Astronomers are using pulsars to spot gravitational waves

Earlier this month scientists detected gravitational waves, but it wasn't easy. Because of the tiny forces involved, it took us nearly 100 years to confirm Einstein's original prediction that ultra-massive objects like black holes could send ripples across space-time. A team of astronomers from a group called NANOGrav thinks it can use stable pulsar signals to track tiny movements in the Earth when it's jostled by gravitational waves. "Detecting this signal is possible if we are able to monitor a sufficiently large number of pulsars spread across the sky," says Stephen Taylor from NASA's Jet Propulsion Laboratory. "The smoking gun will be seeing the same pattern of deviations in all of them."

Pulsars are spinning, highly magnetized neutron stars that are left after stars go supernova. Some spin thousands of times per second, sending a signal to Earth on each rotation. "Millisecond pulsars have extremely predictable arrival times, and our instruments are able to measure them to within a ten-millionth of a second," says NANOGrav's Maura McLaughlin. "Because of that, we can use them to detect incredibly small shifts in Earth's position."

Right now the team is monitoring 54 pulsars, but most of them are in the northern hemisphere. As such, it is enlisting the help of teams in Europe and Australia "in order to get the all-sky coverage this search requires," says JPL's Michele Vallisneri. Once that happens, the team is confident they'll see evidence of low-frequency gravitational waves within 10 years. Meanwhile, a space mission called eLISA that can detect higher-frequency waves is scheduled to launch around 2028, so by then, they may be old hat.