Przemek Mróz

One night, a star at the edge of the sky suddenly flickered and brightened for a few days. It wasn't a supernova, and no cloud passed by — an invisible planet drifted between the star and Earth. Its gravity bent the light of the distant star like a pair of glasses focusing a sunbeam.

For nearly a century, astronomers have been searching for dark matter — an invisible scaffold that keeps galaxies from flying apart. Fritz Zwicky first proposed it, and Vera Rubin proved its existence by showing that stars on the outskirts of galaxies move too fast.

In the Galactic bulge, where the light of billions of stars merges into a continuous glow, four cold giants passed unnoticed. You can't see them through a telescope — too far, too dim.