Black holes are formed either by the collapse of a massive star or by the merger of heavy objects. However, scientists suspect that smaller “primordial” black holes, including some with masses similar to the Earth, may have formed in the chaotic early moments of the universe. When we think of black holes, we tend to picture enormous cosmic monsters, such as stellar-mass black holes with masses tens or hundreds of times that of the Sun. We can even imagine supermassive black holes, with masses millions (or even billions) of times that of the Sun, sitting at the hearts of galaxies and dominating their surroundings. A team of scientists has predicted that NASA’s Nancy Grace Roman Space Telescope could detect a class of “light” black holes that have eluded detection until now.