COVER: ANDY POTTS THIS PAGE: GETTY IMAGES X2, BBC, DANIEL BRIGHT

It finally happened. The James Webb Space Telescope (JWST) revealed its first image… after a short wait. The project took nearly 20 years to build and cost $10bn, making it one of the more expensive missions in recent history.

The image is, of course, astonishing. Take a grain of sand and hold it up at arm’s length – that’s the portion of sky the image covers. It’s what’s known as a deep-field image (essentially a long-exposure photo that tries to pick up the faintest, most-distant objects). But what’s really cool about it is that the JWST, our most powerful telescope, is actually looking through another hugely powerful telescope, one that’s created by a natural phenomenon. To be precise, the image shows a massive galaxy cluster named SMACS 0723 as it appeared 4.6 billion years ago. There’s so much mass in this portion of space that it’s warping space-time into a lens, bending and focusing light towards the sensor aboard the JWST. In effect, it’s a telescope formed by gravity. You can see the warping in the shape of some of the galaxies – they look stretched and curved. These galaxies are actually behind the cluster in the centre.