Empty space is not as empty as it seems. That’s the conclusion of a new study that examines signals from a dead star and offers what researchers say is the strongest evidence yet that extreme magnetic fields can alter the properties of a vacuum, making a seemingly empty space act like a prism and changing the way light travels through it. The findings, led by Rachael Stewart, a graduate student in physics at George Washington University, confirm a prediction of a strange effect first proposed 90 years ago. “The information we gained by looking at the core of this distant star also gives us clues about the nature of the fabric of reality as we know it, and I find that incredible,” Stewart said in a statement. The idea dates back to 1936, when German physicist Werner Heisenberg and his student Hans Euler proposed that space is never truly empty. Instead, they argued, it is a seething sea of ”virtual particles” (electrons and their antimatter counterparts, positrons) that blink in and out, briefly interacting with their surroundings before disappearing. You may like This subatomic foam is a consequence of quantum mechanics and remains invisible under normal conditions. But theory predicts that an extremely strong magnetic field, such as that surrounding a magnetar, can change the way light moves, causing light waves to align more strongly in a particular direction in an effect known as “vacuum birefringence.” “Detecting vacuum birefringence requires a magnetic field that is more than 100 million times stronger than any we have created on Earth,” co-author Marcus Lower, an astrophysicist at Swinburne University in Australia, said in another study. statement. “Fortunately, nature has provided us with magnetars, which are the perfect cosmic laboratories to search for this effect.” Magnetars are dense, city-sized remnants left after the explosion of massive stars and host the most powerful magnetic fields known in the universe. They are among the rare celestial objects capable of generating fields strong enough to reveal vacuum birefringence, offering scientists an extreme environment to test physics in conditions impossible to replicate on Earth. “We are no longer studying just astronomical objects; we are using them to test the laws of nature,” study co-author Michela Negro, an astrophysicist at Louisiana State University, said in a statement. Astronomers have glimpsed this elusive phenomenon before, but not conclusively. In 2017, researchers using Chile’s Very Large Telescope observed signs of polarization around a faint neutron star called RX J1856.5-3754, located about 400 light years from Earth. However, those optical measurements remained open to interpretation, in part due to the challenges of isolating the optical signal. What to read next An illustration of a magnetar. (Image credit: ESA) At the time, scientists noted that definitive proof would require space-based X-ray observatories, specifically NASA’s then-upcoming Imaging X-ray Polarimetry Explorer (IXPE). Launched in 2021, IXPE carries three identical telescopes designed to measure the polarization of high-energy X-rays. “Only in the last six years have we had a telescope capable of detecting this effect around magnetars,” Lower told Michael West Media, an independent news website in Australia. In March and April 2025, researchers pointed the IXPE at 1E 1547-5408, a magnetar that rotates once every two. seconds and is unusual among its kind for constantly emitting radio waves. The team supplemented that data with observations from an X-ray telescope aboard the International Space Station, as well as Australia’s Murriyang radio telescope and the South African Radio Astronomy Observatory. According to the study, two findings pointed to birefringence of the vacuum at work. First, the Second, the polarization pointed in the same direction as the star’s magnetic field, matching the pattern already observed in its radio waves. The researchers concluded that this combination leaves vacuum birefringence as the only explanation that fits the data. “It’s a bit of a relief because it means our theories still work and there’s nothing broken with the physics,” Lower told news site Michael West Media. Artistic representation of the IXPE observatory in space. (Image credit: NASA) For Fernando Camilo, chief scientist at the South African Radio Astronomy Observatory and co-author of the new paper, the discovery closes a long circle. Camilo has been studying 1E 1547-5408 since 2007, when he first detected its radio waves using the Murriyang dish, revealing its two-second rotation speed. “At the time, 1E 1547 was only the second magnetar in the Milky Way to emit radio waves, and we were confident that regular monitoring would reveal interesting behavior,” Camilo said in the statement. “However, we could never have imagined that 20 years later I would contribute to investigating a fundamental, and particularly peculiar, prediction of quantum mechanics.” The team hopes to confirm the finding with data from future missions, including a proposed orbital mission called GoSOX (short for Globe Orbiting Soft X-ray Polarimeter), along with improved computer simulations to distinguish the vacuum birefringence signal from other processes around the magnetars. “With this future data in hand and our updated simulations, we may finally be able to complete the search started by Heisenberg nearly 90 years ago,” Lower said in the Swinburne University statement. This research is described in an article published August 5 in the journal Nature.
