JWST begins its SCIENCE JOURNEY

As we gaze astonished at the James Webb Space Telescope’s first science images, Colin Stuart takes a look at the questions it will answer over its decade-long voyage of astronomical discovery

- Colin Stuart

Colin Stuart (@skyponderer) is an astronomy author and speaker. Get a free e-book at colinstuart.net/ ebook

A single galaxy 13.1 billion years old is picked out of a field of hundreds and its light signature recorded by Webb's NIRSpec instrument, a tool so sensitive it can mine information simultaneously from up to 150 individual galaxies that existed in the very early Universe

What do the first stars look like?

JWST will take us back to when the very first galaxies appeared

Astronomers are always looking back into the past. That's because it takes time for light to travel across the Universe. We don't see things as they are when the light arrives here, but as they were when the light first departed. For distant galaxies, the delay is millions and even billions of years.

So very distant galaxies were also some of the first galaxies to form in the Universe. The Hubble Space Telescope revolutionised this area of research, finding thousands of distant galaxies in a patch of sky so tiny that it could be covered by a grain of sand held at arm's length.

The light from the most distant galaxy observed before JWST - HD1 - took a staggering 13.1 billion years to reach Earth. Astronomers are peering back to a time just 700 million years after the Big Bang. Yet they want to look back even further to when the very first stars and galaxies appeared, estimated to be 100-200 million years after the Big Bang. They're hunting the first light that lit up the so-called cosmic dark ages.

Hubble just isn't up to that task - you need an entirely different kind of telescope. Enter JWST, which gathers infrared light instead of the visible light to which our eyes, and Hubble, are sensitive. Infrared light is able to penetrate the dust that can sometimes block our view of distant galaxies.