Forces powerful enough to bend light in a seething sea of electrons and positrons. The Cosmos would be made of this, a discovery made thanks to Magnetars, the hyper-magnetic stars
Last August 5, an article appeared in the journal Nature that asks one of the questions that astronomers have been asking themselves for the longest time: is space really empty? Well, observations conducted on a dead yet intensely magnetic star provide the most convincing evidence of the existence of a strange quantum effect by which empty space would alter the way light propagates.
New evidence confirms the theories
By analyzing the signals coming from that celestial body, researchers have found the most convincing evidence so far that extreme magnetic fields can alter the properties of the vacuum, causing it to behave like a sort of prism and therefore modify the way light passes through it. And the first results obtained by the scientist Rachael StewartPhD student in Physics at George Washington University, would confirm what was first hypothesized 90 years ago.
There Stewart said: “The information we have obtained by observing 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.”
Heisenberg hypothesized subatomic space
As mentioned, the intuition of this theory dates back to 1936, when the German physicist Werner Heisenberg and his student Hans Euler proposed that space is never truly empty, arguing instead that it is a seething sea of virtual particles – electrons and their antimatter counterparts, positrons – that appear and disappear, interacting briefly with their surroundings before vanishing. In short: the Cosmos, where we believe it to be devoid of matter, in addition to some vacant gas, would present a sort of subatomic foam, a consequence of quantum mechanics, which is invisible in normal conditions.
Magnetars alter the light they use
The theory predicts that an extremely strong magnetic field, such as that around a celestial body such as magnetars (from the English magnetic and star, literally magnetic star), i.e. one that has a huge magnetic field, billions of times that of the Earth with high levels of electromagnetic emissions, can modify the way in which light propagates, causing a more intense alignment of light waves in a particular direction, an effect known as bi-refringence.
Marcus Loweran astrophysicist at Swinburne University in Australia and co-author of the study, said: «Detecting the bi-refringence of the vacuum requires a magnetic field more than one hundred million times stronger than any ever created on Earth; fortunately nature has provided us with magnetars, which are the perfect cosmic laboratories to search for this effect.” Another co-author of the study, Michela Negroan astrophysicist at Louisiana State University, says: «We are no longer just studying astronomical objects; we are using them to test the laws of nature.”
The Ixpe telescope pushes the limits
In 2017, researchers using the Very Large Telescope in Chile observed hints of polarization of light around a faint neutron star called RX J1856.5-3754, located about 400 light-years from Earth. However, these optical measurements remained open to interpretation, in part due to difficulties in isolating the optical signal.
The scientists noted that a definitive test would require space-based X-ray observatories, particularly NASA’s Imaging X-ray Polarimetry Explorer (Ixpe), which was then still in development. Launching later in 2021, Ixpe carries three identical telescopes designed to measure the polarization of high-energy X-rays.
Star 1E demonstrates bi-refringence
Between March and April 2025 the researchers therefore pointed Ixpe towards 1E 1547-5408, a magnetar that rotates on itself every two seconds and which stands out from the others for its constant emission of radio waves, comparing these data with observations coming from an X-ray telescope on board the International Space Station, as well as from the Australian radio telescope in Murriyang and the South African Radio Astronomy Observatory.
It turned out that the X-rays picked up by Ixpe were almost three times more polarized than those emitted by similar sources, a value far greater than standard models of a neutron star’s surface emission could explain on their own. Second, the polarization was oriented in the same direction as the star’s magnetic field, matching the pattern already observed in its radio waves. Thus the researchers concluded that this combination had the bi-refringence of the vacuum as the only plausible explanation.
New missions will confirm the data
According to Dr Fernando Camilohead of the South African Radio Astronomy Observatory and co-author of the article published in Nature, the discovery represents the culmination of a long journey. Camilo he has been studying the phenomenon since 2007, when he first detected its radio waves using the Murriyang Space Telescope, revealing its two-second rotation speed.
“At the time, 1E-1547 was only the second magnetar in the Milky Way known to emit radio waves, and we were confident that regular monitoring would reveal interesting behavior,” he explains Camilo in the official statement of the discovery, «however, we could never have imagined that twenty years later we would have contributed to investigating a fundamental, and particularly singular, prediction of quantum mechanics».
The team hopes to confirm the discovery with data from future missions, including one called Gosox (Globe Orbiting Soft X-ray Polarimeter), along with more accurate computer simulations to distinguish the vacuum bi-refringence signal from other processes occurring around magnetars.
