(February 10, 2019 at 11:32 pm)Anomalocaris Wrote:(February 10, 2019 at 4:18 pm)polymath257 Wrote: OK, I took a closer look at the reasoning for 'black stars'. As far as I can see, the distinction between them and 'true' black holes is that they do not have singularities or event horizons. Instead, they are 'frozen' at what would be the event horizon boundary. This, by the way, is expected to happen in the formation of a black hole because of observer effects concerning time dilation near an event horizon.
Again, truthfully, the difference seems minimal. We expect BHs to form via collapse and thereby be subject to the observer effect. From the view of a distant observer, they will *look* like a black star. Since, from the view of a distant observer, there will *always* be matter outside of the event horizon and since the infall takes an infinite amount of time, there is no real difference between a BH and a black star. This is doubly true if the EH and singularity are 'smoothed over' due to quantum effects.
As far as I can see, this is a distinction without an observable difference, which means there is no difference at all.
Time dilation if I am not mistaken only affects free falling towards event horizon. Dark star applies to collapse at less than freefall speeds. Black star in effect suggests that it is possible no true black holes can ever form.
Not true. Time dilation would be significant even if there is no event horizon as long as the gravitational field is large enough. The 'frozen' nature of black stars is precisely this effect.
We expect most black holes to form in situations where there is other matter around. So we expect that there will be matter in a deep gravitational well. It seems that the 'evidence' supporting black stars is that there was a photon signal as well as a gravitational wave signal. But that is expected from BH also because of any extra matter around them.
In essence, a BH with matter around it is exactly the same as a black star from all possible observations. The notions are observationally identical.
This makes a distinction with no difference.
