Imaging a black hole - the EHT

[p1t1o]

I find it hard to imagine the disc ever rotating opposite to the hole, would not frame-dragging quickly reverse this?

 

5 hours ago, Green Baron said:

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. Shorter wavelengths (higher frequency) would mean better resolution with given diameter (resolution ~= lambda/diameter).

Clearly, they should have sent a poet...

 

[Green Baron]

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 :-)

Edited April 12, 2019 by Green Baron

[Cassel]

7 hours ago, Green Baron said:

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. Shorter wavelengths (higher frequency) would mean better resolution with given diameter (resolution ~= lambda/diameter).

Then how do you know that it exists?

This picture had something to prove, and it turns out that it still did not prove anything. You still are talking about assumptions, because many things are invisible.

In this way, physicists believe that a black hole should look like

And telescopes were directed at such a celestial body

Can you see the difference? I see the difference.
Now the question is whether the object is a black hole or something else? Or is this the way the black holes looks in reality, but the hypothesis that say how the black hole is supposed to look are wrong?

Edited April 12, 2019 by Cassel

[kerbiloid]

It now has a name: Powehi.
In translation - "donut"  "bagel" "pumpernickel" "the adorned fathomless dark creation"

https://www.theguardian.com/science/2019/apr/12/powehi-black-hole-gets-a-name-meaning-the-adorned-fathomless-dark-creation

[Green Baron]

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 an accretion disk or not etc. Some are discussed, including alternatives, in the papers.

https://eventhorizontelescope.org/simulations-gallery

Now actually with a little more real world background than before, as the example we have behaves like simulated. I find this really cool.

We can expect more, and possible different looking black holes, with better instruments and techniques. Sgr A* may be the next. The even talk about stellar black holes, but that may still be future music.

I want a radio telescope (and if we're already there an optical one as well) in each earth/moon or earth/sun lagrange point :-)

Edited April 12, 2019 by Green Baron

[kerbiloid]

If this picture is made on the Earth, imagine the images from the 550 AU far heliocentric orbit, once humans make at least a gas-core booster for the telescopes.

[Starstruck69]

16 hours ago, Cassel said:

Then how do you know that it exists?

This picture had something to prove, and it turns out that it still did not prove anything. You still are talking about assumptions, because many things are invisible.

In this way, physicists believe that a black hole should look like

And telescopes were directed at such a celestial body

Can you see the difference? I see the difference.
Now the question is whether the object is a black hole or something else? Or is this the way the black holes looks in reality, but the hypothesis that say how the black hole is supposed to look are wrong?

They look very similar to me, just on different frequences. One is in visible spectrum and the other radio.

[Starstruck69]

If we look at Hawkins equation to find temperature of a black hole i use this one below

Everything in there is a constant apart from M = mass.

So the matter beyond the event horizon is cold. Very cold.

This got me thinking, even if it was hot would we still see it, measure it?? We know that photons (electromagnet particles) cannot escape, so how do we know that the matter is not shrouded due to the gravitational field of the BH. 

I have pondered this one for a couple of days now. Can anybody shed some light on this? No pun intended..

 

 

Edited April 13, 2019 by Starstruck69

[Cassel]

4 minutes ago, Starstruck69 said:

They look very similar to me, just on different frequences. One is in visible spectrum and the other radio.

The first picture shows the event horizon, the second one does not. The first one shows the ring of equal brightness and the other does not.

It's probably the best that captures what I mean.

 

The photons emitted by the ring should orbit the black hole and be visible on both sides equally. In this case, the image of the ring should be equally bright on both sides, and the Doppler effect should not be visible. Ring on both sides of the black hole at the same time should be visible as ring of mixed photons, those from the part of the ring that moves away from us and those from the part of the ring that move towards us?

[Starstruck69]

4 minutes ago, Cassel said:

The first picture shows the event horizon, the second one does not. The first one shows the ring of equal brightness and the other does not.

It's probably the best that captures what I mean.

 

The photons emitted by the ring should orbit the black hole and be visible on both sides equally. In this case, the image of the ring should be equally bright on both sides, and the Doppler effect should not be visible. Ring on both sides of the black hole at the same time should be visible as ring of mixed photons, those from the part of the ring that moves away from us and those from the part of the ring that move towards us?

Interesting, i see your point. Have you ruled out lensing?

[Green Baron]

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.

[Starstruck69]

Am i? I agreed with your point, read back

1 hour ago, Starstruck69 said:

They look very similar to me, just on different frequences. One is in visible spectrum and the other radio.

 

Maybe to be clear what i should have put in there is one is an artist impression to demonstrate in the visible spectrum and the other a real image in the radio...

Bear in mind published books are full of hypothetical artist images of BH. Up untill a few days ago that was all we had.

[Cassel]

1 hour ago, Green Baron said:

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.

It is not real because it was generated by a computer based on algorithm.

Meanwhile, what you call artistic impression is the expectations that physicists had and graphic artist drew it :-)

Edited April 13, 2019 by Cassel

[Cassel]

1 hour ago, Starstruck69 said:

Interesting, i see your point. Have you ruled out lensing?

How would it work in this case?

[Delay]

8 minutes ago, Cassel said:

It is not real because it was generated by a computer based on algorithm.

...Which got the information based on real world observations. The algorithms simply put all the pieces together to form an image.

According to your logic any composite is also not a real image since they're also pieced together by an algorithm. Say goodbye to Curiosity's selfies then, they're not photos apparently!

 

Artist's impressions are just that: artist's impressions.

[Starstruck69]

48 minutes ago, Cassel said:

Meanwhile, what you call artistic impression is the expectations that physicists had and graphic artist drew it :-)

I think i understand your angle here. The point is nothing can be measured or observed from this as it is just a humans visualisation from an artists best guess using physics a basic guide. Still valuable though in my opinion it can help some people visualise a BH. Ultimately it generates no data for us. I get your point though and agree with you on a certain level.

48 minutes ago, Cassel said:

It is not real because it was generated by a computer based on algorithm.

Define real!

It does give us data to help understand Black Holes. 

It gives us an opportunity to verify and test GR.

The algorithm is the process used to evaluate.

 

50 minutes ago, Cassel said:

How would it work in this case?

I am not at a level to answer in all honesty. I am struggling a bit with this also. See my previous post.

[Cassel]

1 hour ago, Delay said:

...Which got the information based on real world observations. The algorithms simply put all the pieces together to form an image.

According to your logic any composite is also not a real image since they're also pieced together by an algorithm. Say goodbye to Curiosity's selfies then, they're not photos apparently!

 

Artist's impressions are just that: artist's impressions.

photograph - ...is based on the Greek φῶς (phos), meaning "light," and γραφή (graphê), meaning "drawing, writing," together meaning "drawing with light."

https://en.wikipedia.org/wiki/Photograph

It all depends on how the algorithm works, what pieces it matches and how it filled the gaps in the observations. This bold statement is closer to definition of rendering than the definition of photo.
https://en.wikipedia.org/wiki/Artistic_rendering

"Artist's impressions are often created to represent concepts and objects that cannot be seen by the naked eye" - So, just like our "photo" of the black hole?
https://en.wikipedia.org/wiki/Artist's_impression

It's ridiculous that scientists do not understand English to such an extent that they confuse a picture with artistic impression ... how should we read their scientific work, if they make such basic mistakes?

In other threads I wrote that "junk DNA" has a misleading name. Well now I can add another misleading item to my list.

Edited April 13, 2019 by Cassel

[Cassel]

24 minutes ago, Starstruck69 said:

I think i understand your angle here. The point is nothing can be measured or observed from this as it is just a humans visualisation from an artists best guess using physics a basic guide. Still valuable though in my opinion it can help some people visualise a BH. Ultimately it generates no data for us. I get your point though and agree with you on a certain level.

I did not write that it is useless, only that I am skeptical about conclusions others made in 5 minutes. Because there are so many things where one small mistake could change the meaning of the whole experiment.
What data? After all, from this "photo" it does not appear that this is a black hole, the expectations of physicists were different than what they observed.

24 minutes ago, Starstruck69 said:

Define real!

It does give us data to help understand Black Holes. 

It gives us an opportunity to verify and test GR.

The algorithm is the process used to evaluate.

Real - actually existing as a thing or occurring in fact; not imagined or supposed.

The object we have observed is real, but whether this object is a black hole or something else is our guess (supposition), based on our limited knowledge.
 

24 minutes ago, Starstruck69 said:

 

I am not at a level to answer in all honesty. I am struggling a bit with this also. See my previous post.

Gravitational lensing from what I understand is more likely to be the case if there was an obstacle between us and the object.

[YNM]

21 hours ago, Cassel said:

In this way, physicists believe that a black hole should look like


That picture doesn't account for red- and blueshifting, probably due to limited time when it was simulated (or it'd make for a better visual).

A more accurate representation :

... which is almost exactly what we see.

Edited April 13, 2019 by YNM

[cubinator]

21 hours ago, Cassel said:

Can you see the difference? I see the difference.
Now the question is whether the object is a black hole or something else? Or is this the way the black holes looks in reality, but the hypothesis that say how the black hole is supposed to look are wrong?

The difference is that the one in the movie is seen almost edge on, while the picture we see in reality is almost face on - we already know as much from observing the huge jets emitted from there. If you were to travel there to it's side, you would see something more similar to the movie.

2 hours ago, Cassel said:

It is not real because it was generated by a computer based on algorithm.

Your eyes are no different.

[Starstruck69]

1 hour ago, Cassel said:

The object we have observed is real, but whether this object is a black hole or something else is our guess (supposition), based on our limited knowledge.

What were you expecting to see?

[Cassel]

1 hour ago, YNM said:

That picture doesn't account for red- and blueshifting, probably due to limited time when it was simulated (or it'd make for a better visual).

A more accurate representation :

... which is almost exactly what we see.

Look closer

 

[Cassel]

1 hour ago, Starstruck69 said:

What were you expecting to see?

I do not expect anything, that's what it's all about to do the observation first and then try to explain it with an open mind. When you assume what you want to see in advance, then you succumb to your own beliefs and see what you want and not what is there.

[Starstruck69]

2 hours ago, Cassel said:

After all, from this "photo"

Its not a photo as such. I think image better describes it.

[YNM]

18 hours ago, Cassel said:

Look closer

Why, no picturesque disc ?

Remember that the disc is very thin from the side. Not to mention we might see it pole-on, which we know M87 is almost is, thanks to relativistic jet tails emanating from it's poles :

It might looks edge-on, but trust me that jet misses us by only tens of degrees - hence you can't see the jet in the other direction.

Edited April 14, 2019 by YNM