Pulses from neutron star (rear) are slowed as they pass near foreground white dwarf. This effect is known as the Shapiro Delay, allowed astronomers to measure masses of the system. This pulsar, called PSR J1614-2230, spins 317 times per second, and the companion completes an orbit in just under nine days. The pair, some 3,000 light-years distant, are in an orbit seen almost exactly edge-on from Earth. That orientation was the key to making the mass measurement.