Sun is progressively reduced as it travels between the layers, while the telescope radiates heat away into space.
It's rather like putting a gigantic thermal blanket between Webb and the Sun.
Webb doesn't orbit Earth
This is another fascinating difference from Hubble.
Hubble orbits Earth at roughly 560 km altitude.
Webb travels around the Sun, near the second Sun-Earth Lagrange point, L2, approximately 1.5 million kilometres from Earth.
At L2, Webb can keep the Sun, Earth and Moon generally on the same side of the spacecraft. Its sunshield can therefore block their light and heat while the telescope looks outward into deep space.
Webb actually travels in a large halo orbit around L2, rather than sitting directly on the L2 point.
And unlike Hubble, Webb is too far away for astronauts to visit and repair.
What does Webb actually see?
This is where Webb gets spectacular.
It primarily observes infrared wavelengths, including near-infrared and mid-infrared light. Its wavelength range extends from about 0.6 to 28.8 micrometres.
Why infrared?
Because infrared can reveal things that visible light can't.
For example, enormous clouds of dust can hide newly forming stars from optical telescopes. Infrared light can pass through much of that dust, allowing Webb to see what is happening inside.
And there's another incredible consequence.
Webb is looking backward in time ⏳
Light travels at a finite speed.
If a galaxy is 10 billion light-years away, the light Webb receives today left that galaxy roughly 10 billion years ago.
So when Webb looks at extremely distant galaxies, it is effectively looking into the ancient universe.
Webb is designed to detect light from galaxies that formed more than 13.5 billion years ago, helping scientists investigate the earliest stages of galaxy formation after the Big Bang.
It's almost like having a telescope that doubles as a time machine.
Not because it physically travels through time — but because looking farther away means looking further into the past.
Webb has four major scientific instruments
Its instruments include:
And here's one of my favourite Webb facts...
NASA says Webb is sensitive enough that, under the right conditions, it could theoretically detect the heat signature of a bumblebee at the distance of the Moon. 🐝🌕
That's an illustration of just how incredibly sensitive the telescope is.
But perhaps the most amazing thing about Webb isn't any single photograph.
It's that this enormous, incredibly delicate observatory was launched folded inside a rocket, travelled about 1.5 million kilometres from Earth, unfolded itself in space, aligned 18 individual mirror segments to extraordinary precision, cooled itself to extremely low temperatures, and then began detecting photons that had been travelling through space for billions of years.
Every time Webb produces an image of an ancient galaxy, we're essentially seeing ancient light finally arriving at a telescope made by humans.
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