Stargazing Event Horizon Telescope Results Released Yesterday (April 10, 2019)

[mfb]

Media Advisory: Press Conference on First Result from the Event Horizon Telescope
April 10, 15:00 CEST (13:00 UTC. In 8 days and 13 hours)
Livestream links are on that website.

The Event Horizon Telescope is a collection of radio telescopes all over the world which recorded data from the supermassive black hole in the center of the Milky Way. Combining the different data sets leads to a virtual telescope as large as Earth in terms of angular resolution - good enough to resolve the area directly around the black hole.

This article shows some simulations how it might look like.Edit: The first image:

 

[berkeman]

Sorry, what are those simulations supposed to be showing? The SMBH eclipsing a star that is near the center of the MWG? Sorry if I'm missing the obvious...

 

[mfb]

The accretion disk around the black hole - gas and random other stuff orbiting the black hole closely. Brighter: More stuff.

There shouldn't be stars that close. We know one that has a periapsis speed of 3% the speed of light, but that is still outside the range the Event Horizon Telescope is interested in.

 

[m4r35n357]

Hmm, apparently it is "a groundbreaking result from the EHT".

 

[PAllen]

I guess this will expand the horizon of our knowledge...

 

[Greg Bernhardt]

EHT is targeting two black holes, the biggest in the sky from our point of view. The first is Sagittarius A*, the supermassive black hole at the centre of the Milky Way, while the second is an even larger black hole at the centre of the Messier 87 galaxy, found in the constellation Virgo.

https://www.newscientist.com/articl...re-of-a-black-hole-may-be-revealed-this-week/

 

[mishima]

Is this just a first light/data release or is there some accompanying journal article?

 

[mfb]

I'm sure there will be at least a note, but probably a preprint or publication that comes with the press conference.

 

[mfb]

This is in one hour from now!

Livestream e.g. here at ESO.

 

[mfb]

Kind of like the simulations...
Screenshot, poor quality.

Edit: After some color corrections and so on. Left observation, right a theory prediction.

 

[Orodruin]

M87 it is!

 

[Greg Bernhardt]

 

[robphy]

4000x2330 Image available from NSF
https://www.nsf.gov/news/special_reports/blackholes/formedia.jsp

 

[websterling]

The papers are are published in the current The Astrophysical Journal Letters and are available here-
https://iopscience.iop.org/journal/2041-8205

 

[tade]

View attachment 241628

I wonder what the implications for Hawking radiation and other black hole theories are.

Also, there's just too much crap in the way to get a clear shot of Sagittarius right?

 

[websterling]

I wonder what the implications for Hawking radiation and other black hole theories are.

There would be no implications for Hawking radiation. A black hole this massive would essentially have a temperature of absolute zero.

 

[Drakkith]

Amazing picture!

 

[Amrator]

So does this count as the first direct detection of black holes?

 

[aabottom]

Full size 7416x4320 tiff (182.4 MB) available here:
https://www.eso.org/public/images/eso1907a/

 

[Drakkith]

Video from Veritasium on how to understand the image of a black hole:

 

[berkeman]

Sorry for the dumb question (especially if it's already been addressed), but if they used 8 radio telescopes to form this image, where did the visible light colors come from?

https://abc7news.com/science/heres-the-first-ever-direct-image-of-a-black-hole/5241612/

 

[russ_watters]

Cool picture, but what is actually new here? Haven't we already gotten pictures of matter falling into black holes? Is this just cooler because it's circular and black in the middle?

 

[russ_watters]

Sorry for the dumb question (especially if it's already been addressed), but if they used 8 radio telescopes to form this image, where did the visible light colors come from?

Colorization. Somebody picked them.

 

[aabottom]

Video from Veritasium on how to understand the image of a black hole:

This is a very good explanation of what the black hole image shows.

 

[tade]

Colorization. Somebody picked them.

what is the visible spectrum image expected to look like? Based on the physics, I'm guessing almost identical to the radio image?

 

[Orodruin]

Haven't we already gotten pictures of matter falling into black holes?

No.

 

[mfb]

The colors just visualize the intensity of the (radio-wave) radiation. Brighter/yellow: More radiation. Darker/red: Less radiation. It is synchrotron radiation, visible light would come from thermal radiation, it can have a different distribution. Gas clouds between the black hole and us absorb too much visible light.

@russ_watters: It is the first time we see a black hole as more than just a point-like object in the sky.

 

[russ_watters]

No.

I'm really not trying to be difficult, but how is this new image any different from that standpoint, from this one:

@russ_watters: It is the first time we see a black hole as more than just a point-like object in the sky.

So, high enough resolution that we can see a black disk in the middle? Fair enough.

 

[Orodruin]

I'm really not trying to be difficult, but how is this new image any different from that standpoint, from this one:

You are not really seeing the event horizon. You are seeing the products in terms of radiation coming from there but it is a point object so you have not really resolved anything. This image resolves the direct effects near the event horizon.

 

[jedishrfu]

Sorry for the dumb question (especially if it's already been addressed), but if they used 8 radio telescopes to form this image, where did the visible light colors come from?

https://abc7news.com/science/heres-the-first-ever-direct-image-of-a-black-hole/5241612/
View attachment 241632

View attachment 241633

They used a paint-by-numbers kit.

Also the picture kind of looks like a smiley face maybe it knows it'll gobble up our planet sometime in the distant future perhaps and end of simulation for us.

 

[Orodruin]

I had a colleague put a rewriting of the Ring Verse from Lord of the Rings so I had to counter with a limerick:

There once was a black hole named Kevan,
so big and far up in heaven,
in the accretion disk
you'll know you're at risk
to be eaten by M87

Edit: He re-countered so I had to write another one ...

In a galaxy far far away
A long time ago, so they say
An enormous black hole
went out of control
its ring was the unwilling prey

 

[pinball1970]

First story on radio 1 and 2 all day beating Brexit and Israeli elections

 

[virgil1612]

Does the light come from the accretion disk?

 

[davenn]

Does the light come from the accretion disk?

Yes, the generated image of the radio signals that you see are coming from the accretion disk

ohhh and it isn't "light" it isn't optically visible ( that is ... this IS NOT an optical image)...
the radio emissions are at very short microwave radio wavelength, 1.3mm ( frequency ~ 230 GHz)Dave

 

[davenn]

but if they used 8 radio telescopes to form this image, where did the visible light colors come from?

Colorization. Somebody picked them.

yes ... so the brighter the colour, the stronger the radio emissionoops, I see @mfb commented the same

 

[berkeman]

So the real colors could be blues and greens? I guess they used the simulations to figure out what the visible colors would probably be, and tuned the radio telescope false color image to try to match?

 

[virgil1612]

Yes, the generated image of the radio signals that you see are coming from the accretion disk

ohhh and it isn't "light" it isn't optically visible ( that is ... this IS NOT an optical image)...
the radio emissions are at very short microwave radio wavelength, 1.3mm ( frequency ~ 230 GHz)Dave

Yes, but I meant... is that luminous ring the accretion disk, or it's just light coming from there and orbiting the black hole (the photon sphere, that's how it's called?), giving us a sense of the shape of the horizon of the black hole?
Virgil.

 

[davenn]

So the real colors could be blues and greens?

well it's a radio signal so it doesn't have a colour. Just in that 144MHz doesn't have a colour or one that is different from, say, 440 MHz

A radio telescope builds up a pattern of signal intensity to give something that looks like the isobars on a weather chart. The astronomers then use different shades of colours to indicate the intensity of the radio signal. They could have just as easily used dark blue to bright blue/white. Dave

 

[davenn]

Yes, but I meant... is that luminous ring the accretion disk, or it's just light coming from there and orbiting the black hole (the photon sphere, that's how it's called?),
Virgil.

It is the accretion disk
From the EHT www site
https://eventhorizontelescope.org/

The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.

It's not visible light, so not "light" in the way you are thinking of it. It is EM radiation at ~ 230 GHz ( 1.3mm wavelength) a very long way below visible light (much lower frequency and longer wavelength)Dave

 

[berkeman]

well it's a radio signal so it doesn't have a colour. Just in that 144MHz doesn't have a colour or one that is different from, say, 440 MHz

A radio telescope builds up a pattern of signal intensity to give something that looks like the isobars on a weather chart

Yeah, I get that. But how did they map the radio signal frequencies and intensities to those yellows and reds that the popular press is fawning over? Were the simulations earlier in this thread also arbitrary in their color mapping from expected radio emissions, or were they meant to simulate what the visible light emissions would look like?

I'm definitely not meaning to give you and @mfb a hard time at all. Great images. I just prefer to understand where the false color image mappings came from (and I wish astronomy images would be explicitly labeled in the corner "False Color Image" when it's not a true visible light image). Thanks.

 

[davenn]

But how did they map the radio signal frequencies and intensities to those yellows and reds that the popular press is fawning over?

The colours are arbitrary, totally irrelevant to visible light.
darker orange is the lowest intensity radio signal, the brightest colours the strongest signal

I just prefer to understand where the false color image mappings came from

Picked a nice colour ... oranges and shades thereof are aesthetically pleasing to most people
as I said they could have been shades of blue

and I wish astronomy images would be explicitly labeled in the corner "False Color Image" when it's not a true visible light image

you and me both

the number of people on PF and around the net who think these are optical photographs because of the way the press releases have worded it. Us astronomers understand what we are seeing, but the general public are getting easily misled and think that it is optical and not radio telescopes. Because for most people, a telescope is something you look through.D

edited

 

[jedishrfu]

Veritaseum released a new video on it:

 

[Pierre Ordinaire]

Excuse me, but are there not many stars between the black hole and Earth, that should be blocking the view of the black hole?

 

[Orodruin]

Excuse me, but are there not many stars between the black hole and Earth, that should be blocking the view of the black hole?

No. The sky is not as populated as you seem to imagine.

 

[sysprog]

4000x2330 Image available from NSF
https://www.nsf.gov/news/special_reports/blackholes/formedia.jsp

That page uses white text on a black background. I just asked nsf.gov in an email to stop doing that.
To make that page more readable, you can copy and paste the following code into the address bar on your browser, or paste it into a 'bookmarklet' so can you get rid of such color-impairment of readability on any (works on html/css obnoxious colors) page you encounter:

javascript:(function(){var newSS, styles='* { background: white ! important; color: black !important } :link, :link * { color: #0000EE !important } :visited, :visited * { color: #551A8B !important }'; if(document.createStyleSheet) { document.createStyleSheet("javascript:'"+styles+"'"); } else { newSS=document.createElement('link'); newSS.rel='stylesheet'; newSS.href='data:text/css,'+escape(styles); document.getElementsByTagName("head")[0].appendChild(newSS); } })();

The pictures are pretty interesting.

 

[Tom.G]

But how did they map the radio signal frequencies and intensities to those yellows and reds

or were they meant to simulate what the visible light emissions would look like?

It's sort of like asking what the output of an ultrasonic remote control looks like. A frequency-shifted representaion could be used for time-varying data to convert to the audible range, but this Black Hole has spatial signal variation. So they essentially frequency multiplied by a factor of ≈2364 to convert to the visible range of us Humans. Then FM modulated according to intensity (signal strength), just like an FM radio broadcast.

Then the magic occurred when our eyes and brain converted to an image that is somewhat understandable.

Cheers,
Tom

 

[mitchell porter]

I have been searching fruitlessly for a straightforward account of what these pictures show, but the Veritasium videos in #20 and #42 explain it very clearly.

Also, from the papers linked at #14 - paper I, section 4 - I learn that the M87 black hole was observed exactly two years ago. It's interesting that it took so long to process, and that everyone involved maintained a disciplined silence throughout those two years.

 

[DennisN]

A new video about this from one of my favorite channels, Sixty Symbols:

 

[jedishrfu]

And this article on the Comp Sci grad student who helped construct the image from the noisy data:

https://www.sciencealert.com/this-2...lped-bring-us-the-first-image-of-a-black-hole

 

[pinball1970]

Yeah, I get that. But how did they map the radio signal frequencies and intensities to those yellows and reds that the popular press is fawning over? Were the simulations earlier in this thread also arbitrary in their color mapping from expected radio emissions, or were they meant to simulate what the visible light emissions would look like?

I'm definitely not meaning to give you and @mfb a hard time at all. Great images. I just prefer to understand where the false color image mappings came from (and I wish astronomy images would be explicitly labeled in the corner "False Color Image" when it's not a true visible light image). Thanks.

The colours could be are arbitrary? There are other (amazing) images from Hubble of distant galaxies / star nurseries where they overlay infra red and other frequencies out of the visible spectrum. Just so we have a more detailed image of what is there.

Yellow to red could be shorter to longer wavelength? Or difference in intensity.