A team of astronomers recently identified a red giant star with an unseen binary companion after examining data from the Large Sky Area MultiObject Fiber Spectroscopic Telescope (LAMOST) and the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Although the companion object can’t be observed visually, astronomers can see the gravitational effects it has on the red giant star.

All of this is nothing new—researchers often discover binary systems with effectively invisible companions thanks to gravitational effects. However, the inferred mass of the unseen object, along with the system’s other characteristics, makes it a bit of an anomaly. The research on this pair, published in Science Advances, suggests the unseen companion is likely an unusually massive neutron star that is pushing the boundaries of how massive neutron stars can get.