A Magnetar’s Light Just Revealed Signs of a Quantum Effect Predicted 90 Years Ago

A magnetar — a neutron star with the most extreme magnetic field known in the universe — has apparently done what no laboratory could: revealed signs of a quantum effect that Werner Heisenberg predicted nearly 90 years ago. Its light shows hints that what we call empty space is not empty at all.

Heisenberg’s theory, worked out in the 1930s, says that a magnetic field strong enough should change the properties of the vacuum itself. Quantum mechanics insists that empty space seethes with virtual particles popping in and out of existence, and a truly colossal magnetic field should interact with that seething sea — subtly altering how light travels through it.

Why only a magnetar can do this

The fields required are almost unimaginable. A magnetar’s magnetic field can be a thousand trillion times stronger than Earth’s — the strongest known in nature. Build a magnet that strong on Earth and it would tear itself apart instantly. So when astronomers studied light from a magnetar and found signs that it was being modified in ways ordinary physics cannot explain, it pointed directly at Heisenberg’s old prediction: vacuum birefringence, the polarization of empty space by magnetism.

What it means

If confirmed, the observation would extend quantum theory into a regime it has never been tested in — the magnetic fields around dead stars — and confirm that the quantum vacuum behaves as theory says even under nature’s most brutal conditions. It is a reminder that some of physics’ deepest ideas find their testing grounds not in laboratories, but in the leftover wreckage of exploded stars, light-years away.

Featured image: artist’s impression of the magnetar in star cluster Westerlund 1, ESO/L. Calçada (CC BY 4.0). Source: ScienceDaily.