So to really get a sense for these objects nothing is better than an actual
tour luckily a virtual tour to a black hole.
Our tour guide is Andy Hamilton of Colorado University who has generously
let us use these beautiful simulations he's made.
So we're, we're er, going to approach this
Little system of stars we got a 60 solar mass blue main sequence star with some
other e smaller stars and orbiting in a binary system with this blue star is a 30
solar mass black hole, which of course we can't see and
30 solar masses tells us that its Schwarzschild radius is 30 times the sun
mass, three kilometers. And this is an image of our trajectory.
We are going to be in free fall, so we're going to be accelerated towards
the system and fall into an unstable orbit at, two Schwarzschild radii.
That is a zero energy orbit, so you can actually freely fall without
any engine power into that unstable orbit.
You don't want to miss, because if you miss by a little bit,
you either could fly, flown back off to infinity or fall into the black hole.
of course since it's virtual, we'll manage to survive it either way.
But let's start by approaching this system from a distance and see what the
effects are of coming close to a black hole.
So, I start the simulation and we are falling from a 100 million kilometers. As
we approach at about a 100 Schwarzschild radii, the lensing of the black hole
produces what is called an Einstein ring. The hole, a doughnut-shaped image of the
blue star, which is formed by light lensing and bending all around the black
hole. And as we get nearer we see multiple
lensed images of all of the stars, because remember we are now at The, this
clip ends at three Schwarzschild radii, the last stable orbit. deflection of
light is significant and we see these multiple lensing effects.
Notice that on the bottom, on the horizon itself the
animator has superimposed this nice red grid for us. Of course the actual horizon
does not have a red grid on it and if it did you would not be able to see it.
But this just tells you where the Schwarzschild horizon is, and the
interesting property is that because of the deflection of light note that you can
see both poles of the horizon. So you can see all the way around it because light
is so greatly deflected. anA so that was us at the last stable
orbit, at three Schwarzschild radii, but that is for sissies. We are heading down
to two Schwarzschild radius orbit. We are now orbiting the black hole at two
Schwarzschild radii. We see all of the enhanced lensing
effects that I was talking about. We see multiple images of all of the
stars, in the cluster. forming and disappearing.
If you want to know the proper time period of orbit is about four
milliseconds. first to someone viewing us from far
away, it's a factor of two. Note what a two Schwarzschild radii.
The gravitational redshift factor is a square root of two,
but there's another square root of two because we are moving at about 0.7 times
the speed of light to maintain this orbit at two Schwarzschild radii.
You can compute both of those things. So looking from afar, we would appear to
be orbiting at every eight milliseconds, where in fact we think we're orbiting
every 4 milliseconds. The tidal forces at this point are I
believe a thou- a 100 times G. So your feet are pulling on your head
with 100 times their weight. You're getting a little bit uncomfortable, I
should think, and then these white dots are a probe
that is being dropped conveniently, 400 kilometers ahead of us.
down onto the surface of the black hole from rest,
and as we approach it we see it falling down because it's dropped ahead of us in
orbit and we see it falling down. And what we see is A, this probe is a
sphere and we see this tidal force stretching it out till it's no longer
anything like a sphere. And second of all, we see there as it
would fall, as it approaches the Schwarzschild horizon,
it is reddened and slows down. The bit that is closest to the horizon
appears to stop falling first, and eventually, it turns red, and merges
with the horizon. We can't see it because the red shift is
infinite, even between the Schwarzschild horizon and the orbit at two
Schwarzschild radii where we are. And now,
well this is unstable, but not dangerous enough for us.
We're not here for the tourist version. We're going all the way.
We're going to fire the boosters slow ourselves down slightly and land on, well
not land, but penetrate through the surface of the black hole.
We just cross the horizon, and at the point that we cross the horizon within
about a tenth of a millisecond, we are going to be in the, hitting the
singularity for a 30 solar mass black hole.
The g-forces at the Schwarzschild of radii, radius for this 30 solar mass
black hole are a million g. So we have long since been decomposed,
and as we fall through the horizon, we will meet anybody who fell through
just before us, and we have a tenth of a millisecond to
have a deep conversation with them before we hit the singularity and everything
ends. So this was a quick tour of a black hole.
And you lived to tell.