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
hole.
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.
