[mad aetherist]

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.

[Bored chemist]

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

[evan_au (OP)]

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.

[mad aetherist]

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.

[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.

[Janus]

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.

[Petrochemicals]

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.

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.

[evan_au (OP)]

For a lighter view of the Event Horizon Telescope results, see:
https://www.pocket-lint.com/gadgets/news/147735-best-black-hole-memes

[Kryptid]

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?

[evan_au (OP)]

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.

[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).

[mad aetherist]

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.

[chris]

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.

[mad aetherist]

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?

[evan_au (OP)]

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)?

[geordief]

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?

[evan_au (OP)]

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.

[geordief]

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?

[evan_au (OP)]

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

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 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

[yor_on]

https://www.space.com/first-black-hole-photo-by-event-horizon-telescope.html