James Webb Space Telescope’s first deep-field image is stunning

NASA’s James Webb Space Telescope (JWST) has revealed galaxies we have never been able to see before. The first deep-field image from the telescope was released on 11 July and is zoomed in further than any previous infrared picture we have taken of the cosmos. But the record won’t stand for long, as the telescope continues to push the limits of astronomical observation. Four more images are scheduled to be released on 12 July.

JWST launched from French Guiana at the end of 2021 and arrived in its final orbit around the sun in early 2022. Images with high enough quality to use for science have now started to beam down to Earth. In a press conference at the White House on 11 July, US president Joe Biden announced the first of these images.

The image shows a region of space called SMACS 0723, which contains what astronomers call a gravitational lens. In areas like this, a massive object relatively close to Earth behaves like a magnifying glass, distorting space and stretching the light of anything behind it.

The gravitational lens in SMACS 0723 is particularly strong because the nearby object distorting space-time isn’t one galaxy, but a large cluster of galaxies.

The small specks and streaks of light amplified by the lens and visible around the edges of the image are distant, incredibly faint galaxies – some of the first that ever formed.

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We couldn’t see these galaxies before now. That is partly because of the expansion of the universe: the further away an object is, the faster it is moving away from us and the redder its light appears because of that motion. JWST can spot these because it uses infrared light, allowing it to see objects that appear so red that they have become invisible to its predecessor, the Hubble Space Telescope, which observes light mainly in visible wavelengths.

Being able to see so deeply into the universe – and thus far back in time – will help astronomers understand the earliest stars. “We think that when stars form from primordial material in the distant universe, they form in a very different way, but we’ve never really observed that before,” says Stephen Wilkins at the University of Sussex in the UK. “There’s a lot of crucial physics there that we don’t know anything about.”

Understanding the formation of these early stars and galaxies could also help solve the mystery of how the seeds of supermassive black holes form.

This first image is a tantalising hint of what is to come from JWST, in the form of both more pictures and detailed observations of the universe. In the coming weeks, the floodgates of JWST science are set to open and transform our understanding of the cosmos.

“All the data we’ve seen before now has just shown that it’s actually working – but the data today and tomorrow is the first data that we can potentially do science on, and very soon we’ll get data that we can definitely do science on,” says Wilkins.

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