Finally, scientists have their finger on the pulse.
Spinning dead stars, known as pulsars, blast powerful beams of radio waves into space. As a pulsar spins, its beams sweep past Earth, producing a pulsating signal similar to a lighthouse’s flashes. Astronomers now have mapped the structure of the beams of one pulsar, using observations made over decades. The technique relies on Albert Einstein’s theory of gravity, general relativity, and simultaneously reconfirms that the theory is correct, the scientists report in the Sept. 6 Science.
The result allowed researchers to “view the beam of a pulsar in a whole new way,” says astrophysicist Victoria Kaspi of McGill University in Montreal, who was not involved with the new study.
Pulsars are a type of neutron star, a dense remnant left behind when a star explodes. Powerful magnetic fields direct radio waves from a pulsar outward in beams. Typically, those beams pass by Earth at a fixed angle, and scientists can glimpse only a single slice through a beam as it rotates — like viewing a lighthouse beacon through a tiny slit.
But the newly mapped pulsar, known as PSR J1906+0746, was unusual: It was part of a duo, orbiting with another neutron star, about 20,000 light-years away from Earth (SN: 12/18/15). According to general relativity, if a pulsar spins at an angle misaligned with the pair’s orbit — which this one does — the pulsar will precess. That means that the axis on which the pulsar is spinning rotates, much like a wobbling top.