Questions tagged [event-horizon-telescope]

Questions about the Event Horizon Telescope, or EHT.

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Is this image of Sgr A* correctly labelled?

This BBC article contains this "schematic description" of the EHT Sgr A* image: The source is described only as "EHT Collaboration" and I haven't been able to find the original ...
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10 votes
2 answers
861 views

Why is the ring in this simulation of Sgr A* off center?

In the recent releases of images of Sgr A*, simulated versions of what they expected were included along side the actual images they were able to get. What confuses me about these simulated images (...
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3 votes
1 answer
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Does the newly found orientation of Sgr A* match the theory that the Fermi bubbles might have been caused by jets?

The EHT just announced their great findings about Sgr A*, amongst other cool things they found that we look towards the black hole face on which means that if there is a jet it approximately looks ...
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9 votes
1 answer
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Doubt regarding size and shape of black hole images published by the Event Horizon Telescope (EHT)

The recent publications of the images of black hole shadow by the Event Horizon Telescope collaboration prompts us to study black hole images in more details. According to the no-hair theorem, the ...
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1 vote
0 answers
79 views

Why hasn't the EHT taken an image of Sgr A*?

The Event Horizon Telescope or EHT took an image or the black hole at the center of M87 in 2019, and in 2021 it measured the polarization of the light from M87*. Right after the first image of M87* ...
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5 votes
3 answers
793 views

Can the Event Horizon Telescope been used to find intergalactic distances?

Now that we have the Event Horizon Telescope (EHT), why can't we just guess and check intergalactic distances by changing the EHT's focal length? For instance why don't we take another picture of M87,...
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  • 309
3 votes
1 answer
90 views

How, precisely, do radio astronomers detect (and record) the phases of waves for interferometry?

Interferometry is always in the news, and at radio frequencies it has been for a long time... The popular press always talks about directly 'interfering' two waves as they come in, but can they tell ...
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2 votes
1 answer
182 views

How can light circle a black hole one or more times and then escape again? [duplicate]

The shadow that is cast by a black hole was beautifully captured by the event horizon telescope. A concentration of light in the photon sphere around the hole (adjacent to the event horizon) ...
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3 votes
1 answer
279 views

How will they know when to start taking the picture of the black hole at the center of the Milky Way?

@csm's answer to Why not take a picture of a closer black hole? points out that it's necessary for the supermassive black hole at the center of a galaxy to be actively feeding for it to generate a ...
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4 votes
1 answer
271 views

Will the first Event Horizon Telescope image of the Milky Way's black hole Sgr A* just be another lumpy orange donut?

@HDE226868's answer to Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image? explains that neither black hole is orange and any Event Horizon Telescope ...
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7 votes
1 answer
129 views

Is there any work underway to push the long baseline capabilities of the Event Horizon Telescope to sub-millimeter wavelengths?

The Max Planck Institute for Radio Astronomy's press release Something is Lurking in the Heart of Quasar 3C 279; First Event Horizon Telescope Images of a Black-Hole Powered Jet shows a stunning ...
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4 votes
1 answer
165 views

Why don't we build an interferometer between Earth and the Moon?

The Event Horizon Telescope (EHT) does interferometry from an array of telescopes spread all across Earth. The data is locally stored on a hard drive and shipped to a central location, so the ...
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4 votes
1 answer
154 views

Would the Event Horizon Telescope be able to produce a superior image of Betelgeuse?

Current images of Betelgeuse are already amazing, but I was wondering if the EHT could be able to make a significantly better image, given that Betelgeuse is pretty big and pretty bright?
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1 vote
1 answer
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From whence is the Event Horizon Telescope black hole data available for amateur reconstruction?

Ralf Vandebergh's tweet shows his own reconstruction of an image of the accretion disk around a black hole, generated presumably from Event Horizon Telescope data. I'm assuming that the data came ...
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5 votes
1 answer
108 views

Could images of (very) nearby targets be recovered from Event Horizon Telescope data?

Reading this question I was struck by the fact that the "pointing" of an interferometer is effectively done in the correlator, at least within the common field of view of all the telescopes, which is ...
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  • 9,893
5 votes
1 answer
1k views

Would Hubble Space Telescope improve black hole image observed by EHT if it joined array of telesopes?

My question is related to black hole image released in April. As far as I understand idea of EHT, it joins observations from multiple locations to work like one telescope with radius that is equal to ...
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  • 53
2 votes
2 answers
312 views

If a black hole does not emit light, how can one take a picture of the black hole itself?

There's some discussion that the image composed by the Event Horizons Telescope is really just an accretion disk. To "take an image" of something, you need the light reflecting off of the surface of ...
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  • 282
3 votes
1 answer
264 views

Do the "schwarzschild metric" or the "isotropic metric" fit the Event Horizon telescope data on Messier 87 better?

The "Schwarzschild solution" in "Schwarzschild metric" looks like: $$\text -c^2d\tau^2=-\left(1-\frac{2GM}{rc^2}\right)c^2dt^2+\left(1-\frac{2GM}{rc^2}\right)^{-1}dr^2+r^2(d\theta^2+\sin^2\theta\,d\...
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  • 446
3 votes
1 answer
299 views

What is the actual resolution of Event Horizon Telescope?

I am quite impressed with the recently published image of M87* black hole. It appears that this image achieves spatial resolution well above and beyond what was available until today. But how high ...
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  • 131
1 vote
1 answer
61 views

What do the lines in this Event Horizon Telescope and Global mm-VLBI Array infographic represent?

In the following EHT and GMVA diagram, what do the yellow and blue lines represent? I don't think they're physical communication lines (that would be unfeasible). Do they depict anything specific? ...
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  • 431
11 votes
3 answers
361 views

What else could the Event Horizon Telescope Observe?

The Event Horizon Telescope was made possible in order to observe the details of supermassive black holes. This took a huge amount of work installing extra telescopes and developing the hardware and ...
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  • 9,893
3 votes
1 answer
349 views

Is this the best non-radio image of whatever's at the center of M87? How was it taken?

The BBC News article First ever black hole image released shows the instantly-iconic radio image of the (almost certainly) supermassive black hole at the center of the M87 galaxy, just released by the ...
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41 votes
3 answers
8k views

Why are there uneven bright areas in this photo of black hole?

In the recently released photo of a black hole shown above, which was created by using data from EHT, why is the lower region brighter than the one above? Is it because of the rotation of the ...
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70 votes
5 answers
14k views

Why not take a picture of a closer black hole?

There are closer galaxies than Messier 87 for sure, even ours! It sparked my curiosity that they went with one 53 million light years away. Is there a reason for this?
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3 votes
1 answer
609 views

What is the orientation of the M87 black hole image relative to the jet?

On the image of the M87 black hole released today by the Event Horizon Telescope team, which direction points towards the jet? Is it on the brighter side of the ring? To resolve ambiguity, I'm ...
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1 vote
1 answer
543 views

What does it mean when there are two plus-or-minus signs for a measurement?

As far as I know, the plus-or-minus sign is used to indicate the statistical margin of error of a measurement. But what does it mean when there are two plus-or-minus signs in the same measurement? ...
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  • 431
26 votes
2 answers
8k views

Why didn't the Event Horizon Telescope team mention Sagittarius A*?

At the press conference this morning, the Event Horizon Telescope team didn't say much about Sagittarius A*, which was the target many of us have been waiting for. Is there any explanation anywhere ...
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6 votes
3 answers
346 views

How can the Event Horizon Telescope image Sgr A* when it's not visible from all sites at one time?

I went to https://eventhorizontelescope.org/array and read about the ten sites listed as part of the EHT, I have a mashed-up screen shot of them below. I made a little script also shown below with ...
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6 votes
2 answers
193 views

Is there any update on the Availability of Event Horizon Telescope Images?

There has been no news on the obvious public channels from the EHT project since last (Northern) summer. Does anyone have more information on when any results from the April 2017 run might be released?...
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