Astronomers may have obtained the most compelling evidence for one of the strangest predictions of quantum mechanics: that even "empty" space can influence the propagation of light.
This concerns vacuum birefringence, an effect predicted nearly 90 years ago by Werner Heisenberg. According to the theory, an ideal vacuum is not empty: virtual particles are constantly being born and disappearing within it, and in an ultra-strong magnetic field, they can alter the polarization of light.
Researchers from an international team, including Dr. Marcus Lower from Swinburne University, studied the magnetar 1E 1547.0-5408—a neutron star with a magnetic field trillions of times stronger than Earth's. Observations were conducted using NASA's IXPE X-ray polarimeter, the NICER telescope on the ISS, and the Australian Murriyang radio telescope.
Radio observations showed that the magnetar's magnetic and rotation axes almost coincide, and the observer sees it almost "from the pole." Such geometry is perfectly suited for detecting the effect.
IXPE X-ray data revealed an extremely high degree of polarization, with the direction of polarization clearly following the star's magnetic field—exactly as should happen with vacuum birefringence.
"To detect the effect, you need a field 100 million times stronger than any we can create on Earth. Nature has given us magnetars—ideal cosmic laboratories," noted Dr. Lower.
The results were published in the journal Nature. If the interpretation is confirmed, this will be the first direct evidence of a phenomenon predicted back in the 1930s.
Additional observations and more precise models will help separate the quantum signal from other processes around the magnetar. What does this mean for our understanding of the fundamental nature of space?
The discovery opens a new path to studying the quantum vacuum in the most extreme conditions of the Universe.
