Black Holes part 4

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Message 1984719 - Posted: 12 Mar 2019, 11:21:28 UTC

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Message 1984720 - Posted: 12 Mar 2019, 11:32:04 UTC - in response to Message 1984719.  

Nice.
I get dizzy looking at it though:)
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Message 1988341 - Posted: 1 Apr 2019, 19:05:35 UTC
Last modified: 1 Apr 2019, 19:05:46 UTC

According to La Repubblica newspaper the European Commission, the European Southern Observatory, the National Science Foundation, the ALMA array and the Chinese Academy of Science shoul make an announcement on black holes on April 10. But today is April 1 and this looks like an April jest.
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Message 1988392 - Posted: 2 Apr 2019, 4:17:13 UTC - in response to Message 1988341.  

Below is a link to the announcement from the European Southern Observatory's own website. I very much doubt that they would be playing 'April Fools' . It seems that the Event Horizon Telescope, a network of millimeter range radio telescopes throughout the world, may have finally managed to make an image of the event horizon surrounding Sagittarius A*, the supermassive black hole at the core of our galaxy. In any case, we'll hear about whatever it is they've discovered, a week from this coming Wednesday.

https://www.eso.org/public/announcements/ann19018/
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Message 1988402 - Posted: 2 Apr 2019, 5:58:37 UTC - in response to Message 1988392.  
Last modified: 2 Apr 2019, 6:00:06 UTC

Thanks Michael. I would be surprised if la Repubblica published only a joke. The amount of international cooperation is surprising, especially because it includes the Academia Sinica. American scientists are forbidden to cooperate with Chinese scientists. The Italian Space Agency cooperates with the Chinese Space Agency and a module of the Tiangong-3 space station will be built in Torino by Alenia Thales Space. Italian astronauts will be welcome aboard and Samantha Cristoforetti is already studying Chinese after her mission to the ISS on a Russian launcher.
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Message 1988644 - Posted: 3 Apr 2019, 23:32:50 UTC - in response to Message 1988402.  

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Message 1988655 - Posted: 4 Apr 2019, 0:38:19 UTC

Yes, perhaps they'll have an explanation for the odd discovery of an astrophysical jet from Sagittarius A*, which seemed to be pointing almost directly at Earth. This was announced in January, after the ALMA telescope began working with the Event Horizon Telescope system.

Normally, such black hole jets align themselves with the spin axes of their host galaxies. Why the one in our galaxy should point at right angles to this otherwise consistent pattern is not at all clear.
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Message 1989462 - Posted: 10 Apr 2019, 13:19:05 UTC

Will we see the first picture of a black hole today? The researchers behind the Event Horizon telescope have promised "groundbreaking" results on a press conference.
"I don't think anyone will be disappointed," says Robert Cumming at the Onsala Observatory.
Here is one live link from the press conference.
https://www.svt.se/nyheter/lokalt/vast/stor-forvantan-pa-bild-av-svart-hal
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Message 1989463 - Posted: 10 Apr 2019, 13:19:10 UTC

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Message 1989471 - Posted: 10 Apr 2019, 13:57:54 UTC
Last modified: 10 Apr 2019, 13:59:20 UTC

I am still watching the conference at the National Science Foundation. All I can say that all Einstein's predictions have been verified. I published articles by Peter Bergmann and Remo Ruffini on the Mondadori Yearbooks of Science andTechmology in the Seventies. Then black holes were just a mathematical curiosity, then an article by Stephen Hawking and Roger Penrose transformed them into physical objects. Today I have seen one.
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Message 1989475 - Posted: 10 Apr 2019, 14:06:30 UTC

During the press conference, the researchers got the question of what they discovered went against Albert Einstein's theory of relativity.
On the contrary, it is believed that Event Horizon's discovery supports the theory of 1915.
Although Einstein himself was skeptical of whether black holes existed, he was the one who proposed their existence in the theory of relativity.
And got help with the math from Karl Schwarzschild, who found the exact solution only one month later.
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Message 1989501 - Posted: 10 Apr 2019, 15:25:49 UTC
Last modified: 10 Apr 2019, 15:27:12 UTC

I was surprised to find that the black hole was not Sag A, as expected, but M87, much farther. But La Repubblica says that Sag A presented too much dust and observations vere difficult, especially in the millimeter range, used in ALMA. Data collecting went on for only 10 days, data processing took two years at MIT Haystack and Max Planck Radioastronomy Institute in Germany.
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Message 1989509 - Posted: 10 Apr 2019, 15:49:54 UTC - in response to Message 1989475.  

And got help with the math from Karl Schwarzschild, who found the exact solution only one month later.


... while fighting in World War I on the Russian Front, and dying of a rare disease. Quite the accomplishment of determination to do world-class mathematics under such circumstances.
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Message 1989524 - Posted: 10 Apr 2019, 17:11:02 UTC - in response to Message 1989501.  

But La Repubblica says that Sag A presented too much dust and observations vere difficult, especially in the millimeter range, used in ALMA.
I think it's because M87 is an elliptical galaxy so there is not much stuff in front of the center like our Milky Way that is shaped like a disc and since we live quite far from the center there are lot of stuff that hiding the center from us.
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Message 1989544 - Posted: 10 Apr 2019, 21:24:31 UTC

I watched the hour-long press briefing. The astronomers said that they also took data for our galaxy's black hole, are still analyzing it, and hoped to release a comparable image of it soon. This should prove interesting. It might shed some light on the supposed astrophysical jet from 'our' black hole, which seemed to be pointing at Earth, rather than upward and downward through the galactic plane, as expected.
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Message 1989601 - Posted: 11 Apr 2019, 4:55:17 UTC

I watched the hour long program on the science channel and most of the hour consisted of stuff they have already covered. But the images they showed on Wednesday were impressive looking very much like what artists had created when guessing at what the event horizon would look like. Hopefully no one will think that the real images are faked.
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Message 1989603 - Posted: 11 Apr 2019, 5:32:33 UTC

There is an asymmetry in the image. Why is the lower part more brilliant that the upper part?
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Message 1989649 - Posted: 11 Apr 2019, 14:17:02 UTC - in response to Message 1989603.  

Scientists believe it's because that a jet can produce the asymmetry and also that gravitational lensing distort the image.
https://gizmodo.com/what-we-learned-from-the-first-black-hole-image-1833946160
Past observations of galaxy M87 demonstrate that it’s launching a high-energy jet of matter from its center, and physicists have hypothesized that the jet could be powered by energy associated with the black hole spinning. The asymmetry in the glow provides evidence that the black hole is indeed spinning, which could be powering the jet. The rest of the shape would be due to gravitational lensing—the black hole warping light from the stuff behind it, according to the paper published in The Astrophysical Journal Letters.
But they haven’t actually observed the jet yet, Kazunori Akiyama, postdoctoral fellow at the MIT Haystack Observatory leading the EHT imaging group, explained to Gizmodo by phone. And that’s an important area to study, since it could explain how the galaxy M87 evolves more generally—but they don’t yet have the image sensitivity to see the jet itself, nor the jet-forming region.
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Message 1989655 - Posted: 11 Apr 2019, 14:47:31 UTC

Suppose it to be spinnng around a horizontal axis. Then photons coming towards us should have a blue shift, those going away from us a red shift, their speed being the same. Could this explain the change in luminosity?
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Message 1989662 - Posted: 11 Apr 2019, 15:39:18 UTC - in response to Message 1989655.  

Wait a minute. All photons captured on the image are coming towards us with the speed of light and those going away from us are of course invisible. And luminosity is basically only a measure of how many photons you observe, a density of photons.
And as far as I know the only way that the wavelength can be shifted when they travel is when space itself either expand or contract.
So what's left is that the distribution of the photons around the black hole are not even and maybe it's because of some effect that the jet produce. But the jet is not observed yet.

btw. A funny effect being close to the event horizon is that photons are spinning around it.
So when you look to the left when approaching it, you will see the back of your head:)
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Message boards : Science (non-SETI) : Black Holes part 4


 
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