Quantum effect evident in space near neutron star

A quantum effect predicted decades ago appears to be affecting light passing through the space around a neutron star.

A prediction made 80 years ago regarding a quantum distortion effect might be finding its first evidence in observations of empty space near a neutron star.

Phys.Org explains that a quantum effect called vacuum birefringence may have been observed near a neutron star called RX J1856.5-3754.  Scientists observed the light coming from the highly magnetized star using ESO’s Very Large Telescope (VLT).  The polarization of the light as it passed through empty space near the star suggest that vacuum birefringence is at play.

The star in question lies about 400 light-years from Earth, making it one of the closest neutron stars to our solar system.  Neutron stars are extremely dense and have very strong magnetic fields which can be billions of times stronger than the Sun’s magnetic field.  The fields are sufficiently strong to affect the empty space surrounding them.

The vacuum of space, as surrounds RX J1856.5-3754, is generally considered empty, such that light can travel unchanged through the vacuum.  Quantum electrodynamic (QED) theories hold that this empty space actually contains virtual particles that constantly flash in and out of existence.  A strong magnetic field, such as that of a neutron star, is thought to be able to interact with the quantum particles and thus affect the polarization of any light passing through the area.

“According to QED, a highly magnetized vacuum behaves as a prism for the propagation of light, an effect known as vacuum birefringence,” Roberto Mignani of INAF Milan said.

Scientists have not yet successfully demonstrated this quantum effect in lab experiments.

“This effect can be detected only in the presence of enormously strong magnetic fields, such as those around neutron stars. This shows, once more, that neutron stars are invaluable laboratories in which to study the fundamental laws of nature,” Roberto Turolla of the University of Padua said.

The researchers found evidence of linear polarization of the star’s light, hinting that the quantum effect is taking place near RX J1856.5-3754.

“The high linear polarization that we measured with the VLT can’t be easily explained by our models unless the vacuum birefringence effects predicted by QED are included,” Mignani said.  “Polarization measurements with the next generation of telescopes, such as ESO’s European Extremely Large Telescope, could play a crucial role in testing QED predictions of vacuum birefringence effects around many more neutron stars.”

The study will appear in Monthly Notices of the Royal Astronomical Society.