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stormwyrm [soylentnews.org] writes:

In 1936, Werner Heisenberg and Hans Euler predicted that thanks to the Uncertainty Principle that bears Heisenberg’s name, what we think of as ‘empty’ space must be really be filled with virtual particle-antiparticle pairs that pop in and out of existence so rapidly that they can’t be directly observed. They predicted, however, that because of these virtual particles, a very strong magnetic field should affect the way light propagates through otherwise empty space. This phenomenon, known as vacuum birefringence, was long theorised but was only recently observed directly from the faint neutron star RX J1856.5-3754, which exhibits an extremely powerful magnetic field in the gigatesla range but also lacks the dense plasma-filled magnetosphere that typically surrounds most other neutron stars, which make observing the effect impossible. A team of scientists led by Roberto Mignani, using the Very Large Telescope in Chile, was able to measure the polarisation of the light from the neutron star and confirm the predictions of Heisenberg and Euler. From the abstract:

The “Magnificent Seven” (M7) are a group of radio-quiet Isolated Neutron Stars (INSs) discovered in the soft X-rays through their purely thermal surface emission. Owing to the large inferred magnetic fields (B ≈ 10¹³ G), radiation from these sources is expected to be substantially polarised, independently on the mechanism actually responsible for the thermal emission. A large observed polarisation degree is, however, expected only if quantum-electrodynamics (QED) polarisation effects are present in the magnetised vacuum around the star. The detection of a strongly linearly polarised signal would therefore provide the first observational evidence of QED effects in the strong-field regime[…]The [polarisation degree] that we derive is large enough to support the presence of vacuum birefringence, as predicted by QED.

Evidence for vacuum birefringence from the first optical polarimetry measurement of the isolated neutron star RX J1856.5−3754 [eso.org]. Mon. Not. R. Astron. Soc. 465, 492 (2016); DOI: 10.1093/mnras/stw2798 [doi.org].

Further comment from astrophysicist Ethan Siegel [forbes.com] (archive.is link [archive.is]).

Original Submission