The gravitational lensing that causes this rare phenomenon cannot be explained solely by looking at observable objects—suggesting that dark matter had a hand in its formation.

A paper on HerS-3:

https://iopscience.iop.org/article/10.3847/1538-4357/adf204

“Detailed 1 mm spectroscopy and imaging with NOEMA and the Atacama Large Millimeter/submillimeter Array resolve the individual images and show that each of the five images display a series of molecular lines that have similar central velocities, unambiguously confirming that they have identical redshifts.”