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Green Baron

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Everything posted by Green Baron

  1. Guys, you are comparing an artist's impression with real world images. I hoped i could keep this sciency, but sadly this is impossible. You have made it, i am out. Byebye.
  2. The first image is from a cinematic movie, and it is far from reality. The second one is from real life. And it shows the area in the radio spectrum, immediately above the event horizon of a rotating Kerr black hole with an accretion disk just as it was postulated by theory. This is outstanding. For the first time we have a real world image from something that just a few decades ago few people assumed to even exist. There are numerous images and examples of what the direct environment of the event horizon should look like, depending on the orientation, if it is rotating or not, has a
  3. If i understand it right (and i don't pretend to do so), they took several explanations for the jet and the disc into account, and compared them with a set (the "library") of several thousand simulations. Whether all the explanations are relativistic realistic, i cannot tell (former archaeologist, eh), but anyway they did, and out came the one that explains jet, disc and angular momenta best. *drumroll* and it was the one GR predicted for a Kerr black hole. There is no job offer for a pöt on the EHT home page ... i would certainly send in my application :-)
  4. Yes, the black hole's rotation and spacetime distortion plays the bigger part. But, in this case, both, the disc and the hole co-rotate. Didn't want to overcomplicate above ... Edit: and, overall, from paper number I's abstract: "The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole." "Relativistic beaming" being the signal amplification for the approaching part as well as the dampening for the retreating part. So, the Doppler argument is untouched.
  5. It The event horizon is inside the dark area, having a little less than half its diameter. It itself is invisible. There is no ring because this is not an optical image. Measured were the radio waves from the disc alone, in a very narrow band around ~1.3mm lambda and such a subtle structure is below the resolution power of the Interferometer. Resolution power is demonstrated in some of the images with a small white circle. They will try in the future to observe at shorter wavelengths, but for this the dishes must be extremely smooth in order not to introduce errors from unevenness. S
  6. Ok, to make that clear. When looking from above on an object that is turning clockwise, its rotational axis vector (here the z-axis) points away from the observer. That is a left handed coordinate system for the ones like me who fight with 3D stuff and the like (and are about to loose). M87's black hole rotational axis points away from us, in reference to the image we all stare at since yesterday, to the lower left, by 17° from the observational eyesight (the camera's front vector). So, seeing positive z as the normal of the rotational plane that is spanned up by the accretion disc, it's
  7. The 17° is mentioned in paper number V. I put it in a spoiler in a post of mine on the previous page. It was first derived from the jet by VLBI in 2018. It is not an invention of mine ;-) A direct link to the cited work: https://iopscience.iop.org/article/10.3847/1538-4357/aaafcc/meta The paper mentions as well a "counterjet", which is shown in many images, but not as clearly accentuated as the one pointing towards us.
  8. Hey, what's that left-handed guy doing there in the background ? Anyway:
  9. At these speeds, combining pure euclidian geometry and spacetime effects, even a slight angle causes magnitudes of difference in signal strength. The whole thing is actually rotating almost face-on, with a deviation of 17°. There is an image showing the orientation of the arm of the jet aiming towards us. The opposite is invisible. (turn it to the left ~90° to align with the EHT image) The bright point is the galaxy M87. Space is mindbogglingly huge.
  10. There are two different things here: The magnetic field lines do not directly create the image. Magnetic fields develop in the accretion disc of plasma (charged particles) from differential rotation speed being faster on the inner and slower on the outer part. They are twisted by the rotating black hole (through mechanisms i don't completely understand without diving deeper into it) in a form that they accelerate material from the disc towards the poles and from there out into space. The orientation of this jet, assuming that it is rectangular to the disc, enables them to calculate the di
  11. Sorry for my being unclear. I was not referring to the authors of the EHT collaboration and the papers they produced, that is outstanding work. It was @p1t1o's remark about second hand sources, that on every site he read the description/explanation of what was presented was slightly different. With that, so i assumed, he meant pop science articles and social media sites commenting on the news. And, i may say, i have some experience with journalists :-) They can't know everything about everything, just like us, they read and try to understand, and sometimes they are good, sometimes we are bette
  12. Yeah, well, it was written with some humour :-) If people like Ainsteene more, i know who's meant. To be clear: the ring does not show optical data from an imaging optical telescope, it is processed data from overlaid radio signals, obtained by receivers all around the world. What is so outstanding is the resolution. Where the ring is brighter, the radio signals have been stronger. The edge of the dark centre is where photons are going around the event horizon very closely (like 2 Schwarzschild radii). The black hole itself is rotating very fast, and together with the doppler effect
  13. Edit: I would interpret this as an evidence that the authors of these articles aren't cleverer than ourselves Overview on the EHT homepage: https://eventhorizontelescope.org/ and special issue of the ApJ Letters, with summary: https://iopscience.iop.org/journal/2041-8205/page/Focus_on_EHT Scroll down for the links to the detail papers, which are pretty comprehensible. -------------- I read that the 2018 observation campaign fell victim to adverse weather conditions, 2019 had technical problems. Hopes are on next year's campaign with added telescopes an
  14. [unimportant remark about Schwarzschild deleted]
  15. Sgr A* changes quickly, even during one session, while M87 stays still. That complicates data evaluation. "very soon" they say very TM :-)
  16. Our central black hole has a slightly greater angular size than the M87 one, as observed from earth, but it is behind thick interstellar clouds. The dark depression in the image presented is about double the size of the actual event horizon that would fit the mass 6.5 billion solar masses.
  17. They mention somewhere that an image of SgrA* drawn out of data from the 2017 campaign can be expected. If i understood it right, some adjustments must be made to the data crunching, so it may take some more time (interpretation mine). Also, only a part of the petabytes of data has been used for the analyses presented today. When the French NOEMA and the Greenland Telescope will join (this and the next year), there will be another leap in sensitivity, which may enable them to actually do "movies" of the swirling disc. Within the limits of the uncertainties (that may be pushed fu
  18. A sixth paper that is not in the "special edition" of ApJ letters above: https://iopscience.iop.org/article/10.3847/2041-8213/ab1141 They are all openly licensed and surprisingly understandable.
  19. Here's food: https://iopscience.iop.org/journal/2041-8205 Looks like being open access. Have fun :-) (retreats in a cave for reading)
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