In 2023, the James Webb Space Telescope focused on a region roughly 1,500 light‑years from Earth and captured a striking, glowing question‑mark shape against the darkness of space. While the image’s poetic appearance has captured imaginations, the underlying phenomenon is a real, measurable effect of gravity on light.
Astronomers were initially unaware of the symbol, as they were targeting two actively forming protostars in the Vela constellation. The Webb image provided the clearest view of star birth ever taken, and a small, subtle mark near the bottom of the frame—later identified as a pair of galaxies—caught the eye of observers.
The “question‑mark” is actually two galaxies within the massive cluster MACS‑J0417.5‑1154. A galaxy cluster contains hundreds or even thousands of galaxies bound together by gravity. The cluster had been imaged by the Hubble Space Telescope before, but the distinctive shape went unnoticed. Advances in instrumentation now allow us to see the subtle gravitational distortions that create this unique pattern.
Mark Garlick/science Photo Library/Getty Images
Galaxy clusters often exhibit complex arrangements of galaxies, but the MACS‑J0417.5‑1154 cluster’s structure stands out. The image makes the galaxies appear in a curved, question‑mark formation, an illusion produced by gravitational lensing—light bending around a massive object. In this case, the cluster’s immense mass warps spacetime, bending the paths of photons from background galaxies.
The main part of the question‑mark consists of two galaxies that are being lensed, creating the curved arms. The small dot at the bottom is an unwarped galaxy whose line of sight aligns with our viewpoint, placing it below the lensed pair.
