Observations of the dense remnant of an exploded star have provided the first sign of a quantum effect on light passing through empty space.

Light from the stellar remnant, a neutron star located about 400 light-years away, is polarized, meaning that its electromagnetic waves are oriented preferentially in a particular direction like light that reflects off the surface of water (SN: 7/8/06, p. 24). That polarization is evidence of “vacuum birefringence,” a quantum effect first predicted 80 years ago caused by light interacting with the vacuum of space in a strong magnetic field. Scientists report the result in a paper to be published in the Feb. 11, 2017 issue of Monthly Notices of the Royal Astronomical Society.

“It’s the most natural explanation,” says astrophysicist Jeremy Heyl of the University of British Columbia in Vancouver, who was not involved with the new result. But he cautions, other sources of polarization could mimic the effect, and additional observations are necessary.

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