Credit: NASA/Caltech-IPAC/Robert Hurt
Sculpting a Black Hole's Corona
Polarization is a directional property of scattered light. Sunlight scattered from a metallic surface is mostly oriented perpendicular to the surface, so polarized sunglasses work by filtering out most of the light oriented in this direction. Polarized light can be used to navigate from place to place, or even to find a mate. NASA's Imaging X-ray Polarimeter Explorer, or IXPE, is a unique X-ray space telescope sensitive to the polarization of X-ray radiation from strange sources like black holes and neutron stars. Measurement of X-ray polarization from accreting black holes by IXPE can provide information on the shape of the material feeding the black hole, information that's impossible to directly obtain in other ways. Material falling into a black hole doesn't fall directly into the black hole from all directions, but rather forms a thin spiralling disk around the black hole before plunging through the black hole's event horizon beyond the inner edge of the disk. Surrounding the disk is a superhot region of ionized gas which scientists call the corona. The corona is believed to be produced by the twisting of magnetic fields in the inner part of the accretion disk, and, at temperatures of billions of degrees, is one of the most extreme environments in the Universe. Little is known about the shape of the corona, since (unlike the Sun's corona) it cannot be directly imaged. Simple models of the geometry of the corona have been posed, but none are entirely successful. Now, for the first time, scientists have used the polarization signature of X-rays from the corona to help constrain the corona's shape. A recent study of accreting black holes by IXPE, covering black hole mass ranges from a few times the mass of the Sun to many millions of times the Sun's mass, showed that the polarization of X-rays from the corona is similar to the polarization of light from the accretion disk itself.
The image above is an artist's illustration of a black hole's accretion disk. Radiation from matter in the accretion disk behind the black hole travels along the warped spacetime near the black hole producing an apparent distortion in the shape of the accretion disk. The X-ray emitting corona is shown as a purple haze above the disk. The IXPE measurements rule out at least one popular model for the shape of the corona, at least for the black holes that were observed by IXPE, and furthermore directly tie the shape of the corona to the accretion disk itself.
Published: November 18, 2024
<
HEA Dictionary ● Archive
● Search HEAPOW
● Other Languages
● HEAPOW on Facebook
● Download all Images
● Education ● HEAD
>
Each week the HEASARC
brings you new, exciting and beautiful images from X-ray and Gamma ray
astronomy. Check back each week and be sure to check out the HEAPOW archive!
Page Author: Dr. Michael F. Corcoran
Last modified Monday, 18-Nov-2024 11:38:47 EST