'It shouldn’t exist': Scientists stunned as rare 'Einstein cross' reveals mysterious fifth light

This unusual 'Einstein cross' displays light from a distant galaxy five times, instead of the typical four, creating a rare cosmic pattern. (Image: Nicolás Lira Turpaud (ALMA Observatory) & adapted from Cox et al. 2025)

Is an unseen halo of dark matter lurking in the open? A weird pattern that astronomers have spotted in a far-off galaxy, HerS-3, may unlock a secret of the cosmos. The bizarre image defies common wisdom and provides a glimpse into the mysterious realm of dark matter.

Einstein Cross Mystery Raises Questions

Why does the galaxy show five points of light rather than four? Measurements by the Northern Extended Millimeter Array in France originally hinted at a glitch in the data.

The image seemed to show an Einstein cross, where light from a distant galaxy bends around a massive foreground object. Normally, this phenomenon splits the light into four points, but a fifth glowing spot appeared in the centre. "We thought it was a problem with the instrument," said Cox, one of the researchers.

Could Dark Matter Be the Culprit?

What could explain the extra light point at the centre? Charles Keeton, a Rutgers University astronomer and study co-author, explained that a fifth image is only possible if the bending mass behaves unusually. The team ran computer models and ruled out closer objects interfering with HerS-3.

They verified the data by cross-checking it with measurements from ALMA in Chile. When they modelled a dark matter halo in front of the galaxy, the results fitted the unusual pattern to perfection.

Observing the Invisible Universe

How can researchers apply this find to learn more? Dark matter does not absorb, emit, or reflect light and so is invisible, but it does pull on things with gravity. A dark matter halo can warp light from a background galaxy without making the galaxy itself visible. Cox described the find as providing an opportunity to observe both the far-off galaxy and the unseen matter warping its light. Scientists intend to make further observations to better calibrate computational models and know how dark matter interacts with cosmic objects.