{"id":576571,"date":"2026-08-22T05:12:24","date_gmt":"2026-08-22T05:12:24","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/576571\/"},"modified":"2026-08-22T05:12:24","modified_gmt":"2026-08-22T05:12:24","slug":"extreme-x-rays-from-a-magnetar-exposes-that-empty-space-may-not-be-empty","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/576571\/","title":{"rendered":"Extreme X-rays from a magnetar exposes that empty space may not be empty"},"content":{"rendered":"

A highly magnetized neutron star produced unusually polarized X-rays, offering some of the strongest evidence yet that empty space can change how light travels.The star\u2019s extreme magnetic field may be affecting short-lived particle pairs in the quantum vacuum, keeping the X-rays strongly aligned with the magnetic field<\/a>.The signal is not yet a definitive detection. More X-ray observations and improved simulations will be needed to confirm whether vacuum birefringence is responsible.<\/p>\n

A magnetar with a magnetic field trillions of times stronger than Earth\u2019s has produced an unusually polarized X-ray signal, giving astronomers some of their strongest evidence yet that empty space can alter how light travels.<\/p>\n

The effect, called vacuum birefringence, comes from quantum electrodynamics, or QED. The theory predicts that a vacuum is not truly empty. Virtual electron-positron pairs can briefly appear, and an intense magnetic field can affect how different orientations of light move through that quantum vacuum<\/a>.<\/p>\n

The new observations focus on 1E 1547.0\u22125408, a magnetar with a 2.09-second spin period and a surface equatorial magnetic field of about 2.2 \u00d7 10^14 gauss. The work combined X-ray measurements from NASA\u2019s Imaging X-ray Polarimetry Explorer, or IXPE, with NICER observations and radio data from Murriyang, CSIRO\u2019s Parkes radio telescope.<\/p>\n

X-rays arrive with unusually strong polarization<\/p>\n

IXPE measured an average X-ray polarization degree of about 46% across the 2 to 8 kiloelectronvolt energy range. In the softest 2 to 3 keV band, that figure reached 59 \u00b1 5%.<\/p>\n

Energy-resolved IXPE polarization measurements. Background-subtracted and phase-averaged polarization measurements of 1E 1547.0\u22125408. (CREDIT: Marcus Lower et al, Nature) <\/p>\n

At certain rotational phases, the polarization became even stronger. In the 2 to 4 keV range, it peaked at 74 \u00b1 11%. In the narrower 2 to 3 keV band, it reached 82 \u00b1 15%.<\/p>\n

Those values stand out among magnetars<\/a> already observed by IXPE. The 2 to 3 keV polarization degree was at least 2.5 times larger than corresponding measurements in the rest of the observed magnetar population.<\/p>\n

The polarization angle also changed in a smooth, roughly sinusoidal pattern as the star rotated. That behavior resembled the pattern seen in radio observations, although the X-ray and radio signals were offset in rotational phase.<\/p>\n

A joint IXPE and NICER analysis also found that the soft X-ray emission was dominated by a thermal component with a temperature of 0.72 \u00b1 0.01 keV. Assuming a distance of 4.5 kiloparsecs, the emitting region had a radius of about 1.07 kilometers, consistent with a relatively small surface hotspot.<\/p>\n

The high polarization is difficult to reproduce with standard surface and atmospheric models alone. A pure magnetized atmosphere<\/a> may produce phase-averaged polarization approaching about 40%, but values near 65% are harder to explain. The phase-resolved levels of roughly 70% to 80% create an even stronger challenge.<\/p>\n

Radio pulses reveal an unusually favorable geometry<\/p>\n

The radio observations provided another important piece of the puzzle. The polarization position angle traced an S-shaped sweep that matched the rotating vector model for a dipolar magnetic field.<\/p>\n

That fit indicates that the magnetar is a nearly aligned rotator. Its magnetic and rotational axes sit close together, while Earth\u2019s line of sight lies near the spin axis.<\/p>\n

Illustration of a rotating NS with a dipole magnetic field geometry described by the RVM. (CREDIT: Marcus Lower et al, Nature) <\/p>\n

This geometry gives astronomers an unusually favorable view of the magnetic field. The broad radio pulse spans about 25% of the star\u2019s rotation, and the inferred radio emission height is less than 1% of the light-cylinder radius.<\/p>\n

\u201cDetecting vacuum birefringence requires a magnetic field that is over 100 million times stronger than any we’ve ever made on Earth. Thankfully, nature has provided us with magnetars, which are the perfect cosmic laboratories to go looking for this effect,\u201d Dr. Lower said.<\/p>\n

The geometry matters because vacuum birefringence should keep the polarization direction of X-rays closely tied to the large-scale magnetic field as the radiation moves outward. In the team\u2019s interpretation, the exceptionally high polarization and relatively modest angle changes fit that expectation.<\/p>\n

\u201cBecause of the magnetic field’s strength, Heisenberg’s virtual particles become aligned with the direction the field is pointing,\u201d Dr. Lower said.<\/p>\n

\u201cBy carefully tracking the direction the radio waves and X-rays<\/a> oscillate as the magnetar rotates, the team found that the alignment of 1E1547’s magnetic and rotational poles were ideal for detecting vacuum birefringence.\u201d<\/p>\n

A polarization drop may point to another QED effect<\/p>\n

The X-ray polarization did not remain constant with energy. It fell from 59 \u00b1 5% in the 2 to 3 keV band to 37 \u00b1 5% between 3 and 4 keV.<\/p>\n

Model-dependent and model-independent polarization characteristics comparison. (CREDIT: Marcus Lower et al, Nature) <\/p>\n

The researchers argue that this decrease is most naturally explained by polarization mode conversion near a QED vacuum resonance. In a magnetized hydrogen atmosphere, vacuum and plasma effects can cause photons to switch between two polarization modes.<\/p>\n

For 1E 1547.0\u22125408, that conversion is expected to become efficient at energies above about 2 keV. The process can reduce the net polarization escaping the surface.<\/p>\n

At higher energies, the interpretation becomes less certain. IXPE measured a 40 \u00b1 11% polarization degree between 4 and 8 keV, but the signal had a lower signal-to-noise ratio and only a 3.5-sigma detection significance.<\/p>\n

The team also modeled the X-ray intensity and polarization with the MAGTHOMSCATT radiative transfer code<\/a>. Configurations that included magnetospheric vacuum birefringence better matched the phase-resolved polarization data than models that neglected the effect.<\/p>\n

Those simulations remain model-dependent. The researchers also note that deeper IXPE observations are needed, especially at higher energies where the current measurements are less precise.<\/p>\n

Practical implications of the research<\/p>\n

Vacuum birefringence has been predicted since the 1930s, but a definitive direct detection has remained out of reach. The new magnetar observations offer a way to test the prediction under magnetic fields far stronger than any produced on Earth.<\/p>\n

If future observations confirm the interpretation, magnetars could become powerful laboratories for studying non-linear QED in extreme conditions. Lower-energy X-ray polarization<\/a> measurements may be especially useful because even higher polarization degrees are expected there.<\/p>\n

X-ray spectro-polarimetric posterior distributions. (CREDIT: Marcus Lower et al, Nature) <\/p>\n

Future IXPE observations, possible soft X-ray polarimetry missions such as GoSOX, and complementary laboratory and collider experiments could make the test more stringent.<\/p>\n

\u201cWith these future data on hand and our updated simulations, we may finally be able to complete the quest started by Heisenberg nearly 90 years ago.\u201d<\/p>\n

Dig deeper into magnetars and polarized X-rays<\/p>\n

These resources explore how extreme magnetic fields affect light, how X-ray polarization reveals magnetar physics, and how astronomers are testing quantum electrodynamics under conditions impossible to reproduce on Earth.<\/p>\n

X-ray Polarization from Magnetar Sources<\/a>
This review summarizes the first years of IXPE magnetar observations and explains how X-ray polarization can probe magnetic-field structure, neutron-star surfaces and possible vacuum-birefringence effects. (Galaxies, 2024)<\/p>\n

X-ray polarization in magnetar atmospheres \u2013 effects of mode conversion<\/a>
The authors model how photons can switch polarization modes near the QED vacuum resonance, demonstrating how this process can reduce polarization and create energy-dependent signatures important for interpreting magnetar observations. (Monthly Notices of the Royal Astronomical Society, 2024)<\/p>\n

Polarized x-rays from a magnetar<\/a>
One of IXPE\u2019s foundational magnetar studies measured polarized X-rays from 4U 0142+61 and showed how polarization can distinguish competing models of a magnetar\u2019s surface, atmosphere and magnetosphere while testing strong-field quantum physics. (Science, 2022)<\/p>\n

Research findings are available online in the journal Nature<\/a>.<\/p>\n

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