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Imaging X-ray Polarimetery Explorer (IXPE) Conference Presentation at the 244th Meeting of the American Astronomical Society
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Written by Michael Allen
An international team of astronomers using NASA’s IXPE (Imaging X-ray Polarimetry Explorer), has challenged our understanding of what happens to matter in the direct vicinity of a black hole.
With IXPE, astronomers can study incoming X-rays and measure the polarization, a property of light that describes the direction of its electric field.
The polarization degree is a measurement of how aligned those vibrations are to each other. Scientists can use a black hole’s polarization degree to determine the location of the corona – a region of extremely hot, magnetized plasma that surrounds a black hole – and how it generates X-rays.
This illustration of material swirling around a black hole highlights a particular feature, called the “corona,” that shines brightly in X-ray light. In this depiction, the corona can be seen as a purple haze floating above the underlying accretion disk, and extending slightly inside of its inner edge. The material within the inner accretion disk is incredibly hot and would glow with a blinding blue-white light, but here has been reduced in brightness to make the corona stand out with better contrast. Its purple color is purely illustrative, standing in for the X-ray glow that would not be obvious in visible light. The warp in the disk is a realistic representation of how the black hole’s immense gravity acts like an optical lens, distorting our view of the flat disk that encircles it. NASA/Caltech-IPAC/Robert Hurt In April, astronomers used IXPE to measure a 9.1% polarization degree for black hole IGR J17091-3624, much higher than they expected based on theoretical models.
“The black hole IGR J17091-3624 is an extraordinary source which dims and brightens with the likeness of a heartbeat, and NASA’s IXPE allowed us to measure this unique source in a brand-new way.” said Melissa Ewing, the lead of the study based at Newcastle University in Newcastle upon Tyne, England.
In X-ray binary systems, an extremely dense object, like a black hole, pulls matter from a nearby source, most often a neighboring star. This matter can begin to swirl around, flattening into a rotating structure known as an accretion disc.
The corona, which lies in the inner region of this accretion disc, can reach extreme temperatures up to 1.8 billion degrees Fahrenheit and radiate very luminous X-rays. These ultra-hot coronas are responsible for some of the brightest X-ray sources in the sky.
Despite how bright the corona is in IGRJ17091-364, at some 28,000 light-years from Earth, it remains far too small and distant for astronomers to capture an image of it.
“Typically, a high polarization degree corresponds with a very edge-on view of the corona. The corona would have to be perfectly shaped and viewed at just the right angle to achieve such a measurement,” said Giorgio Matt, professor at the University of Roma Tre in Italy and a co-author on this paper. “The dimming pattern has yet to be explained by scientists and could hold the keys to understanding this category of black holes.”
The stellar companion of this black hole isn’t bright enough for astronomers to directly estimate the system’s viewing angle, but the unusual changes in brightness observed by IXPE suggest that the edge of the accretion disk was directly facing Earth.
The researchers explored different avenues to explain the high polarization degree.
In one model, astronomers included a “wind” of matter lifted from the accretion disc and launched away from the system, a rarely seen phenomenon. If X-rays from the corona were to meet this matter on their way to IXPE, Compton scattering would occur, leading to these measurements.
Fast Facts
Polarization measurements from IXPE carry information about the orientation and alignment of emitted X-ray light waves. The high the degree of polarization, the more the X-ray waves are traveling in sync. Most polarization in the corona come from a process known as Compton scattering, where light from the accretion disc bounces off the hot plasma of the corona, gaining energy and aligning to vibrate in the same direction. “These winds are one of the most critical missing pieces to understand the growth of all types of black holes,” said Maxime Parra, who led the observation and works on this topic at Ehime University in Matsuyama, Japan. “Astronomers could expect future observations to yield even more surprising polarization degree measurements.”
Another model assumed the plasma in the corona could exhibit a very fast outflow. If the plasma were to be streaming outwards at speeds as high as 20% the speed of light, or roughly 124 million miles per hour, relativistic effects could boost the observed polarization.
In both cases, the simulations could recreate the observed polarization without a very specific edge-on view. Researchers will continue to model and test their predictions to better understand the high polarization degree for future research efforts.
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.
Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
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Last Updated Aug 12, 2025 EditorBeth RidgewayContactCorinne Edmistoncorinne.m.edmiston@nasa.govLocationMarshall Space Flight Center Related Terms
IXPE (Imaging X-ray Polarimetry Explorer) Marshall Astrophysics Marshall Science Research & Projects Marshall Space Flight Center Explore More
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
An international team of astronomers has uncovered new evidence to explain how pulsing remnants of exploded stars interact with surrounding matter deep in the cosmos, using observations from NASA’s IXPE (Imaging X-ray Polarimetry Explorer) and other telescopes.
Scientists based in the U.S., Italy, and Spain, set their sights on a mysterious cosmic duo called PSR J1023+0038, or J1023 for short. The J1023 system is comprised of a rapidly rotating neutron star feeding off of its low-mass companion star, which has created an accretion disk around the neutron star. This neutron star is also a pulsar, emitting powerful twin beams of light from its opposing magnetic poles as it rotates, spinning like a lighthouse beacon.
The J1023 system is rare and valuable to study because the pulsar transitions clearly between its active state, in which it feeds off its companion star, and a more dormant state, when it emits detectable pulsations as radio waves. This makes it a “transitional millisecond pulsar.”
An artist’s illustration depicting the central regions of the binary system PSR J1023+0038, including the pulsar, the inner accretion disc and the pulsar wind. Credit: Marco Maria Messa, University of Milan/INAF-OAB; Maria Cristina Baglio, INAF-OAB “Transitional millisecond pulsars are cosmic laboratories, helping us understand how neutron stars evolve in binary systems,” said researcher Maria Cristina Baglio of the Italian National Institute of Astrophysics (INAF) Brera Observatory in Merate, Italy, and lead author of a paper in The Astrophysical Journal Letters illustrating the new findings.
The big question for scientists about this pulsar system was: Where do the X-rays originate? The answer would inform broader theories about particle acceleration, accretion physics, and the environments surrounding neutron stars across the universe.
The source surprised them: The X-rays came from the pulsar wind, a chaotic stew of gases, shock waves, magnetic fields, and particles accelerated near the speed of light, that hits the accretion disk.
To determine this, astronomers needed to measure the angle of polarization in both X-ray and optical light. Polarization is a measure of how organized light waves are. They looked at X-ray polarization with IXPE, the only telescope capable of making this measurement in space, and comparing it with optical polarization from the European Southern Observatory’s Very Large Telescope in Chile. IXPE launched in Dec. 2021 and has made many observations of pulsars, but J1023 was the first system of its kind that it explored.
NASA’s NICER (Neutron star Interior Composition Explorer) and Neil Gehrels Swift Observatory provided valuable observations of the system in high-energy light. Other telescopes contributing data included the Karl G. Jansky Very Large Array in Magdalena, New Mexico.
The result: scientists found the same angle of polarization across the different wavelengths.
“That finding is compelling evidence that a single, coherent physical mechanism underpins the light we observe,” said Francesco Coti Zelati of the Institute of Space Sciences in Barcelona, Spain, co-lead author of the findings.
This interpretation challenges the conventional wisdom about neutron star emissions of radiation in binary systems, the researchers said. Previous models had indicated that the X-rays come from the accretion disk, but this new study shows they originate with the pulsar wind.
“IXPE has observed many isolated pulsars and found that the pulsar wind powers the X-rays,” said NASA Marshall astrophysicist Philip Kaaret, principal investigator for IXPE at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “These new observations show that the pulsar wind powers most of the energy output of the system.”
Astronomers continue to study transitional millisecond pulsars, assessing how observed physical mechanisms compare with those of other pulsars and pulsar wind nebulae. Insights from these observations could help refine theoretical models describing how pulsar winds generate radiation – and bring researchers one step closer, Baglio and Coti Zelati agreed, to fully understanding the physical mechanisms at work in these extraordinary cosmic systems.
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
Share
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Last Updated Jul 15, 2025 EditorBeth RidgewayContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
IXPE (Imaging X-ray Polarimetry Explorer) Marshall Astrophysics Marshall Science Research & Projects Marshall Space Flight Center Explore More
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