4 ms·

Should have clarified. Does a black hole have fuzzy edges or sharp edges?

dekhn 5y ago
this is sort of getting into the definition of black holes and event horizons. I don't think they really have solid surfaces, I would expect all imaging here to show fuzzy samples.
- hammock 5y ago
  Like, would it be a gradient from dense-to-fuzzy as you move outward from the center, until you reach the event horizon outside of which is nothing?
  - dekhn 5y ago
    I couldn't really say for sure but I think macroscopically (viewed from a low-resolution telescope) it would look fuzzy, but close up, it would look very spiky and dynamic with all sorts of stochastic events happening.
ISL 5y ago
The edge should be quite sharp. Any deformation or movement in the edge will be smoothed extremely quickly, on timescales comparable to the light-crossing time of the object -- in this case ten seconds or so. If you're a photon and you're in, you stay in. If you're out and heading out, you get out. (if you skim the surface, you might make an orbit and then leave :) ). It is that fact that makes the edge quite sharp.
- sandworm101 5y ago
  I disagree. The edge of a BH is essentially an asymptote. While there is a mathematical bright line, when looking at it you should see light in all manner of red/blue-shifted colors near the event horizon. Since that light is coming in from a variety of directions it leaves in a variety of directions too. Everything would look soft and fuzzy around the edges. Out of focus.
  - codethief 5y ago
    Out of focus? I don't know about you but I find the black hole "edge" in the simulated images in Interstellar quite sharp. (Or are you talking about resolving matter/light near the event horizon? In that case I agree – one won't really resolve any structures anymore due to light getting bent and redshifted in a myriad of ways.)
- codethief 5y ago
  An observer at infinity won't see anything cross the horizon, though, by the very definition of what a horizon is.
  - SiempreViernes 5y ago
    The light crossing time refers to the time needed to traverse a diameter of distance.
    - codethief 5y ago
      Sorry, I misread.
gilbetron 5y ago
Does the sun have fuzzy or sharp edges?
- wolfram74 5y ago
  In case you weren't being rhetorical, the sun's edge would either be the chromosphere[0] or the corona[1], the corona being famously fuzzy and also quite bafflingly hot. The chromosphere is "smoother", but still very interesting on any given day [2]. [0] https://en.wikipedia.org/wiki/Chromosphere https://en.wikipedia.org/wiki/Chromosphere [1] https://en.wikipedia.org/wiki/Stellar_corona https://en.wikipedia.org/wiki/Stellar_corona [2] https://sdo.gsfc.nasa.gov/data/ https://sdo.gsfc.nasa.gov/data/
codethief 5y ago
What do you mean by "edge"? The event horizon?
r00tanon 5y ago
Very sharp. Enough for quantum effects on the edge to produce Hawking radiation.

this is sort of getting into the definition of black holes and event horizons. I don't think they really have solid surfaces, I would expect all imaging here to show fuzzy samples.

hammock 5y ago
Like, would it be a gradient from dense-to-fuzzy as you move outward from the center, until you reach the event horizon outside of which is nothing?
- dekhn 5y ago
  I couldn't really say for sure but I think macroscopically (viewed from a low-resolution telescope) it would look fuzzy, but close up, it would look very spiky and dynamic with all sorts of stochastic events happening.

ISL 5y ago

The edge should be quite sharp. Any deformation or movement in the edge will be smoothed extremely quickly, on timescales comparable to the light-crossing time of the object -- in this case ten seconds or so. If you're a photon and you're in, you stay in. If you're out and heading out, you get out. (if you skim the surface, you might make an orbit and then leave :) ). It is that fact that makes the edge quite sharp.

sandworm101 5y ago
I disagree. The edge of a BH is essentially an asymptote. While there is a mathematical bright line, when looking at it you should see light in all manner of red/blue-shifted colors near the event horizon. Since that light is coming in from a variety of directions it leaves in a variety of directions too. Everything would look soft and fuzzy around the edges. Out of focus.
- codethief 5y ago
  Out of focus? I don't know about you but I find the black hole "edge" in the simulated images in Interstellar quite sharp. (Or are you talking about resolving matter/light near the event horizon? In that case I agree – one won't really resolve any structures anymore due to light getting bent and redshifted in a myriad of ways.)
codethief 5y ago
An observer at infinity won't see anything cross the horizon, though, by the very definition of what a horizon is.
- SiempreViernes 5y ago
  The light crossing time refers to the time needed to traverse a diameter of distance.
  - codethief 5y ago
    Sorry, I misread.

gilbetron 5y ago

Does the sun have fuzzy or sharp edges?

wolfram74 5y ago
In case you weren't being rhetorical, the sun's edge would either be the chromosphere[0] or the corona[1], the corona being famously fuzzy and also quite bafflingly hot. The chromosphere is "smoother", but still very interesting on any given day [2]. [0] https://en.wikipedia.org/wiki/Chromosphere https://en.wikipedia.org/wiki/Chromosphere [1] https://en.wikipedia.org/wiki/Stellar_corona https://en.wikipedia.org/wiki/Stellar_corona [2] https://sdo.gsfc.nasa.gov/data/ https://sdo.gsfc.nasa.gov/data/

codethief 5y ago

What do you mean by "edge"? The event horizon?

r00tanon 5y ago

Very sharp. Enough for quantum effects on the edge to produce Hawking radiation.