5 ms·

Related video, made by Veritasium yesterday, is one of my favorite videos in a long time. He explained how the prediction of this image was made (before the ima

Related video, made by Veritasium yesterday, is one of my favorite videos in a long time. He explained how the prediction of this image was made (before the image got released) and the video is great and fun to watch. https://www.youtube.com/watch?v=zUyH3XhpLTo https://www.youtube.com/watch?v=zUyH3XhpLTo

ragebol 7y ago
Note that the prediction of the light being brighter on one side did come out.
- jessriedel 7y ago
  What are you basing that on? (Edit:) From one of the papers released today: > The ring is brighter in the south than the north. This can be explained by a combination of motion in the source and Doppler beaming. As a simple example we consider a luminous, optically thin ring... Then the approaching side of the ring is Doppler boosted, and the receding side is Doppler dimmed...This sense of rotation is consistent with the sense of rotation in ionized gas at arcsecond scales ..Notice that the asymmetry of the ring is consistent with the asymmetry inferred from 43 GHz observations of the brightness ratio between the north and south sides of the jet and counter-jet https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 (Edit 2:) Ahh, I see your comment now says "did come out". I initially read it as "did not come out", which was either a misreading on my part (likely) or an earlier edit by you.
  - typon 7y ago
    It's confirmed in the press conference by the scientists. They said its the Doppler beam effect
    - deleted 7y ago
      [deleted]
  - pcmaffey 7y ago
    Are north and south in astronomy defined relative to Earth’s poles? What about “lateral” directions, since east and west are relative (no poles, ie. no east of earth)?
    - jessriedel 7y ago
      I don't know for sure how that's defined (I ctrl-f'd and it's not explained in the paper), but this says the "North" is to the right of the image, and from context it sounds like it's the north pole of the accretion disk, i.e., the direction of the rotation axis with the right-hand rule. > The approaching side of the large-scale jet in M87 is oriented west–northwest (position angle $\mathrm{PA}\approx 288^\circ ;$ in Paper VI this is called ${\mathrm{PA}}_{\mathrm{FJ}}$), or to the right and slightly up in the image.
      - thro_away_n 7y ago
        In paper I, Figure 3, it says North is to the top of the image and East is to the left.
        jessriedel 7y ago
        Whoop. You're right. I misread again.
    - pi-squared 7y ago
      Using the right-hand rule: knowing the direction of spinning, if you point your thumb up and wrap the other four fingers in the direction of rotation, the thumb will be pointing North. Oposite of that is South. East can then be defined along the direction of spinning (eastward or counterclockwise looked from North, the way Earth is spinning) and West - opposite to that, clockwise looked from North, opposite the direction of rotation.

ragebol 7y ago

Note that the prediction of the light being brighter on one side did come out.

jessriedel 7y ago
What are you basing that on? (Edit:) From one of the papers released today: > The ring is brighter in the south than the north. This can be explained by a combination of motion in the source and Doppler beaming. As a simple example we consider a luminous, optically thin ring... Then the approaching side of the ring is Doppler boosted, and the receding side is Doppler dimmed...This sense of rotation is consistent with the sense of rotation in ionized gas at arcsecond scales ..Notice that the asymmetry of the ring is consistent with the asymmetry inferred from 43 GHz observations of the brightness ratio between the north and south sides of the jet and counter-jet https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43 (Edit 2:) Ahh, I see your comment now says "did come out". I initially read it as "did not come out", which was either a misreading on my part (likely) or an earlier edit by you.
- typon 7y ago
  It's confirmed in the press conference by the scientists. They said its the Doppler beam effect
  - deleted 7y ago
    [deleted]
- pcmaffey 7y ago
  Are north and south in astronomy defined relative to Earth’s poles? What about “lateral” directions, since east and west are relative (no poles, ie. no east of earth)?
  - jessriedel 7y ago
    I don't know for sure how that's defined (I ctrl-f'd and it's not explained in the paper), but this says the "North" is to the right of the image, and from context it sounds like it's the north pole of the accretion disk, i.e., the direction of the rotation axis with the right-hand rule. > The approaching side of the large-scale jet in M87 is oriented west–northwest (position angle $\mathrm{PA}\approx 288^\circ ;$ in Paper VI this is called ${\mathrm{PA}}_{\mathrm{FJ}}$), or to the right and slightly up in the image.
    - thro_away_n 7y ago
      In paper I, Figure 3, it says North is to the top of the image and East is to the left.
      - jessriedel 7y ago
        Whoop. You're right. I misread again.
  - pi-squared 7y ago
    Using the right-hand rule: knowing the direction of spinning, if you point your thumb up and wrap the other four fingers in the direction of rotation, the thumb will be pointing North. Oposite of that is South. East can then be defined along the direction of spinning (eastward or counterclockwise looked from North, the way Earth is spinning) and West - opposite to that, clockwise looked from North, opposite the direction of rotation.