
The observation came after a decade-long quest, years earlier than expected, and was described by one excited observer as the biggest astronomical breakthrough since the Nobel-capped detection of gravitational waves in 2015.
Using data from a NASA X-ray laboratory in space, Xinyu Dai, an astrophysicist and professor at the University of Oklahoma, 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, our solar system's biggest planet.
There are few methods to determine the existence of distant planets. They are so far away that no telescope can observe them, Dai told The Washington Post. So Dai and his postdoctoral researcher Eduardo Guerras relied on a scientific principle to make the discovery: Albert Einstein's Theory of Relativity.