This illustration of material swirling around a black hole highlights a special feature, called a “corona,” that glows brightly under x-ray light. In this depiction, the corona can be seen as a purple mist floating in the -above the underlying accretion disk and extending slightly inward from its inner edge. The material inside the internal accretion disk is incredibly hot and would glow with a blinding blue-white light, but here its brightness has been reduced to bring out the corona with better contrast. Its purple color is purely illustrative, replacing the x-ray glow that would not be evident in visible light. The disk warp is a realistic depiction of how the black hole’s immense gravity acts like an optical lens, distorting our view of the flat disk surrounding it. Credit: NASA/Caltech-IPAC/Robert Hurt
New discoveries using data from NASA’s Imaging X-ray Polarimetry Explorer (IXPE) mission offer unprecedented insight into the shape and nature of an important structure for black holes called a corona. The results are published in The Astrophysics Journal.
A corona is a region of moving plasma that is part of the flow of matter toward a black hole, of which scientists have only a theoretical understanding. The new results reveal the shape of the corona for the first time and could help scientists understand the role of the corona in fueling and maintaining black holes.
Many black holes, so named because even light cannot escape their titanic gravity, are surrounded by accretion disks, swirls of gas cluttered with debris. Some black holes also have relativistic jets, which are ultra-powerful explosions of matter thrown into space at high speed by black holes that actively eat matter from their surroundings.
What is perhaps less known is that munching black holes, much like Earth’s sun and other stars, also have a superheated corona. While the solar corona, which is the star’s outermost atmosphere, burns at about 1.8 million degrees Fahrenheit, the temperature of a black hole’s corona is estimated to be billions of degrees.
Astrophysicists had already identified coronas among stellar-mass black holes (those formed by the collapse of a star) and supermassive black holes like the one at the heart of the Milky Way.
“Scientists have long speculated about the composition and geometry of the corona,” said Lynne Saade, a postdoctoral researcher at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and lead author of the new findings. “Is it a sphere above and below the black hole, or an atmosphere generated by the accretion disk, or perhaps plasma located at the base of the jets?”
Enter IXPE, which specializes in x-ray polarization, the characteristic of light that helps map the shape and structure of the most powerful energy sources, illuminating their inner workings even when objects are too small, too bright, or too far away to be seen directly. Just as we can safely observe the solar corona during a total solar eclipse, IXPE provides the means to clearly study the black hole’s accretion geometry, or the shape and structure of its accretion disk and associated structures, including the crown.
“X-ray polarization offers a new way to examine the geometry of black hole accretion,” Saade said. “If the accretion geometry of black holes is similar regardless of their mass, we expect the same to be true for their polarization properties.”
IXPE demonstrated that, among all black holes for which coronal properties could be directly measured by polarization, the corona extended in the same direction as the accretion disk, providing, for the first time, clues to the shape of the crown and clear evidence. of its relationship with the accretion disk. The results rule out the possibility that the crown is shaped like a lamp post hovering above the disk.
The research team studied data from IXPE observations of 12 black holes, including Cygnus X-1 and Cygnus light from Earth, and LMC X-1 and LMC X-3, stellar-mass black holes in the Large Magellanic Cloud more than 165,000 light years away.
IXPE has also observed a number of supermassive black holes, including the one at the center of the Circinus galaxy, 13 million light-years from Earth, and those in the galaxies NGC 1068 and NGC 4151, 47 million years away. -light and nearly 62 million light years away. -years, respectively.
Stellar-mass black holes typically have a mass about 10 to 30 times that of Earth’s sun, while supermassive black holes can have a mass that is millions to tens of billions of times larger. Despite these large differences in scale, the IXPE data suggests that both types of black holes create accretion disks of similar geometry.
That’s surprising, said Marshall astrophysicist and IXPE mission principal investigator Philip Kaaret, because the way the two types are fed is completely different.
“Stellar-mass black holes rip mass from their companion stars, while supermassive black holes devour everything around them,” he said. “Yet the accretion mechanism works in much the same way.”
It’s an exciting prospect, Saade said, because it suggests that studies of stellar-mass black holes, typically much closer to Earth than their much more massive cousins, can also help shed new light on the properties of supermassive black holes.
The team then hopes to carry out additional examinations of both types.
Saade believes there is much more to learn from X-ray studies of these behemoths.
“IXPE has provided X-ray astronomy with the first opportunity in a long time to reveal the underlying processes of accretion and unlock new discoveries about black holes,” she said.
More information:
M. Lynne Saade et al, A comparison of X-ray polarimetric properties of stellar and supermassive black holes, The Astrophysics Journal (2024). DOI: 10.3847/1538-4357/ad73a3
Quote: Imaging X-ray Polarimetry Explorer helps researchers determine the shape of a black hole’s corona (October 17, 2024) retrieved October 17, 2024 from
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