Sagittarius A* and its event horizon

In summary: So far, some indirect evidence for the redshift has been found, but they still need more data to confirm it.In summary, the conversation discusses a paper from 2009 which concluded that Sgr A* may not be a GR black hole despite evidence of a horizon. However, by 2013, sufficient observational data from VLBI has been collected to confirm the existence of an event horizon and the supermassive black hole status of Sgr A*. There was previous debate and theoretical arguments against black holes, but recent images and data have provided more evidence for their existence. The conversation also mentions a seminar in 2014 that further supports the theory of an event horizon for Sgr A* based on GR. Overall, while we cannot directly
  • #1
EinsteinKreuz
64
1
So in 2009 there was this
paper which described what was known back then based on observational data and the final sentence in the conclusion read as follows:
As a consequence, we cannot yet say that Sgr A* is described by a GR black hole despite being able to conclude that a horizon must exist.

Now for you astrophysicists here, has anything changed? It is my understanding, and please correct me if I'm wrong, that as of 2013, sufficient observational data from VLBI has been collected to show that Sagittarius A* does indeed have an event horizon and finally has been confirmed to be a Supermassive Black Hole. There was considerable debate in the 2000s as to whether or not Black Holes actually exist with plenty of theoretical arguments against them based on Quantum Mechanics(like Jose Pecina-Cruz who argued that they cannot form because this is a violation of the Uncertainty Principle).
 
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  • #2
I haven't heard anything on this personally. I'll have to look into it a bit.
 
  • #3
EinsteinKreuz said:
So in 2009 there was this
paper which described what was known back then based on observational data and the final sentence in the conclusion read as follows:

Now for you astrophysicists here, has anything changed? It is my understanding, and please correct me if I'm wrong, that as of 2013, sufficient observational data from VLBI has been collected to show that Sagittarius A* does indeed have an event horizon and finally has been confirmed to be a Supermassive Black Hole. There was considerable debate in the 2000s as to whether or not Black Holes actually exist with plenty of theoretical arguments against them based on Quantum Mechanics(like Jose Pecina-Cruz who argued that they cannot form because this is a violation of the Uncertainty Principle).
Well, all that is known at the moment is that we have more knowledge of Sgr A* having a event horizon, but not certain. X-Ray and Infrared images have proven that it has a certain "strange pulsing light" after putting a few thousand images into a slideshow. Scientists have also became nearly certain that black holes exist, as again, thousands of images in a slideshow showed material being sucked into a completely black circle. Scientists of course, will not be able to be completely certain that black holes exist until we go to one.
 
  • #4
EinsteinKreuz said:
So in 2009 there was this
paper which described what was known back then based on observational data and the final sentence in the conclusion read as follows:
As a consequence, we cannot yet say that Sgr A* is described by a GR black hole despite being able to conclude that a horizon must exist.
Now for you astrophysicists here, has anything changed? It is my understanding, and please correct me if I'm wrong, that as of 2013, sufficient observational data from VLBI has been collected to show that Sagittarius A* does indeed have an event horizon and finally has been confirmed to be a Supermassive Black Hole. There was considerable debate in the 2000s as to whether or not Black Holes actually exist with plenty of theoretical arguments against them based on Quantum Mechanics(like Jose Pecina-Cruz who argued that they cannot form because this is a violation of the Uncertainty Principle).
There's this slide show/presentation (by the same person who contributed to the paper you linked to) from a seminar in march/April 2014 saying that Sgr A* must have an event horizon (page 23) and providing some background for this theory -

https://www.zarm.uni-bremen.de/sgr2014/pdf/talks/Narayan_WE-Heraeus_Bad_Honnef_Apr_2014.pdf

There's probably other interesting downloads from that seminar-

https://www.zarm.uni-bremen.de/sgr2014/download.html
 
  • #5
We will never "see" an event horizon directly. But, given that GR is the current theory of gravity, we can confidently say that it must have an event horizon if GR (and its solutions) are correct. (unless it's a naked singularity, but I think that's a problematic area in GR anyways)
 
  • #6
Drakkith said:
We will never "see" an event horizon directly.

Correct. But what they are looking for is evidence for infinite gravitational redshifting as well as an image of the Black Hole Shadow cast by its event horizon.
 

1. What is Sagittarius A*?

Sagittarius A* is a supermassive black hole located at the center of our Milky Way galaxy. It has a mass equivalent to about 4 million suns and is about 26,000 light years away from Earth.

2. What is the event horizon of Sagittarius A*?

The event horizon of Sagittarius A* is the point of no return for any matter or light that gets too close to the black hole. It marks the boundary where the gravitational pull of the black hole becomes too strong for anything to escape, including light.

3. How is the event horizon of Sagittarius A* determined?

The event horizon of Sagittarius A* is determined by the Schwarzschild radius, which is a measure of the distance from the center of the black hole where the escape velocity exceeds the speed of light. This radius is estimated to be about 17.6 million kilometers for Sagittarius A*.

4. Can we see the event horizon of Sagittarius A*?

No, the event horizon of Sagittarius A* cannot be directly seen as it is beyond the reach of our telescopes. However, scientists have been able to indirectly observe its effects, such as the bending of light and the movement of stars around the black hole.

5. What can we learn from studying Sagittarius A* and its event horizon?

Studying Sagittarius A* and its event horizon can help us better understand the nature of black holes and the effects of extreme gravity. It can also provide insights into the formation and evolution of galaxies, as supermassive black holes like Sagittarius A* are thought to play a crucial role in shaping their structures.

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