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

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A new video about this from one of my favorite channels, Sixty Symbols:
Did he say "its like taking a picture of a gallstone on the moon"?

I read elsewhere the the 40 uarcsecs was like taking the picture of a DVD on the moon.

Here's more on black holes and the prior illustrations used to represent them to the public:

https://www.vox.com/science-and-health/2018/1/8/16822272/black-hole-looks-like-what

and lastly Kip's excellent book on the Science of Interstellar with their computer simulations:

https://www.amazon.com/dp/0393351378/?tag=pfamazon01-20
 
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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.
Yes, this uis one of the reasons kids get disappointed with Astronomy. They see these fantastic images and don't realize that the colors are describing measured data and aren't the actual colors. In fact, in a telescope you'll see only star brightness ie black and white and it just doesn't look like these amazing works of art.
 
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Did he say "its like taking a picture of a gallstone on the moon"?
I heard "golf ball".
 
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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.
They chose a color code that some software package provided, the publication will have some details. You'll find a similar color scheme in many other publications. The simulations used the same scheme, sure.

This has absolutely nothing to do with whatever visible light the accretion disk emits.
 
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Do you think a gallstone is comparable to a golf ball in size? haha

Turns out yes.
Ouch. And if we hit a golf ball into Sagittarius A* would it count as a hole-in-one? :oldconfused:
 

Orodruin

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Do you think a gallstone is comparable to a golf ball in size? haha

Turns out yes.
Fermi estimate it! A golf ball is not order 0.1 cm and not order 10 cm in radius, so order 1 cm. A gall stone is not order 0.1 cm and not order 10 cm in radius, so order 1 cm. The exact same size!
 

russ_watters

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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.
It's totally arbitrary. These colors were probably picked because they "look right", but radio waves are used here because there is little or no visible light to determine a color. Insofar as "color" is just a name for different bands of wavelengths, the "color" of this image is "microwave".

Usually false color images are labeled, but not always, and I agree it is a bit irritating when it is way off. There are a lot of Hubble photos that are visible or near ir where the colors are purposely way off.

Most of my photos are taken in greyscale, with filters. Indeed even a consumer camera gets its color with a grid of filters and software to map the colors to the proper pixels.

For many of my solar photos I used narrow-band Hydrogen Alpha spectral line filter - which is deep red - and mapped it to a yellow I chose because it looked right.

Hydrogen alpha also works really well for the moon by cutting down the glare. So those photos I just leave greyscale since the moon is an almost perfect grey (black) even though I took the images in red light.
 

russ_watters

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FYI, there is actually a defined "Hubble Palette" for color mapping:
...A composite of narrowband image data, the telescopic view captures the characteristic emission from ionized sulfur, hydrogen, and oxygen atoms mapped to red, green, and blue hues in the popular Hubble Palette.


There's a chart in the second one that shows for example the Ha filter, which is red, mapped to Green and the O-III, which is green, mapped to blue.

I suppose it is most common to see wavelengths larger than visible to be red and smaller than visible to be blue in false color images.
 

OmCheeto

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A new video about this from one of my favorite channels, Sixty Symbols:
Did you watch the video on M87 they recommended at the end?
I thought it was interesting that the Earth orbits M87.

M87 - Infinity in your Hand - Deep Sky Videos​
DeepSkyVideos​
Video by Brady Haran​
Published on Oct 9, 2018​
Becky Smethurst discusses the massive and superfreaky M87.​
Recorded with Dr Becky Smethurst as part of the Sixty Symbols Ogden Fellowship at the University of Nottingham.​
"The Earth goes round the Sun
The Sun goes round the Milky Way
The Milky Way goes round the center of the Local Group
And the Local Group goes round the center of the Virgo Supercluster
The center of the Virgo Supercluster is M87
Technically, the Earth is going round M87"
Paraphrased for brevity.​
Livestream e.g. here at ESO.
I wonder how many livestreams there were. I watched both that one, and the following:


National Science Foundation/EHT Press Conference Announcing First Image of Black Hole
National Science Foundation
Published Apr 10, 2019

I found the following information interesting, and somewhat entertaining:
@13:40​
Dan Marrone, AP of Astronomy, Univ of AZ​
"It took 7 days to collect 5 petabytes of data
recorded on >100 toasterish sized modules
HALF A TON of hard drives"​
Just notes I scribbled while watching. "toasterish sized modules" are my words.​

That's a lot of hard drives!
 
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"The Earth goes round the Sun
The Sun goes round the Milky Way
The Milky Way goes round the center of the Local Group
And the Local Group goes round the center of the Virgo Supercluster
The center of the Virgo Supercluster is M87
Technically, the Earth is going round M87"
An very fascinating video! Worthy for posting in "Our Beautiful Universe" thread, so I'll post it there too.
 

DaveC426913

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This is a very good explanation of what the black hole image shows.
Indeed. An excellent explanatory video.

So, based on what we are seeing, can we deduce at what angle the accretion disc is to us?
 

BillTre

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xkcd has an interesting take on the M87 black hole:
241696
 

robphy

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Here is Katie Bouman's TED talk "How to take a picture of a black hole"

while she was finishing her PhD at MIT in 2017.

She's been a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics
and will be an Assistant Professor at Caltech in Fall 2019.
https://people.csail.mit.edu/klbouman/

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

https://www.sciencealert.com/this-29-year-old-computer-scientist-helped-bring-us-the-first-image-of-a-black-hole
 
What does the picture of the black hole actually imply?

I had some begruding idea that this may be sensationaism. Maybe the picture is just too cool for everyone. Is this the reason that it's just blown up everywhere?
 

Orodruin

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Here is Katie Bouman's TED talk "How to take a picture of a black hole"

while she was finishing her PhD at MIT in 2017.

She's been a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics
and will be an Assistant Professor at Caltech in Fall 2019.
https://people.csail.mit.edu/klbouman/
I remember watching that TED talk a couple of years back! :smile:
 

anorlunda

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And this article on the Comp Sci grad student who helped construct the image from the noisy data:
I agree. I've seen her speak. She is a very impressive young woman.
 

sophiecentaur

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There are no 'warning' messages in the press about the fact that the Radio telescope images are not optical images. For interferometry, they have to use phase sensitive detection, which is hard to achieve for optical frequencies over a big area telescope. However, resolution is potentially higher for short wavelengths and there is a factor of about 106 between optical and microwave wavelengths. So it is not beyond the realms of possibility to use a smaller optical telescope array with the same resolution. The actual area of microwave dishes is not in proportion to the aperture width so the signal level would not scale as badly as it might seem.
All we need is optical amplifiers with sufficiently low noise performance (and a few other improvements) and then we could actually 'see' the black holes.
 

davenn

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There are no 'warning' messages in the press about the fact that the Radio telescope images are not optical images.

Yes, True, and this has annoyed me a lot because (as I commented much earlier in this thread) it is making people think that are looking at an optical image of a black hole .... and this misunderstanding is widespread across the net
 

sophiecentaur

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Yes, True,
However - and I felt a bit bad about my comment. I forgot to mention it was a fantastic bit of radiophotography. The other signs of the presence of a black hole (orbiting stars and lensing) are not really as 'obvious' as a real shadow.
10/10 for the project, I say. The quantity of data involved in the processing was pretty stunning.
 

Janus

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Indeed. An excellent explanatory video.

So, based on what we are seeing, can we deduce at what angle the accretion disc is to us?
It's been estimated that the polar axis of the BH is ~17 degrees to the line of sight.
 
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Yes, True, and this has annoyed me a lot because (as I commented much earlier in this thread) it is making people think that are looking at an optical image of a black hole .... and this misunderstanding is widespread across the net
A lot of people, probably most people, think most images they see from space are actually what their eyes would see.
 

DaveC426913

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It's been estimated that the polar axis of the BH is ~17 degrees to the line of sight.
Ah. So we're looking down/up its pole.

That is so damned cool.
 

davenn

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A lot of people, probably most people, think most images they see from space are actually what their eyes would see.

Yes, even with optical images, that is true. I spend a lot of time talking to people about buying a telescope and explaining that what they see in the nice pic's is not what they will see through the eyepiece.
The come to understand that with a good home scope and camera, they can produce images like the ones they see online etc but it takes some serious effort with gear, exposures and processing


Dave
 

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