2 ms·

"[EHT Sagittarius A* (Sgr A*)] Milky Way black hole has 'strong, twisted' magnetic field in mesmerizing new [polarized (phase filtered)] image" (2024-03) https

• westurner 2y ago
  "First image of our Milky Way's black hole [Sagittarius A*] may be inaccurate, scientists say" (2024-10) https://news.ycombinator.com/item?id=42087932 https://news.ycombinator.com/item?id=42087932 https://www.space.com/the-universe/black-holes/1st-image-of-our-milky-ways-black-hole-may-be-inaccurate-scientists-say https://www.space.com/the-universe/black-holes/1st-image-of-... : > "We hypothesize that the ring image resulted from errors during EHT's imaging analysis and that part of it was an artifact, rather than the actual astronomical structure." > The ring-like structure, which really represents intense radio waves blasted from the brilliant disk of gas, known as the "accretion disk," that's swirling around the black hole, may in fact be more elongated than appears, the researchers argue "An Independent Hybrid Imaging of Sgr A* from the Data in EHT 2017 Observations" (2024-10) https://doi.org/10.1093/mnras/stae1158 https://doi.org/10.1093/mnras/stae1158 https://academic.oup.com/mnras/article/534/4/3237/7660988 https://academic.oup.com/mnras/article/534/4/3237/7660988 : > To mitigate the time variability in the Sgr A* structure, data weighting strategies derived from general relativistic magnetohydrodynamical (GRMHD) simulations with the source-size assumption are used. In addition, the EHTC analysis uses a unique criterion for selecting the final image. It is not based on consistency with the observed data, but rather on the highest rate of appearance of the image morphology from a wide imaging parameter space. Our concern is that these methods may interfere with the PSF deconvolution and cause the resulting image to reflect more structural features of the PSF than of the actual intrinsic source. > On the other hand, our independent analysis used traditional very long baseline interferometry (VLBI) imaging techniques to derive our final image. We used the hybrid mapping method, which is widely accepted as the standard approach, namely iterations between imaging by the clean algorithm and calibrating the data by self-calibration, following well-established precautions. In addition, we performed a comparison with the PSF structure, noting the absence of distinct PSF features in the resulting images. Finally, we selected the image with the highest degree of consistency with the observational data." > Our final image shows that the eastern half of this structure is brighter, which may be due to a Doppler boost from the rapid rotation of the accretion disc. We hypothesize that our image indicates that a portion of the accretion disc, located approximately 2 to several R_S (where R_S is the Schwarzschild radius) away from the black hole, is rotating at nearly 60% of the speed of light and is seen at an angle of 40°−45° (Section 4).
  • westurner 2y ago
    > general relativistic magnetohydrodynamical (GRMHD) Magnetohydrodynamics; fluids and electricity: https://en.wikipedia.org/wiki/Magnetohydrodynamics https://en.wikipedia.org/wiki/Magnetohydrodynamics Magnetorotational instability: https://en.wikipedia.org/wiki/Magnetorotational_instability https://en.wikipedia.org/wiki/Magnetorotational_instability SPH: 1970s QHD: Quantum Hydrodynamics SQS: Superfluid Quantum Space SQG: Superfluid Quantum Gravity and SQR: Superfluid Quantum Relativity Fedi's > Schwarzschild radius Does this image help to confirm or reject the Shwarzschild radius, or whether black holes have hair or turbulence at the boundary we've been calling the event horizon though Hawking radiation permeates through all such boundaries in at least some directions? > which may be due to a Doppler boost from the rapid rotation of the accretion disc. How much does the thermal energy vary within the (already physically distributed) matter surrounding the black hole? Isn't there reason to believe that things are in a different phase of matter at those darker temperatures ? Are there superfluid states at those thermal ranges? Are our phase transition diagrams complete? Standard phase transition diagrams do not describe the Mpemba effect, for example. TODOcite. Does fusion plasma research have insight into the phases of matter at higher temperatures? What are the temperatures around the disturbance? Does M87a show a similar Doppler effect as this analysis suggests affects the 2017 EHT Sgr A* image?
    • westurner 2y ago
      > Mpemba effect, phase transitions And whether that matters for imaging of an accretion disc > From "Exploring Quantum Mpemba Effects" (2024) https://physics.aps.org/articles/v17/10 https://physics.aps.org/articles/v17/10 : > Similar processes, in which a system relaxes to equilibrium more quickly if it is initially further away from equilibrium, are being intensely explored in the microscopic world. Now three research teams provide distinct perspectives on quantum versions of Mpemba-like effects, emphasizing the impact of strong interparticle correlations, minuscule quantum fluctuations, and initial conditions on these relaxation processes [3–5]. The teams’ findings advance quantum thermodynamics Is quantum thermodynamics modeled in the (GRMHD) magnetohydrodynamics applied? From https://news.ycombinator.com/item?id=42369294#42371946 https://news.ycombinator.com/item?id=42369294#42371946 https://westurner.github.io/hnlog/#comment-42371946 https://westurner.github.io/hnlog/#comment-42371946 : > Dark fluid: https://en.wikipedia.org/wiki/Dark_fluid https://en.wikipedia.org/wiki/Dark_fluid : >> Dark fluid goes beyond dark matter and dark energy in that it predicts a continuous range of attractive and repulsive qualities under various matter density cases. Indeed, special cases of various other gravitational theories are reproduced by dark fluid, e.g. inflation, quintessence, k-essence, f(R), Generalized Einstein-Aether f(K), MOND, TeVeS, BSTV, etc. Dark fluid theory also suggests new models, such as a certain f(K+R) model that suggests interesting corrections to MOND that depend on redshift and density