The view from near a black hole
MonstersFromTheId said:
Does anyone know of any artistic renderings of what a black hole would look like to the naked eye, that lean more toward scientific accuracy and less toward dramatic Hollywood glitz?
Ah good, you want astrophysical accuracy--- be careful, since many websites which purport to show visualizations are highly misleading in various ways. Sites from respectable physicists are more likely to be accurate--- or rather, to announce their limiting assumptions up front. I tried to collect some examples here:
http://math.ucr.edu/home/baez/RelWWW/HTML/visual.html
MonstersFromTheId said:
If you were close enough to see (a black hole) with the naked eye, what
would you see?
This rather depends upon whether you have in mind a specific astrophysical object such as the supermassive black hole near the center of our galaxy, or an idealized isolated black hole, with only "distant stars" providing background light. Even the simplest model, the Schwarzschild vacuum (nonrotating isolated hole) provides spectacular effects close up (strong field gravitational lensing), which are sufficiently complicated to explain that you should probably begin with that.
MonstersFromTheId said:
Would you see a "black hole" in the center of the accretion disk?
You'd see a dark disk against whatever background (I'd suggest not worrying about accretion disks at first). This does not represent the horizon but the locus r=3m sometimes called the "photon sphere", because this is the location of unstable circular photon orbits. Just around this dark disk you'd see amplified and smeared images of background galaxies and stars and around that some concentric rings of n-ary, (n-1)-ary, .. 2-ary images of stars whose primary images are seen somewhere else on your celestial sphere.
MonstersFromTheId said:
Or would any view of the black hole itself be completely obscured by light emitted by matter near the black hole as it's torn to shreds by tidal forces?
As I said, the dark disk is the locus r=3m, not r=2m. But you can see glowing matter falling into the hole--- even the "back face" since light rays this close to a hole wind around it several times before escaping to infinity (if indeed they do escape). But you'd see this falling matter rapidly redshift out of visibility at it nears the hole.
MonstersFromTheId said:
Would intense gravitational lensing distort or color stars in the background?
Light bending is independent of frequency, but light from distant stars would tend to be blueshifted as it falls toward you "from infinity".
At this point, you should ask: how does the picture I sketched change for observers orbiting the hole? For observers who fall into it? The details depend sensitively upon the motion of the observer, but some simple special cases are studied in detail in Andrew Hamilton's website (see the link at the above cited web page).
AFAIK, few serious attempts to render scientifically accurate pictures of realistic black holes have been done; the closest I am aware of is an attempt to visualize how any accretion disk would appear warped and how different parts would appear frequency shifted. But there are so many things to consider (not least: human color vision is quite tricky to model!) that nothing I have seen seems sufficiently careful. But I am suprised that (apparently) no one has commissioned a state-of-the-art IMAX simulation with all the bells and whistles.
