What the Black Hole Picture Means for Researchers

This is the first ever image of an actual black hole.

It's in the center of a galaxy called M87,

55 million light years away.

Until now, all we've had are simulations

and hints and cosmological data,

but now we can actually see something

and it turns out to be actually quite beautiful,

and also sort of terrifying.

So to talk about that we have a couple

of Harvard astrophysicists,

Michael Johnson and Andrew Chael,

who both worked on the project,

and they're gonna talk a little bit

more about what we're seeing.

The famous thing people say about black holes,

the gravitational field is so powerful

that not even light can escape.

Well, of course we're seeing something around it.

Some stuff does come out.

So what actually does come out of a black hole?

And what do we see when we see this orange sort of nimbus?

What can you tell from that?

What are we looking at exactly?

Nothing comes out from inside the event horizon,

which is the boundary that you probably think of

when you're thinking of a black hole.

What we're seeing is actually light

that was captured on a circular orbit

around the black hole and it flung off.

That's at the point where the gravitational field

is so strong that it's making the photons orbit.

If those photons venture a little bit too far

inside the orbit, they'll fall in.

Once it's past the event horizon, nothing,

but there are things sort of at the edge?

Once it crosses the event horizon, the material is gone.

But as stuff's coming in, it's getting

more and more compressed and heated,

and there's viscosity from magnetic fields

that are shearing apart and tearing.

So it's heating everything up

and all of the omission is getting amplified

just before it crosses that event horizon.

All of this material is getting hot,

emitting most of the energy once

it gets close to the black hole,

and at that point the black hole takes over

and is warping it into this distinctive shape.

So not only is it an incredible distance away,

but the image that we're seeing is also,

for all intents and purposes, 50 million years old, right?

We're pretty far behind here in a way.

M87 is a very popular target for astronomers.

All astronomers looking at M87

are looking at the same 50 million year old light.

The big difference for us is that

we just see this massive star, this big ball of light.

And if you look carefully,

you'll see a little jet riding off to the side.

We zoom in on this image that Hubble sees.

Zoom in by another factor of one or 2,000,

and that gets us down

to the very heart of this entire region.

It's all a game about how fine of those details can we see?

And so what did it take to actually see it?

What did you have to do to look that far away?

How far is it?

What kind of telescopes do you use?

So it's about 50 million light years away.

Because of that, it's basically so small

that we can't look at it with a normal telescope.

We basically hitched together telescopes

from all over the world,

the South Pole to Chile to Hawaii to Spain,

and then record the data there visually,

and then go take that data back

and sort of try to reconstruct the underlying data.

But that's not a very forward process

because we're only sampling effectively

a mirror the size of the Earth and a few locations,

and from that dataset, we have to recover the image.

But that's a lot of the challenge of the project.

I know you haven't had a lot of time with it yet,

but looking at it, does it conform to theory?

Is there something that you learned

about black holes that was surprising about it?

Does it say that yes, we still understand physics?

What does the image tell you?

So to me, we've known that there were these

intense concentrations of mass at the centers of galaxies,

but I didn't expect for a moment

that we really would turn on a telescope

and see this ring of light surrounding

a seven billion solar mass black hole.

I mean, I expected some messy, astrophysical jet.

But instead we see this elemental, booming signal.

It's really just jaw dropping.

So in that sense, I do think

it's a confirmation of this theory,

but even in its confirmation,

I find it to be quite surprising.

The signal of the bright range is universal,

that it comes directly from gravity

and you can do a lot of different things

with the astrophysics around the black hole.

You can heat the particles in different ways.

You can make it more or less dense,

but you always get this ring.

So I think a lot of what's coming in the future

will be what signals can we now use

beyond just a ring in the image,

maybe polarization, maybe time variability

to help the image if you look at it

from week to week or year to year.

So you really get at those astrophysical questions.

If it were possible to look at this with the naked eye,

if it were possible to fly a ship closer to it,

what would it be like to be there?

Our images make it look like it's a sleeping giant,

but it's not, right?

This thing is tremendously dynamical.

It's like the surface of the sun.

It's boiling and erupting,

and I think that would just be

a tremendously exciting environment.

M87 is a super massive black hole

with seven billion times as much mass as the sun,

and these are sort of gentle monsters

where you can creep up to the event horizon

and it won't tear you apart

like it would for a stellar-mass black hole.

You can cross that event horizon

and you might not even feel it.

If you wanted to park a spaceship outside the event horizon,

you would feel a lot of gravity from the black hole.

You'd weigh about 200 times as much as you do on the Earth.

But that's not so crazy that you're sitting

outside this incredible black hole,

but at the same time you would see this erupting

ball of fire as in this terrifically dynamical system,

analogous to, say, the surface of the sun.

So it'd be really beautiful to behold.

There's another black hole close to use called Sgr A*.

It's in the center of our own galaxy in the Milky Way.

But just because it's closer

doesn't mean it's easier to see.

Do we get a chance to look at the one

that's at the center of our own galaxy at some point?

Though Sgr A* in the center of our own galaxy

is a much better source even for a lot of reasons,

we have a lot more detailed probes.

We can see individual stars going around it.

We know its mass and distance much more accurately than M87.

The difficulty is a day in the life of M87

is a minute in the life of Sgr A*.

And so we see these hints of variability in M87 over a week,

and that means that for Sgr A*,

we're expecting to see all sorts

of dynamical activity over a minute,

which just makes it a much more difficult problem

to turn that into a single picture.

Michael johnson and Andrew Chael.

Thank you so much for doing this. Really appreciate it.

Congratulations again.

It's an amazing result.