The discoveries were made by sifting through several years' worth of data gathered by the Dark Energy Survey (DES), and applying new techniques to study objects that the survey was never intended to search for.

While Neptune is the furthest known planet in the solar system (sorry Pluto), that doesn't mean there's nothing beyond it. Roughly 3,000 trans-Neptunian objects (TNOs) are known to be drifting around even further out, ranging from small asteroids and comets right up to dwarf planets like Pluto. There's even a chance that larger undiscovered planets are hiding in these distant shadows.

And now that known TNO population has grown, thanks to a project that wasn't specifically designed to look for them. The goal of DES is to study the mysterious force that drives the acceleration of the expansion of the universe, and it does this by studying galaxies and supernovae with an extremely wide field of view.

After six years of staring at the sky, DES had plenty of data for astronomers to pore over. For the new study, scientists at the University of Pennsylvania took the first four years of that data and applied new analysis techniques to allow objects moving across the sky to be spotted.