IXPE Measures X-Ray Polarization from Magnetic Explosions

A magnetor is a type of neutron star that boasts an extraordinarily strong magnetic field, approximately one times stronger than Earth’s magnetic field. These colossal magnetic fields are believed to be generated when rapidly rotating neutron stars are birthed from the collapse of a giant star’s core. Magnetars emit brilliant X-rays and display erratic patterns of activity, with bursts and flares releasing millions of times more energy than the Sun emits in just one second. Polarization measurements offer insights into magnetic fields and surface characteristics. This was the focus of astronomers using the NASA Imaging X-ray Polarization Explorer (IXPE) to study 1E 1841-045, a magnetor located within Supernova Remnant (SNR) KES 73, situated nearly 28,000 light years from Earth. The findings are published in the Astrophysics Journal Letter.

Magnetors represent a category of young neutron stars. They are the remnants of giant stars that collapsed in on themselves at the end of their life cycles, resembling the mass of the Sun but compressed into a city-sized volume.

Neutron stars exemplify some of the most extreme physical conditions in the observable universe, offering a unique chance to investigate states that cannot be replicated in terrestrial laboratories.

The 1E 1841-045 magnetor was observed in an explosive state on August 21, 2024, by NASA’s Swift, Fermi, and other advanced telescopes.

The IXPE team has permitted several requests to pause scheduled observations of the telescope multiple times each year, redirecting focus to unique and unexpected celestial phenomena.

When 1E 1841-045 transitioned into this bright active phase, scientists chose to direct IXPE to capture the first polarization measurements of the magnetor’s flare.

Magnetors possess magnetic fields thousands of times stronger than most neutron stars, hosting the most powerful magnetic fields among known cosmic entities.

These extreme magnetic field fluctuations can lead to the emission of X-ray energies up to 1,000 times greater than usual for several weeks.

This heightened state is referred to as explosive activity, though the underlying mechanisms remain poorly understood.

IXPE’s X-ray polarization measurements may help unveil the mysteries behind these phenomena.

Polarized light carries information about the direction and orientation of emitted X-ray waves. A higher degree of polarization indicates that the X-ray waves are moving in harmony, akin to a tightly choreographed dance.

Studying the polarization characteristics of magnetors provides clues regarding the energy processes associated with observed photons and the direction and configuration of the magnetor’s magnetic field.

This diagram illustrates the IXPE measurements of X-ray polarized light emitted by 1E 1841-045. Image credit: Michela Rigoselli / Italian National Institute of Astrophysics.

IXPE results, supported by NASA’s Nustar and other telescope observations, indicate that X-ray emissions from 1E 1841-045 exhibit increased polarization at higher energy levels while maintaining a consistent emission direction.

This significant contribution to the high degree of polarization is attributed to the hard X-ray tail of 1E 1841-045, a highly energetic component of the magnetosphere responsible for the highest photon energies detected by IXPE.

Hard X-rays refer to X-rays characterized by shorter wavelengths and greater energy than soft X-rays.

While prevalent in magnetars, the processes that facilitate the generation of these high-energy X-ray photons remain largely enigmatic.

Despite several proposed theories explaining this emission, the high polarization associated with these hard X-rays currently offers additional clues to their origins.

“This unique observation enhances existing models that aim to explain magnetic hard X-ray emissions by elucidating the extensive synchronization seen among these hard X-ray photons,” remarked a student from George Washington University. First paper.

“This effectively demonstrates the power of polarization measurements in refining our understanding of the physics within a magnetar’s extreme environment.”

“It would be fascinating to observe 1E 1841-045 as it returns to its stable baseline state and to track the evolution of polarization,” added Dr. Michela Rigoselli, an astronomer at the National Institute of Astrophysics in Italy. Second paper.

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Rachel Stewart et al. 2025. X-ray polarization of Magnetor 1E 1841-045. apjl 985, L35; doi: 10.3847/2041-8213/adbffa

Michela Rigoselli et al. 2025. IXPE detection of highly polarized X-rays from Magnetor 1E 1841-045. apjl 985, L34; doi: 10.3847/2041-8213/adbffb