Sagittarius A* and its event horizon

[EinsteinKreuz]

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).

 

[Drakkith]

I haven't heard anything on this personally. I'll have to look into it a bit.

 

[EpicAll Rounder]

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.

 

[stevebd1]

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

 

[Drakkith]

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)

 

[EinsteinKreuz]

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.