Andrzej Udalski

In the darkness of interstellar space drift millions of rogue planets — worlds not bound to any star. They are almost impossible to see, but when such a wanderer passes in front of a distant star, its gravity bends the light and momentarily creates a cosmic magnifying glass.

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.