A black hole is a region of space where the force of gravity is so strong that nothing,

not even light, can escape.

Anything with mass can become a black hole.

Say you weight 150 pounds and I compress you down a size smaller than a quark, then you

would become a black hole. Or take the sun. Compress the sun down to

a radius of 2 miles and the sun collapses and becomes a black hole.

One way to make a black hole is through the death of a star.

If you have a star that is 20 times the mass of the sun or more, then as that star evolves

through its life it's going to explode as a super nova and then what's left after, after

the explosion, is a black hole.

But then there are black holes that are much, much bigger, so a million to a billion times

the mass of the sun.

And those are called supermassive black holes. Not just massive, that's not good enough,

it's got to be supermassive.

And it turns out that every big galaxy has a supermassive black hole at the center.

What my group does is we ask the question, How did these super massive black holes build

up their mass?

We don’t understand that part.

One of the great mysteries here is where do these objects come from?

If we're observing these super massive black holes everywhere, and how do they achieve

these huge masses?

These super massive black holes, they don't suck in material. That's a very common misconception.

If you see a black hole, you're not just gonna be sucked straight into it. You are going

to orbit around it just like it's a point mass. For example, if our sun were to become

a black hole, we would keep going around it.

What I first thought about was why can't you just have some galaxy that just has a ton

of gas in it and just feed this black hole to make it into this billion solar mass black


But those kinds of processes of just directly feeding it, that's not enough material to

make it grow to what we observe.

So we specifically as a group study super massive black holes that are often undergoing

some sort of large merger between galaxies.

And we think that maybe super massive black holes merging together is one of the contributing

factors that could explain why they’re so big in the current universe.

So we look for what we call a pair of quasars.

So a quasar is a supermassive black hole with this big accretion disk of swirling gas and

is really, really bright. So a quasar is like a black hole that you can… see.

The biggest paradox about black holes is that they're the blackest things in the universe

but they're also some of the brightest things in the universe.

And that's because when you have a black hole and some gas is being gravitationally pulled

towards it, the gas doesn't just fall straight in. Just like if you fill up your bathtub

with water and you pull the plug the water doesn't just fall straight down the drain.

It kind of swirls around and then goes in. So the same thing happens with gas around

a black hole. Gas is pulled in gravitationally, it swirls around and it forms this thing called

an accretion disc, it's just a disk of gas kind of waiting its turn to fall into the

black hole. But the black hole is so much mass, you're

so close to it, that gas is swirling really fast, it gets heated up and emits lots and

lots of light. So that accretion disk can create more light

than all the stars in the galaxy combined.

Say you have two Galaxies each with it’s own super massive black hole at the center.

When these two galaxies merge together, the two super massive black holes come together

and form a black hole pair.

The black hole pair then merges together to become one more massive black hole.

The galaxy merger itself also creates a huge disturbance in the stars and gas in those

merging galaxies.

It's like a train wreck of disturbed gas with a lot of the gas being funneled toward the

center of the galaxy and feeding the super massive black hole at the center

What we're trying to do is learn about how much galaxy merger can change the way black

holes and galaxies evolve together.

It is fascinating to imagine that something the size of a grain of rice or a penny, that

would be a super massive black hole, could have an impact on something as big as the

Earth (that would be the galaxy).

The way that black holes evolve is tightly connected to the way that galaxies evolve.

If I was plotting the mass of the galaxy against the mass of the black hole, you’d find that

this is a tight line with the mass of the black hole increasing in step with the gas

of the galaxy. So to understand how galaxies evolve, you

have to understand how black holes evolve.

I think we're unique as a species because we pay to build telescopes, to understand

these big questions of our origins and where we came from.

Do you think like a monkey would give up one banana to understand more about where it came

from? No. A monkey would hold on to that banana and say, "You can't take it away from me."

So, you're not going to be able to go out and change anything about the way the universe

is evolving and galaxies colliding, they're not going to impact you on a personal level.

But our lives would change if we could think even on a little bit bigger context, like

a global context and taking care of our planet, for example.

This is just part of pushing ourselves to look a bit bigger.

Bigger than just what's right in front of our noses.