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Imaging a black hole - the EHT


Green Baron

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Yeah, sounds absurd. But this is about the second try to obtain an image of the vicinity of our galaxy's central black hole Sagittarius A* with the EHT (Event Horizon Telescope), a worldwide conglomerate of radio telescopes working as an interferometer. New telescopes where added and improve the chances of success this time.

So, if you guys and gals find any interesting info on this, why not put it here ? I'd like to suggest to keep it "sciency", if nobody objects :-)

Edit: gathering links:

http://iopscience.iop.org/article/10.3847/0004-637X/817/2/173

https://arxiv.org/pdf/1607.03034v1.pdf

 

 

Edited by Green Baron
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It's pretty cool how we effectively can have a telescope as big as the whole world. I hope we do manage to get some good pics! Is Sagittarius A* really the best candidate for imaging, though? It's angular diameter is apparently about 37 microarcseconds. We know there are black holes much closer and less obstructed, although they are quite a bit smaller.

Edited by cubinator
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17 minutes ago, cubinator said:

It's pretty cool how we effectively can have a telescope as big as the whole world. I hope we do manage to get some good pics! Is Sagittarius A* really the best candidate for imaging, though? It's angular diameter is apparently about 37 microarcseconds. We know there are black holes much closer and less obstructed, although they are quite a bit smaller.

Maybe not, but it's clearly the one scientists want to know about the most, at least within the milky way. Besides, they probably want a black hole with an accretion disk, and I have no idea if any non-supermassive black holes have those.

Edited by wadusher1
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What wavelength (or frequency - I know radio telescopes use frequency) are they going to observe it in ?

2 hours ago, cubinator said:

It's pretty cool how we effectively can have a telescope as big as the whole world.

Russia have a radio-telescope satellite that goes about as far as the Moon, it should be a few times that.

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The telescopes on the EHT work in the millimeter or tenths of a millimeter wavelengths.

Optical telescopes in nanometers (400-700 optical spectrum). Radio waves go up to 10s of centimeters, terrestrial radio meters, infrared is in between the optical and radio spectrum in the micrometer range. The other direction is UV nanometers, X-ray shorter ...

ALMA and south pole telescope participate now, i read. So the site might not be up to date ?

Next year a nice one will be ready, the NOEMA. They have a picture on their site showing the wavelengths of the observable spectra.

It seems to be indeed the resolution that makes Sag A* a best candidate. Not sure whether stellar black holes, though closer, are just too small (10s of km) for observation (or better: for getting a close view), but they mentioned a black hole in M87, which is far away but a real one :-)

Stellar black holes can have accretion discs if they have a close companion. Cygnus X-1 may have one and i am sure others as well as i think (not sure) X-rays are the main reason why they can be detected at all, and X-rays might be emitted by an accretion disc.

Edited by Green Baron
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10 hours ago, wadusher1 said:

Maybe not, but it's clearly the one scientists want to know about the most, at least within the milky way. Besides, they probably want a black hole with an accretion disk, and I have no idea if any non-supermassive black holes have those.

Yeah, any black holes with anything close by will have an accretion disk.

Because an accretion disk is nonspherical, it can produce really interesting habitable zones. A planet closely orbiting a brown dwarf that is itself orbiting a black hole would have a lengthy period of habitability.

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I highly doubt that we can speak of habitability anywhere near an accretion disk around a black hole or neutron star. There is really hard radiation, thermal and x-ray all around that originate from the released potential energy as stuff falls into the black hole / hits the neutron star. I mean really hard :-)

Protoplanetary discs around normal stars are a different thing, i'd say.

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43 minutes ago, Green Baron said:

I highly doubt that we can speak of habitability anywhere near an accretion disk around a black hole or neutron star. There is really hard radiation, thermal and x-ray all around that originate from the released potential energy as stuff falls into the black hole / hits the neutron star. I mean really hard :-)

Protoplanetary discs around normal stars are a different thing, i'd say.

Wouldn't it depend on distance, to some degree? A very large accretion disk could provide fairly constant insolation for a large range of distances.

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I found a huge pile of work on the radiation around black holes and accretion disks, for example in The Astrophysical Journal. But i think Science and Nature have texts as well on this.

I only do not understand everything and right now lack the time ... :-/

Edited by Green Baron
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  • 1 month later...
3 hours ago, Green Baron said:

For those who just want to know why there aren't any cool JPEGs online yet:

Quote

Each observatory records so much data that it can’t be transmitted electronically. Instead, the information from all the telescopes—equivalent to the storage capacity of ten thousand laptops—has been recorded on 1,024 hard drives. The drives must be mailed to the Event Horizon Telescope’s processing centers at MIT Haystack and the Max Planck Institute for Radio Astronomy in Bonn, Germany.

The hard drives from the South Pole telescope can’t be flown out until the end of the winter season there at the end of October.

Once the data reach each processing center, a stack of servers will perform the all-important task of combining the time-stamped signals from the eight observatories.

 

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  • 4 months later...

News:

http://eventhorizontelescope.org/blog/eht-status-update-october-05-2017

Edit: the interesting quote is this one: ".... so we have already confirmed that all the sites in the EHT worked well. "

Apparently mainly problems of algorithms, data preparation and processing and finally image processing until we might pretend to be able to see something :-)

Edited by Green Baron
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  • 2 months later...

More news:

http://eventhorizontelescope.org/blog/eht-status-update-december-15-2017

tl:dr: the discs from the south pole telescope have arrived at Haystack and MPI for Astronomy. Comparison will take 3 weeks, then analysis of the data with no end date given ... days, weeks, months, eons ?

Who knows :-)

Edited by Green Baron
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On 4/3/2017 at 6:42 PM, Green Baron said:

Yeah, sounds absurd. But this is about the second try to obtain an image of the vicinity of our galaxy's central black hole Sagittarius A* with the EHT (Event Horizon Telescope), a worldwide conglomerate of radio telescopes working as an interferometer. New telescopes where added and improve the chances of success this time.

So, if you guys and gals find any interesting info on this, why not put it here ? I'd like to suggest to keep it "sciency", if nobody objects :-)

Edit: gathering links:

http://iopscience.iop.org/article/10.3847/0004-637X/817/2/173

https://arxiv.org/pdf/1607.03034v1.pdf

I read about this a few days ago... I'm super curious to see what happens, and if they can actually get some sort of image... :)

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You cannot see a black hole, when you are looking at a black hole you are actually looking at the structure of space-time around the black hole. The information you gain is not about the black hole, because most of the black holes we observe produce hawking radiation at such a low frequency its hard to detect.

The fine structure of space, the quantum foam, is believed to be distorted to its extreme around a black hole. If we imagine a black hole as a lens, it is possible to see in the lens potential distortion of parallel rays of light passing in very close proximity. In looking from a single telescope one may not be able to resolve distortions caused by the distortion of quantum space-time (hypothetical quantum foam) by using multiple telescopes spread apart at great distances it is possible to see effects of quantum space time on arrival times and photon energies. The evidence that supports further examination of space-time comes from this observation.

" Blazars are likely to originate from matter falling into a black hole and possibly a binary black hole. The velocity dispersion (which is the maximum difference in the velocity toward or away from Earth) observed in the galaxy is 372 km/s which predicts a black hole mass of (0.9 − 3.4) × 109M. However, dispersion of velocity was also measured as 291 and 270 km/s so the central mass may be less.[13] A 23-day variability suggested that an object may be orbiting the central black hole with a 23-day period.[13] " https://en.wikipedia.org/wiki/Markarian_501#Gamma_rays  " The gamma rays from Mrk 501 are extremely variable, undergoing violent outbursts.[5] The gamma ray spectrum of Mrk 501 shows two humps. One is below 1 keV and can be considered to be X rays and the other is above 1 Tev. During flares and outbursts the peaks increase in power and frequency.[5] Flares lasting 20 minutes long with rise times of 1 minute have been measured by MAGIC. In these flares the higher energy gamma rays (of 1.2 Tev) were delayed 4 minutes over the 0.25 TeV gamma rays.[9] This delay has led to various theories, including that space is bigger at small dimensions with a foamy quantum texture.[10] The foam would create a variation in the speed of light for higher-energy light gamma-rays and the lower-energy radio waves and visible light. "

Using Marharian 501 to study quantum foam is like using a GBU-43 MOAB to plow a vegetable garden. Yes is has the photon energies that would distort quantum space-time, the problem is that there is alot going on in a Gamma ray burst from a binary black hole. Again a much more refined way for examining the fine texture of space-time around potential energy wells in space-time is you use many telescopes far apart from each other that look at more carefully studied EM sources,. This is what they are doing.

The importance of quantum space-time and its proof and characterization is extremely important to the bounds of space travel. The tyranny of the speed of light,  direction of entropy, time, dimensionality, and the fundemental forces in the Universe are all effected by the character of quantum space-time, its like 41 of the physical universe. IN the other thread we are discussing how to extract energy efficiently in space without classical electrical generation. This all goes back to entropy, by studying space-time around back holes in 100 or 200 years we may uncover clever ways to extract most or all of the energy from an energy source, making Fusion power in space a thing. If we could do this of course, fusion power would be easy in and of itself.

 

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1 hour ago, PB666 said:

You cannot see a black hole, when you are looking at a black hole you are actually looking at the structure of space-time around the black hole. The information you gain is not about the black hole, because most of the black holes we observe produce hawking radiation at such a low frequency its hard to detect.

Yeah but we can still have our cool picture of a black dot.

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The whole point of the EHT project is to obtain an image of the gravitational lensing around Sagittarius A*, in the X-ray spectrum. They don't expect to see just a black dot. The video that I posted back in May explains quite well in layman's terms how it is being done:

On 13/05/2017 at 9:44 AM, PakledHostage said:

 

(How can we expect everyone in LA to pay attention to launch notices posted by Vandenberg AFB if people on this forum don't even read up thread?)

Edited by PakledHostage
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38 minutes ago, PakledHostage said:

The whole point of the EHT project is to obtain an image of the gravitational lensing around Sagittarius A*, in the X-ray spectrum. They don't expect to see just a black dot. The video that I posted back in May explains quite well in layman's terms how it is being done:

(How can we expect everyone in LA to pay attention to launch notices posted by Vandenberg AFB if people on this forum don't even read up thread?)

I wondered about gravitational lensing... but around a black hole??? What's it going to look like? A target, with circles around the central dot??? 

FYI... haven't watched the video yet...

Edited by Just Jim
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1 hour ago, PakledHostage said:

The whole point of the EHT project is to obtain an image of the gravitational lensing around Sagittarius A*, in the X-ray spectrum. They don't expect to see just a black dot. The video that I posted back in May explains quite well in layman's terms how it is being done:

(How can we expect everyone in LA to pay attention to launch notices posted by Vandenberg AFB if people on this forum don't even read up thread?)

You want to scroll back to May, [Setting time machine in reverse] <ping> . . . .<ping> OK im back,  what was I looking for again?

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