An international research team has found the first hints of “vacuum birefringence” around an extremely magnetic neutron star – a quantum effect Werner Heisenberg predicted nearly 90 years ago. Even seemingly empty space, it turns out, affects how light travels.
What Heisenberg predicted
According to quantum electrodynamics, a “perfect vacuum” is not truly empty but filled with virtual particles that constantly pop in and out of existence. In extremely strong magnetic fields, these should make the vacuum optically active – “birefringent” for the light passing through. On Earth the effect is far too weak to measure; a magnetar with its gigantic magnetic field provides the cosmic laboratory for it.
The evidence
The team observed the magnetar 1E 1547.0–5408 with NASA’s IXPE X-ray telescope, supported by the NICER instrument on the ISS and CSIRO’s Parkes radio telescope. Two signatures point to the effect: the X-rays were extremely highly polarized, and the polarization direction was “locked” to the star’s magnetic field – just like the radio waves. The results were published in the journal Nature.
Sources: Nature, ScienceDaily.
