As a pulsar rotates, it emits a beam of electromagnetic radiation, sort of like light coming from a lighthouse. Scientists use radio telescopes that pick up on the pulses coming from the star. But as scientists watched J1906, the pulsar began to slip off the radar. It seems that as the pulsar spins around its companion star, the mass of the companion star makes it sink into a dip in space-time, so that its radio waves can no longer reach Earth. The concept is called geodetic precession, which, according to NASA, uses Einstein's theory of relativity to understand how massive objects like the Earth curve the space around them, influencing the local space-time fabric.