According to https://www.newscientist.com/article/2328132-james-webb-spac..., "This first image is 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." and "The gravitational lens in SMACS 0723 is particularly strong because the nearby object distorting space-time is not one galaxy, but a large cluster of galaxies."