Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: evan_au on 07/04/2019 22:55:48

Title: What will the Event Horizon Telescope reveal?
Post by: evan_au on 07/04/2019 22:55:48
There is a massive, multi-continent/multi-time-zone press conference planned for April 9/10 this week, to announce the results of the Black Hole telescope, attempting to take an image of the supermassive black hole at the center of our galaxy.

It is a challenging task - if it had been an abject failure, a small press conference would have been adequate...Along with a request for a bigger grant involving more telescopes...

They have taken measurements over a period of months, so any short term variations (on the order of minutes, hours and days) will be turned into a blur.

So, did they:
- Find one black hole, or are there more lurking there?
- Did it (or they) have an active accretion disk?
- Were there polar jets visible?
- What direction were the polar jets (are they pointing in our direction)?
- What is your guess?

See, for example: https://www.abc.net.au/news/2019-04-07/black-hole-first-ever-photograph-could-be-unveiled-this-week/10979244

All will be revealed, this week! Then we can discuss it here...
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Halc on 08/04/2019 00:28:01
- What direction were the polar jets (are they pointing in our direction)?
How could they be pointed any other way than generally out of the plane of the galaxy?  The average angular motion of 4 million stars has to have an axis similar to the rest of the galaxy, no?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 08/04/2019 01:15:52
There is a massive, multi-continent/multi-time-zone press conference planned for April 9/10 this week, to announce the results of the Black Hole telescope, attempting to take an image of the supermassive black hole at the center of our galaxy.

It is a challenging task - if it had been an abject failure, a small press conference would have been adequate...Along with a request for a bigger grant involving more telescopes...

They have taken measurements over a period of months, so any short term variations (on the order of minutes, hours and days) will be turned into a blur.

So, did they:
- Find one black hole, or are there more lurking there?
- Did it (or they) have an active accretion disk?
- Were there polar jets visible?
- What direction were the polar jets (are they pointing in our direction)?
- What is your guess?

See, for example: https://www.abc.net.au/news/2019-04-07/black-hole-first-ever-photograph-could-be-unveiled-this-week/10979244

All will be revealed, this week! Then we can discuss it here...
How might they be able to see that there is an Einsteinian blackhole?
It might be some other kind of blackhole.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 08/04/2019 09:55:03
Quote from: Halc
How could they be pointed any other way than generally out of the plane of the galaxy?
That is true if our galaxy were isolated in space.

But our galaxy has merged with a number of dwarf galaxies, each with their own central black hole, and each with their own angular momentum. More dramatically, our galaxy is expected to merge with the Andromeda galaxy in the future.

When the supermassive black holes merge, the merged black hole will have quite a different angular momentum than the original, and the polar axis will change.

This has been seen in space, where the angle of the polar jets change suddenly (and symmetrically).

See: https://en.wikipedia.org/wiki/X-shaped_radio_galaxy
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 10/04/2019 00:25:44
Astronomers are hoping that they will be able to see a silhouette of the boundary of where Einstein's General Relativity meets Quantum theory.

We know that these two theories aren't compatible in the region of space near an event horizon. The shape of the event horizon will assist deciding between several different theories which attempt to resolve this major conflict which has dogged physics for almost a century.

Astronomers are also searching for any pulsars near the event horizon, as these would provide a powerful probe of the shape of space near a supermassive black hole.

For more details (and some short videos), see:
https://eventhorizontelescope.org/

For links to live-streaming sites (in a variety of languages), see:
https://eventhorizontelescope.org/blog/media-advisory-first-results-event-horizon-telescope-be-presented-april-10th
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 10/04/2019 20:34:41
Well, it appears that at this stage, the EHT team have only released an image of the supermassive black hole at the center of the M87 galaxy.

The image is rather blurry. M87 is much further away than the supermassive black hole in the center of our galaxy (55 million light-years vs 26 thousand light-years). But it is also much bigger (6 billion times the mass of the Sun vs 4 million times the mass of the Sun).

M87 is known to have an active polar jet produced by the central black hole - which implies that it is actively accreting matter, and this would produce a bright backdrop against which to view the central black hole.
See: https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_hole

On the other hand, our own galactic black hole does not currently have a strong polar jet, which might imply that it is currently on a diet. If there is no active accretion disk emitting lots of radiation, then it  will be hard to image this black hole, despite the fact that it is much closer.

But I am sure the EHT team are still working on the data for our own galactic black hole...
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Kryptid on 10/04/2019 20:41:59
I'm almost giddy at this news. It's amazing that we were actually able to get this image. I can't wait for the picture of Sagittarius A*.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 10/04/2019 21:56:41
Because the Schwarzschild radius of a black hole is proportional to the mass of the black hole, the increased distance and the increased mass almost cancel out.

So the resolution required to image the M87 black hole is almost the same as that required to image the Milky way black hole.
See: https://en.wikipedia.org/wiki/Schwarzschild_radius
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 10/04/2019 22:01:25
Quote from: mad aetherist
How might they be able to see that there is an Einsteinian blackhole?
With this first crude image, Einstein's theory of General Relativity seems to stand up.

The low resolution does not get us close enough to the event horizon to see any deviations due to quantum effects.
- In particular, with this 6 billion solar mass black hole, any Hawking radiation would be at an extremely low temperature (which provides a good silhouette against the extremely hot accretion disk).
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 10/04/2019 22:55:18
Quote from: mad aetherist
How might they be able to see that there is an Einsteinian blackhole?
With this first crude image, Einstein's theory of General Relativity seems to stand up.

The low resolution does not get us close enough to the event horizon to see any deviations due to quantum effects.
- In particular, with this 6 billion solar mass black hole, any Hawking radiation would be at an extremely low temperature (which provides a good silhouette against the extremely hot accretion disk).
Yes -- i think i have mentioned in New Theories that there might be 8 kinds of blackhole (including dark matter blackholes).

Polar jets at M87 would of course support my centrifuging of aether theory which i have mentioned in New Theories.  Are the M87 jets magnetic or something else?
I think that magnetic jets can form anywhere, & polar jets should be rare (are they?).
How do they know they are polar?
Are the jets emitted from inside the Schwarzchild radius, or from outside?
Or are the jets entering?

Are the M87 jets due to accretion?
In which case i would expect the jets to be going inwards, at the poles. But if so then the jets wouldnt be a disc, a disc would i think be an equatorial thing. But i suppose that if the orbiting dust etc is mostly in the equatorial plane then that is where it is most likely to arrive.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Bored chemist on 11/04/2019 11:19:42
Polar jets at M87 would of course support my centrifuging of aether theory which i have mentioned in New Theories. 
At best, they may be not inconsistent with it.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 11/04/2019 12:15:46
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 11/04/2019 12:22:45
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
John Michell in 1783 predicted super massive dark stars that trapped light.  He didnt mention GR. He didnt mention a singularity. Stupid i guess.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Bored chemist on 11/04/2019 13:13:21
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
John Michell in 1783 predicted super massive dark stars that trapped light.  He didnt mention GR. He didnt mention a singularity. Stupid i guess.
It's not an intrinsically complex or relativistic idea (as you have pointed out)
Once you have  the understanding of orbits and escape velocities, and a knowledge of the speed of light, you can work out that a big enough (dense enough) thing won't let light escape.

Newton just missed it; he died 1727 but the speed of light was measured in 1728.
I guess John Michell  didn't want to speculate about what would happen.
That's sensible of him. At the time, practically nothing was known about how stars worked. They didn't know what they were made of, not what kept them hot.
So what?

Why would you call that "stupid"?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Janus on 11/04/2019 16:33:15
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
John Michell in 1783 predicted super massive dark stars that trapped light.  He didnt mention GR. He didnt mention a singularity. Stupid i guess.
It's not an intrinsically complex or relativistic idea (as you have pointed out)
Once you have  the understanding of orbits and escape velocities, and a knowledge of the speed of light, you can work out that a big enough (dense enough) thing won't let light escape.

Newton just missed it; he died 1727 but the speed of light was measured in 1728.
I guess John Michell  didn't want to speculate about what would happen.
That's sensible of him. At the time, practically nothing was known about how stars worked. They didn't know what they were made of, not what kept them hot.
So what?

Why would you call that "stupid"?
The wave model for light hadn't taken hold yet either, not until the Thomas Young double slit experiment revealed it in 1801.
So Michell was also assuming the corpuscular model for light.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 11/04/2019 23:02:55
Quote from: Mad Aetherist
John Michell in 1783 predicted super massive dark stars that trapped light
About 12 years after Michell, the French mathematician Laplace independently predicted black holes.
- 3 years later, Laplace provided a mathematical proof of their possibility.
- His proof shows that he was thinking in terms of light as particles with some velocity.
- The concepts of the energy of a photon and the mass of a photon only arrived with quantum theory, otherwise Laplace could have made a similar prediction based on the energy of light particles.

See: http://www.narit.or.th/en/files/2009JAHHvol12/2009JAHH...12...90M.pdf
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 12/04/2019 02:52:30
Quote from: Mad Aetherist
John Michell in 1783 predicted super massive dark stars that trapped light
About 12 years after Michell, the French mathematician Laplace independently predicted black holes.
- 3 years later, Laplace provided a mathematical proof of their possibility.
- His proof shows that he was thinking in terms of light as particles with some velocity.
- The concepts of the energy of a photon and the mass of a photon only arrived with quantum theory, otherwise Laplace could have made a similar prediction based on the energy of light particles.

See: http://www.narit.or.th/en/files/2009JAHHvol12/2009JAHH...12...90M.pdf
Thanx for that link.
Michell using a ballistic calculation said the Sun would be a dark star if 497 times larger (ie 122,763,473 solar masses). My ballistic calculation based on modern numbers says 485.3.
Here i didnt need GR nor a silly singularity.

I allso using ballistics calculated that we would have a dark star if the same size as Earth & 2156 solar masses.
This reduces to 1079 solar masses if i use GR to calculate the kmps of the slowed light near this dark star. Here i inserted the escape velocity into the equation for gamma.
This reduces to 779 solar masses if i assume that the dark star has an atmosphere with n=1.33 (ie like water), ie slowing the escaping light in that proportion.

Anyhow there is no need for GR or for a singularity. And simple ballistics is good enuff.
So, how will we detect whether a blackhole is a Michellian dark star, or is a Laplacian invisible body, or is an Einsteinian blackhole?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Petrochemicals on 12/04/2019 03:00:38
Has it given an idea of the shape, ie , domed, sphere cone etc ? Or is the resolution and gravity just not good enough ?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 12/04/2019 03:11:16
The wave model for light hadn't taken hold yet either, not until the Thomas Young double slit experiment revealed it in 1801.
So Michell was also assuming the corpuscular model for light.
I suppose that the wave model would need a smaller mass than the ballistic (corpuscular) model.  Based on the wave model suffering a slowing due to the nearness of mass, ie as per Einstein's GR (ie inserting the escape velocity into the equation for gamma). Or is the wave model more complicated than that?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 12/04/2019 03:15:05
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
John Michell in 1783 predicted super massive dark stars that trapped light.  He didnt mention GR. He didnt mention a singularity. Stupid i guess.
It's not an intrinsically complex or relativistic idea (as you have pointed out)
Once you have  the understanding of orbits and escape velocities, and a knowledge of the speed of light, you can work out that a big enough (dense enough) thing won't let light escape.

Newton just missed it; he died 1727 but the speed of light was measured in 1728.
I guess John Michell  didn't want to speculate about what would happen.
That's sensible of him. At the time, practically nothing was known about how stars worked. They didn't know what they were made of, not what kept them hot. So what?  Why would you call that "stupid"?
I agree with Michell, GR is not needed (alltho i think that GR does come into play)(the nearness of mass slows the photons), & a singularity aint needed (& i dont believe in a singularity).
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 12/04/2019 03:38:38
The Wikipedia article mentions that the jet is only seen on one side of the galaxy (our side). A jet on the other side is not excluded, as most of the energy will be directed away from us due to relativistic beaming. It would be hard to see it through the dense population of stars at the center of M87.

At radio wavelengths, symmetrical jets are seen.

It also says that the Jet is at right-angles to the plane of the accretion disk.
- And that the accretion disk is gaining about 80 Earth masses per day (as an average)

If you imagine Saturn as a black hole, the Saturn's rings are the accretion disk (around the equator), and the jet scomes out the North and South poles.

So that should halve the number of models you have put on the table....
See: https://en.wikipedia.org/wiki/Messier_87#Jet
Most of my kinds of blackholes are probly more properly called dark stars because they are made of dark matter & can have little mass.  And i reckon that dark matter resides in the center of all planets etc.  My dark matter is very very dense, it is not atomic, it is more like the neutrons in a neutron star.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Bored chemist on 12/04/2019 07:25:14
I suppose that the wave model would need a smaller mass than the ballistic (corpuscular) model.
As is so often the case, you suppose wrongly.
The escape velocity for a ballistic missile at the event horizon is C
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 12/04/2019 09:40:14
Quote from: Petrochemicals
Has (the EHT) given an idea of the (M87 black hole) shape, ie , domed, sphere cone etc ?
All it can say is that the silhouette is roughly circular, from our viewpoint.

The prediction of General Relativity is that the event horizon is spherical (maybe with an equatorial bulge if the black hole is rotating rapidly). The observation of M87 is consistent with this theory.

A cone or dome (hemisphere) would not be an expected shape for the event horizon, since some parts are much closer to the central point than others.

A sphere (or an ellipsoid for a rotating black hole) has all points of the event horizon at the location where the escape velocity "to infinity" equals the speed of light, c. These points are all at roughly the same distance from the central singularity.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 12/04/2019 11:41:45
I suppose that the wave model would need a smaller mass than the ballistic (corpuscular) model.
As is so often the case, you suppose wrongly.
The escape velocity for a ballistic missile at the event horizon is c.
Yes i am ok with there being a ballistic event horizon, where the ballistic escape velocity is c kmps. Based on the ballistic model being true.

But i believe in a modified ballistic model. Here a photon follows a ballistic traject, but not for simple ballistic reasons, it follows a ballistic traject for aetheric reasons which i wont go into here.  The difference numerically is due to the Einsteinian idea that light is slowed near mass, but that there slowing is not due to Einstein's GR it is due to a photaeno-drag reason which i wont go into here (but am happy to call it a GR effect anyhow)(Einstein possibly deserves some credit here)(albeit for the wrong underlying theory)(which is called equivalence)(nothing to do with the so-called elevator equivalence)(that is another equivalence entirely)(which i wont go into here). 

Anyhow by adding a GR slowing effect it means that, to make an event horizon, a dark star or a blackhole etc can be less massive than praps thort.

However i suspect that the Einsteinologists invent all kinds of observers & then dont remember who is looking up who & who is paying, & Einsteinologists start saying that the light goes straight & it is spacetime that is bent, or that light is not actually slowed near mass but it is the observer's clocks that are slowed, or that it is the lights internal clock, or that Walmart's cheap made in China tapes are easily contracted by relative velocity or something.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Petrochemicals on 12/04/2019 16:20:22
Quote from: Petrochemicals
Has (the EHT) given an idea of the (M87 black hole) shape, ie , domed, sphere cone etc ?
All it can say is that the silhouette is roughly circular, from our viewpoint.

The prediction of General Relativity is that the event horizon is spherical (maybe with an equatorial bulge if the black hole is rotating rapidly). The observation of M87 is consistent with this theory.

A cone or dome (hemisphere) would not be an expected shape for the event horizon, since some parts are much closer to the central point than others.

A sphere (or an ellipsoid for a rotating black hole) has all points of the event horizon at the location where the escape velocity "to infinity" equals the speed of light, c. These points are all at roughly the same distance from the central singularity.
Yet blackholes can , and M87 does have jets which came as a suprise, so the shape of a black hole, and mostly all about them seem to be conjecture and hypothesis. A photo is worth a thousand words, that is if that thousand words are right.

I would expect some sort of parabolic cone with a missing central point where jets as like a ruptured sphere fabric spewing water, or the pressure gradient there of.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Janus on 12/04/2019 16:58:01
Quote from: Petrochemicals
Has (the EHT) given an idea of the (M87 black hole) shape, ie , domed, sphere cone etc ?
All it can say is that the silhouette is roughly circular, from our viewpoint.

The prediction of General Relativity is that the event horizon is spherical (maybe with an equatorial bulge if the black hole is rotating rapidly). The observation of M87 is consistent with this theory.

A cone or dome (hemisphere) would not be an expected shape for the event horizon, since some parts are much closer to the central point than others.

A sphere (or an ellipsoid for a rotating black hole) has all points of the event horizon at the location where the escape velocity "to infinity" equals the speed of light, c. These points are all at roughly the same distance from the central singularity.
Yet blackholes can , and M87 does have jets which came as a suprise, so the shape of a black hole, and mostly all about them seem to be conjecture and hypothesis. A photo is worth a thousand words, that is if that thousand words are right.
Where did you get the idea that the jets for this BH came as a surprise?  They were detected by the Hubble way back in '99.  They were fully expected.  Such jets are produced by in-falling material being redirected and accelerated by the the magnetic field of the BH, this all happens well outside the event horizon.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Petrochemicals on 12/04/2019 17:09:22
Where did you get the idea that the jets for this BH came as a surprise?  They were detected by the Hubble way back in '99.  They were fully expected.  Such jets are produced by in-falling material being redirected and accelerated by the the magnetic field of the BH, this all happens well outside the event horizon.

Quote
The first astrophysical jet was discovered in 1918 by the American astronomer Heber Curtis, who noticed “a curious straight ray … apparently connected with the nucleus by a thin line of matter” in giant elliptical galaxy M87.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 12/04/2019 22:11:40
For a lighter view of the Event Horizon Telescope results, see:
https://www.pocket-lint.com/gadgets/news/147735-best-black-hole-memes
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Kryptid on 12/04/2019 22:12:56
Could the Event Horizon Telescope be used to give us high resolution images of other objects in space besides supermassive black holes? Are there any plans to do this?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 12/04/2019 22:21:52
A few interesting snippets on the logistics:
- The observations were made by 8 radiotelescopes, in April 2017
- April was selected, as this is the month which has the best chance of good weather at all 8 sites simultaneously (statistically speaking)
- To allow accurate time alignment between the different telescopes, they installed a very accurate atomic clock at each site
- The amount of data was so huge (a Petabyte) that it would have taken too long if they tried to send it via the internet
- So they recorded it on half a ton of hard disks, and air-freighted them back to the central data processing facility

Why M87 was processed first:
- M87 is about 1,000 times more massive than the Milky way black hole
- The Schwarzchild radius is about 1,000 times larger
- So the circumference of the black hole is 1,000 times larger
- And it takes about 1,000 times longer for an orbit of the accretion disk
- The Milky Way accretion disk is orbiting rapidly, and its behavior is changing rapidly. They felt that this would make the analysis more difficult.
- But they are still investigating the data they collected on the Milky Way black hole
- They are planning another data collection run in April 2020, with a few more telescopes, and using higher frequencies/shorter wavelengths. This should give them better resolution.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 13/04/2019 04:11:00
Quote from: Mad Aetherist
John Michell in 1783 predicted super massive dark stars that trapped light
About 12 years after Michell, the French mathematician Laplace independently predicted black holes.
- 3 years later, Laplace provided a mathematical proof of their possibility.
- His proof shows that he was thinking in terms of light as particles with some velocity.
- The concepts of the energy of a photon and the mass of a photon only arrived with quantum theory, otherwise Laplace could have made a similar prediction based on the energy of light particles.

See: http://www.narit.or.th/en/files/2009JAHHvol12/2009JAHH...12...90M.pdf
Thanx for that link.
Michell using a ballistic calculation said the Sun would be a dark star if 497 times larger (ie 122,763,473 solar masses). My ballistic calculation based on modern numbers says 485.3.
Here i didnt need GR nor a silly singularity.

I allso using ballistics calculated that we would have a dark star if the same size as Earth & 2156 solar masses.
This reduces to 1079 solar masses if i use GR to calculate the kmps of the slowed light near this dark star. Here i inserted the escape velocity into the equation for gamma.
This reduces to 779 solar masses if i assume that the dark star has an atmosphere with n=1.33 (ie like water), ie slowing the escaping light in that proportion.

Anyhow there is no need for GR or for a singularity. And simple ballistics is good enuff.
So, how will we detect whether a blackhole is a Michellian dark star, or is a Laplacian invisible body, or is an Einsteinian blackhole?
Michell in 1783 said that the Sun would be a dark star if its diameter were 497 times greater, based on the density not changing (or the density profile not changing)(whatever).

Michell didnt explore the possibility that the Sun might become a dark star if its diameter were reduced,
 based on the mass not changing (& the density profile not changing i think). 

I found that using simple ballistic calculations the Sun will become a dark star if its radius is reduced to 2.954 km. Here the escape velocity has to be greater than c kmps.
This increases to 5.907 km if i take into account that the nearness of the Sun slows light, as predicted by Einstein. Here i used GR to calculate the kmps of the slowed light near the Sun, by inserting the escape velocity into the equation for gamma (here c kmps reduces to say c' kmps).
This increases to 8.179 km if in addition to the slowing i assume that the Sun has an atmosphere (corona) with n=1.33 (ie like water), ie slowing the escaping light in that proportion (here c' kmps reduces to c" kmps).
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 13/04/2019 05:07:08
Here is some written krapp from youtube.................
IT'S dark heart sucks all light and life within reach into an unknown dimension at unimaginable speed... but enough about Brexit - look at this first ever picture of a black hole!
All objects suck all light & life within reach into themselves. The Moon does, but its influence might extend to only say 1mm.  There is no unknown dimension, & there is no need here for an unknown dimension. It is an invented image, not a photo. I think c kmps is not unimaginable, its only 300,000 kmps.
The groundbreaking snap was captured by space scientists using telescopes across the planet in a find that experts have boasted is "a huge breakthrough for humanity".
I dont like snap. I dont like find. We can add this to all of the breakthroughs that have not been for humanity.
The black hole, described by scientists as a "monster", is 24billion miles across - 3million times the size of the Earth.
I wonder whether the black hole is the black area or whether it is the size of the invisible mass, ie the dark star. However an Einsteinian blackhole is supposed to be a singularity with no size or zero size. Or praps the size of a blackhole is the Schwarzschild radius (which i think they say is 1/2.6 the diameter of the black area).   
Sitting about 300 million trillion miles away from our planet, it was photographed by a network of eight telescopes across Earth known as the Event Horizon telescope. When used together, the telescopes have the power of a single telescope "the size of our planet", scientists said. The Event Horizon Telescope has been carrying out an international mission to photograph a black hole and its first results were presented at a conference this afternoon...
There must be a better word than sitting. Standing.  Lying. Laying. Floating. Hanging. Why say our planet, why not just say Earth.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: chris on 13/04/2019 09:51:42
Sorry to but-in on this extremely valuable thread, but I wanted to let you all know that Cambridge astronomer Carolyn Crawford is coming onto the Naked Scientists this week to review this story and to update the coverage that it has received.

This is an opportunity for us to address some of the outstanding questions highlighted by other news coverage and also to clarify queries that have surfaced from the reporting.

If you would like to suggest some questions that we can put to Carolyn tomorrow as part of the discussion, it would be lovely to hear them.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: mad aetherist on 13/04/2019 11:31:02
Sorry to but-in on this extremely valuable thread, but I wanted to let you all know that Cambridge astronomer Carolyn Crawford is coming onto the Naked Scientists this week to review this story and to update the coverage that it has received.

This is an opportunity for us to address some of the outstanding questions highlighted by other news coverage and also to clarify queries that have surfaced from the reporting.

If you would like to suggest some questions that we can put to Carolyn tomorrow as part of the discussion, it would be lovely to hear them.
I have a few questions.........
(1) How many kinds of blackhole are there?
(2) How many of these involve a singularity?
(3) How many dont?
(4) Can the event horizon team rule out the existence of any of these kinds at M87 & at Sagitarius A*?
(5) In particular do (1234) support Michell's supersized dark star?
(6) In particular do (1234) support Laplace's supermassive invisible object?
(7) Can non-singularity blackholes or non-singularity dark stars or non-singularity invisible objects have an event horizon?
(8 ) Is the speed of light slowed to nearly 00 kmps near an event horizon? (for a far-away outside observer).
(9) Is the speed of light slowed to 00 kmps inside an event horizon? (for a far-away outside observer).
(10) Is there a maximum mass for a blackhole or for a dark star etc?
(11) Does spin or angular momentum inside the event horizon affect the event horizon?
(12) Does (11) affect the image of the blackhole (or dark star)(or invisible object)?
(13) Do the images prove that Einsteinian blackholes exist, & that singularities exist, & that spacetime exists, & that gravity is the bending of spacetime?
(14) Can such images possibly prove that Einsteinian blackholes exist, & that singularities exist, & that spacetime exists, & that gravity is the bending of spacetime?
(15) What is the possibility that there is a small blackhole etc orbiting close to the big blackhole etc?
(16) What is the possibility that the big blackhole etc is actually a big binary?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 13/04/2019 23:36:19
Some more questions for your guest (if I'm not too late):
- What sort of temperatures did they observe in the accretion disk (the whiter sections and the orange sections)?
- Is the pressure and temperature in an accretion disk sufficient to cause significant amounts of nuclear fusion?
- Why didn't they see any jets in this image? (These jets are present in visible light and radio frequencies)
- Where do jets come from?
- Why do black holes have spin (angular momentum)? What are its effects, and how would you measure it?
- There have been discussions about different theoretical ways to resolve the conflict between quantum theory and general relativity near a black hole. Steven Hawking produced a theory involving Hawking Radiation. What other serious theories are out there, and how could they be distinguished with a closer look at a black hole?
- How much observing time did it take to produce this image of M87?
- Have they collected more data on M87 that they haven't processed or published yet? (I expect that the field of view of each individual telescope would have encompassed most of the galaxy - but maybe not for the telescope arrays).
- When might we see an image of Sgr A* (the black hole at the center of our galaxy)?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: geordief on 14/04/2019 11:07:44
Is there any way we can know anything related to mass distribution inside the Black Hole?(ie the event horizon?)

Do images like this one help?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 14/04/2019 11:48:37
Quote
Is there any way we can know anything related to mass distribution inside the Black Hole?(ie the event horizon?)
Einstein's relativity suggests that any matter or radiation passing the event horizon is on a one-way path to a singularity at the center. That means we cannot send a probe to look inside and then report back.

For astronomical bodies with an internal distribution of mass (like a planet), we can investigate the internal distribution of mass by closely tracking the orbit of satellites. We could try a similar experiment with objects orbiting a black hole.
- We would have to try one without an accretion disk, as the friction, turbulence and magnetic fields within the plasma of the accretion disk will also distort the orbits.

Title: Re: What will the Event Horizon Telescope reveal?
Post by: geordief on 14/04/2019 12:39:53
Einstein's relativity suggests that any matter or radiation passing the event horizon is on a one-way path to a singularity at the center. That means we cannot send a probe to look inside and then report back.

For astronomical bodies with an internal distribution of mass (like a planet), we can investigate the internal distribution of mass by closely tracking the orbit of satellites. We could try a similar experiment with objects orbiting a black hole.
- We would have to try one without an accretion disk, as the friction, turbulence and magnetic fields within the plasma of the accretion disk will also distort the orbits.


Might light count as one of these objects ,as I understand that there is a certain radius where light can  orbit the BH?

 Since the only mass distribution asymmetry  that I can imagine could be between the "perimeter area" and the "central area" how could the orbits of any objects reveal this?

If the Earth was completely spherical,homogeneous  and hollow save for a thin crust ,how would orbiting satellites distinguish this from an Earth where the  mass was evenly distributed  from centre to surface?

I think I have gathered from some that even to speculate along these lines is pointless as ,apparently a Black Hole is  nothing more than a distortion of space time..... although could the shape of this distortion be probed in a similar way ,perhaps?
Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 14/04/2019 22:21:15
Quote from: geordief
I understand that there is a certain radius where light can  orbit the BH?
Yes, the photon sphere defines the innermost stable orbit for light.
Slightly outside that, there are orbits where light can travel 1, 2, 3 or more times around the black hole.
See: https://en.wikipedia.org/wiki/Photon_sphere

Quote
If the Earth was completely spherical,homogeneous  and hollow save for a thin crust ,how would orbiting satellites distinguish this from an Earth where the  mass was evenly distributed  from centre to surface?
Newton's shell theorem (https://en.wikipedia.org/wiki/Shell_theorem) states that, to an outside observer, a thin crust is indistinguishable from a singularity of the same mass at the center.

However, if mass is distributed between the surface and the center, it may not be entirely uniform and spherically symmetric. This will distort the path of a spacecraft. The Juno spacecraft will investigate the internal structure of Jupiter. 
See: https://en.wikipedia.org/wiki/Juno_(spacecraft)#Scientific_instruments

Even more sensitive, a pair of spacecraft in the GRAIL mission mapped the interior structure of the Moon.
See: https://en.wikipedia.org/wiki/GRAIL
Title: Re: What will the Event Horizon Telescope reveal?
Post by: yor_on on 15/04/2019 19:12:45
https://www.space.com/first-black-hole-photo-by-event-horizon-telescope.html
Title: Re: What will the Event Horizon Telescope reveal?
Post by: chris on 15/04/2019 19:27:14
(https://static.projects.iq.harvard.edu/files/styles/os_files_xlarge/public/eht/files/20190410-78m-800x466.png?m=1554877319&itok=m0gPFSet)

Here's the special podcast featuring Cambridge University's Carolin Crawford, from the Institute of Astronomy, updating the details of the EHT findings and answering some of the questions raised here on the forum

https://www.thenakedscientists.com/podcasts/short/eht-sheds-light-m87-black-hole
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Bill S on 15/04/2019 19:48:15
I've not had time to read this thread, but this might be an addition.

https://profmattstrassler.com/2019/04/15/the-black-hole-photo-what-are-we-looking-at/#more-10268

Title: Re: What will the Event Horizon Telescope reveal?
Post by: evan_au on 01/05/2019 10:37:18
A stellar-mass black hole V404 Cygni has been imaged while eating matter from an orbiting star. This used multiple radiotelescopes - but with less resolution than the Event Horizon telescope.

With a mass of around 9 times the mass of the Sun, the accretion disk around this black hole changes very quickly (much faster than a galactic black hole), so astronomers made a movie over 4 hours.

This appears to show matter being ejected at relativistic speeds along the polar axis in bursts, rather than continuously.

See: https://www.space.com/black-hole-wobbling-jets-warp-spacetime.html
Title: Re: What will the Event Horizon Telescope reveal?
Post by: esquire on 01/05/2019 16:57:05
event horizon, implies that the telescope's primary focus, will be an attempt to determine if there exist a curvature to the Universe.
Title: Re: What will the Event Horizon Telescope reveal?
Post by: Bored chemist on 01/05/2019 19:26:06
event horizon, implies that the telescope's primary focus, will be an attempt to determine if there exist a curvature to the Universe.
Not really,