The beam structure of a pulsar has been determined for the first time in a 14-year study of a binary pulsar. The observations match predictions of relativity theory about how the spin axes of each pulsar should change direction with time. Image: Gregory Desvignes and Michael Kramer, MPIfR
Pulsars are fast-spinning neutron stars that concentrate 40 percent more mass than the Sun – or more! – into a small sphere of only about 20 kilometres (12 miles) diameter. They have extremely strong magnetic fields and emit a beam of radio waves along their magnetic axes above each of their opposite magnetic poles.
Due to their stable rotation, a lighthouse effect produces pulsed signals that arrive on Earth with the accuracy of an atomic clock. The large mass, the compactness of the source, and the clock-like properties allows astronomers to use them as laboratories to test Einstein’s general theory of relativity.
The theory predicts that spacetime is curved by massive bodies such as pulsars. One expected consequence is the effect of relativistic spin precession in binary pulsars. The effect arises from a misalignment of the spin vector of each pulsar with respect to the total angular momentum vector of the binary ...