First Pictures from the James Webb

The wait is finally over...
19 July 2022

Interview with 

Chris Smith


Artist's impression of the James Webb Telescope


The James Webb space telescope launched on Christmas Day last year; it reached its final position in late January about 1 million miles away. It’s at what's called a LaGrange point, which is a region of neutral gravity that makes it easy for the telescope to park itself.

The telescope mirror that collects light is about 25 square metres in area, which is at least 6 times bigger than the one carried by the Hubble telescope and means we can see far further than we've ever seen before.

And the really exciting thing about the James Webb is that it's built primarily to see infrared light, or heat.

That might sound counter-intuitive: why would we want to see heat rather than look at visible light that we normally can see with our eyes? 

The answer is that this will enable the James Webb to peer through the fog of gas and dust that spans the Universe and often obscures other colours of light, including visible light, which means that - previously - some distant parts of the Universe have been off limits to us. But because infrared can thread its way through that material fairly easily, we now have the equivalent of powerful night vision goggles that can show us what's really out there.

There's also another advantage to relying on the infrared: as the Universe has aged, it's expanded. This has had the effect of stretching the rays of light coming to us across space. This is called cosmological red-shifting. And it's most pronounced for some of the oldest - and hence earliest - galaxies that formed in the young Universe.

The light from those has been red-shifted to such an extent that it now sits in the infrared, so the James Webb is also a window back in time to what the Universe looked like perhaps just a couple of hundred million years after the Big Bang. This means we can use it to test our theories of how the Universe has evolved and grown.

And perhaps most exciting of all, because different chemicals soak up and emit unique colours of light, by watching as distant planets float past in front of their parent stars, we'll be able to see - from the colours of the light they block out - what the atmosphere is made of on those distant worlds. We'll be able to find would-be Earth's - and discover how common our world is - in the grand scheme of things.

It’s certainly a very exciting time, and the word from NASA is, predictably, watch this space!


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