The truth is out there. And past that is a cluster of planets 3.8 billion light-years away, a discovery that could extend the boundary of what we know about the universe.

Using data from a NASA X-ray laboratory, astrophysicist Xinyu Dai detected, for the first time ever, a population of planets beyond the Milky Way galaxy. The mass of the planets range in size from Earth’s moon to the massive Jupiter.

The planets are so far away that no telescope can observe them, Dai said. So Dai and his postdoctoral researcher Eduardo Guerras relied on a scientific principle to make the discovery: Albert Einstein’s Theory of Relativity. Einstein’s theory suggests light bends when tugged by the force of gravity. In this case, the light is coming from a quasar — the nucleus of a galaxy with a swirling black hole — which emits powerful radiation.

Between that quasar and the space-based lab is the galaxy of newly discovered planets that will advance the study of planetary science. The gravitational force of the galaxy bends the light heading toward the Milky Way, illuminating the galaxy in an effect called microlensing. The technique was first used to identify planets outside of our solar system but inside the galaxy, known as exoplanets. “Microlensing is probably the only way,” Dai said. Guerras had a less formal description: “This is very cool science.”