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Space is vast,
yet, collisions are commonplace.

Gas and dust electrostatically
flock together.

Gravity takes over
coalescing grains into rocks,

rocks into boulders; then, asteroids

colliding again and again,

striking planets and each other.

Stars collide creating
monsters of light and energy.

Even galaxies collide
over millions of years.

Space is a rough place to be.

That peaceful night's sky
cloaks a hidden danger.

It might appear bejeweled,
docile, and permanent,

but if you look closely, you
can see things happening;

violent things.

Stars engulfing planets and each other,

protoplanets colliding,

explosions rippling through gas clouds,

triggering the birth of young stars,

black holes devouring
everything in their path.

Closer to home, a more immediate danger

is the debris from the
creation of our solar system,

spinning about in a heliocentric orbit

just waiting to bang into something,

something like Earth.

Collision avoidance is
the name of the game,

and we now have the technology
to do something about it.

- Catalina Sky Survey
and other survey programs

are really sort of the start

of the whole planetary
protection ecosystem.

If it starts with discovery,

goes onto follow-up and characterization,

impact risk analysis, mitigation studies,

but you can't follow-up
and you can't characterize

and you can't calculate the impact risk

of something you don't discover.

In order to find a near-Earth asteroid,

we take four images of a patch of sky

separated by about five minutes.

- And we take those four images

and we blink them really fast,

and it creates this little animation

so we can see that the
stars in the background

are a astatic, as they should be,

and if there's anything
that's moving, it'll pop out.

Then, our software
compares those images

and identifies things that are not moving,

which are stars, and removes those,

identifies things that are
transient from frame to frame

and tries to link those up.

- We've probably seen
about a million asteroids

in the last seven years that

the Pan-STARRS has been operating.

It's like picking a
needle out of a haystack.

We're looking for distinctive motion,

and when we see distinctive
motion in asteroids,

we report them to the Minor Planet Center.

The Minor Planet Center is the sort of

world clearing house for
near-Earth asteroids.

- The Center for NEO Studies
takes the observations

from the Minor Planet Center

and computes the high-precision orbits

that we use to make predictions.

CNEOS is also kind of
an early warning system

for newly discovered asteroids.

We take the early data and we compute

whether or not that asteroid
could hit the Earth.

If there's a chance, we'll
send out an early warning

and alert for follow-up observation,

so that we can get more data and then,

we would know perhaps whether
it can hit the Earth or not.

- Asteroid impacts are a fact of life.

The Earth has been impacted by asteroids

continually through its history.

- We saw in 2013 in Russia a fairly small,

by the standards of what we're finding,

asteroid did hit the Earth.

I feel little bit like a
guardian of the planet.

I'm doing my bit to try to protect people.

It is a long-term process.

It's gonna take many, many years to find

all of the dangerous asteroids.

The goal is to

find near-Earth asteroids
before they find us.

Having the right tools

helps us look further
away in greater detail.

The Hubble Space Telescope
was one such tool

that was able to capture
the first spectacular impact

seen in our solar system;

the Shoemaker-Levy 9 cometary fragments,

which struck Jupiter, leaving
a surprising impression.

Even more remarkable
was the recent arrival

of an interstellar object.

- It was a special day when this object

was first discovered.

We have been waiting for the discovery

of an interstellar object
for decades, basically.

Well, when I first heard about

this interstellar object
it was very exciting,

just from a scientific point of view,

that, finally, there's
been an actual observation

of such an object.

- This object is simply a
piece of another solar system

that was expelled and it has been

traveling through interstellar space for

hundreds of millions of years,

billions of years, we don't know.

- A number of our survey projects

and other observatories immediately

turned their telescopes to take
observations of this object.

From the observations we have so far,

it looks like it's a
very elongated object,

maybe about a quarter mile in length.

- We think this object,
2017 U1, is very long.

Perhaps 400 meters or so
long, and very narrow, skinny,

perhaps maybe 40 meters or
so in the other dimensions.

That's a very unusual shape.

We don't see that in our solar system.

None of the asteroids in our
solar system look like that,

so it's very puzzling how it
could have obtained this shape.

- We also see that it's
very reddish in color,

which indicates that it's been

possibly in space a long time

and irradiated by, not only
the light from our sun,

but other suns, as well.

- Well, there's still quite a bit to learn

about this interstellar object
and limited time because

it's on its way out of the solar system.

- It's fading very fast.

It's a relatively small
object so it's very dim,

but we are continuing to
try to use NASA assets,

like the Hubble Space
Telescope and Spitzer,

to take observations to determine more

about its size and composition.

- NASA's Planetary Defense
Coordination Office

has a Near-Earth Object
Observations Program,

which funds efforts that survey the skies

to look for near-Earth asteroids

and to calculate their
orbits and their trajectories

and to determine if any of them

might pose a hazard to Earth,
and as part of doing that,

some amazing discoveries can happen,

and the discovery of
this interstellar object

was one of them.

- As our observational
capabilities improve,

Pan-STARRS has been getting better,

other surveys have been getting better.

There are new generation
surveys that will come online.

We will be detecting more
of these in the future.

New observatories
are being constructed.

To be launched in the coming year,

the James Webb Telescope will orbit

at Earth's L2 Lagrange Point;

1.5 million miles from
Earth, away from the sun.

It's low temperature sensors
will be shielded from

the sun, Earth, and moon.

There're also three new
ground-based observatories underway.

A multi-national project
being built in Hawaii,

the Thirty Meter Telescope, or TMT,

will use 492 hexagonal elements,
each about 1.44 meters,

to construct the single primary mirror

of 30 meters diameter.

The secondary mirror will
be 3.1 meters in diameter.

The largest of all will be Europe's

Extremely Large Telescope, or ELT.

The primary mirror
consists of 798 segments,

each 1.4 meters wide but
only 50 millimeters thick,

with a light-collecting
area of 978 square meters.

The optical design calls for
an immense secondary mirror,

four meters in diameter,

bigger than the primary mirrors of any of

ESO's telescopes at La Silla.

Then, there is the
Giant Magellan Telescope

currently under construction
in the Chilean Andes,

which will be ready by 2022.

It consists of seven 8.4
meter diameter mirrors,

making a total effective
aperture of 24.5 meters.

Housed in a rotating
22-story high building,

it will produce images 10
times sharper than Hubble

with a total collection
area of 368 square meters.

- This is a project that we began in 2003.

It was a small group of U.S. institutions

and has now grown to an
international project

that includes Australia, Korea, Chile,

and, most recently, Brazil.

The next steps, as we launch
construction of this telescope,

are to build the mount, the steel mount,

that will hold the
mirrors for the telescope,

to build the enclosure,
which is a 22-story building,

that has to rotate to allow you

to move to different parts of the sky

as you're looking out with the telescope.

It's a new epic
in the field of astronomy.

It's a new epic for
cosmology, astrophysics,

and the history of the universe.

And so we'll be able to see
things further and fainter

than anyone has ever seen before.

It just takes
us to that next level of

technical capability and
these technical leaps

are what enable new discoveries.

The first four
giant mirrors for Magellan

have been manufactured,
number five is underway,

as is construction at the
site in the Chilean Andes.

- GMT is really an exciting thing

because we know that
over the last 400 years

that telescopes have gotten bigger

and that has allowed us to see things

with better detail and
to see fainter things

and to figure out what the
history of the universe has been.

Our technology for doing this
is getting better and better.

We're able to build big mirrors
and we know how to do this;

we know how to build GMT.

We know to build its individual mirrors

and put them together.

We know that when you
build a telescope view,

and the GMT will have a view

that is 10 times sharper than
the Hubble Space Telescope,

and when you build a telescope
that collects more light,

and the GMT will collect
100 times as much light

as the Hubble Space Telescope does,

that you are going to be
able to do things that

we can imagine and set out as our goals

to look at the history of the universe,

how things have changed,

find out more about the dark
energy and the dark matter.

Those are things that we know you can do,

but I think the really exciting things

will be things that we
haven't yet thought of,

that the new questions that will come.

The other part that's really interesting

about a big telescope on the ground

is that you can change it;

that is you can change the instrument,

so I think that even when
we build the telescope,

that won't be its final form.

Those instruments will
eventually be replaced

by better ones that use the technology

that's developed over the
period from now to then.

We know that the universe has changed

from a very homogeneous, kind of,

goo, at the time of the big bang,

into a highly differentiated world

where there are planets, stars,

galaxies, clusters of galaxies.

The universe has gotten kind
of interesting and complicated

through the action of gravity over time.

We'd like to see how that works

and by looking at what happened long ago,

which means looking at very
distant, very faint galaxies,

and looking in detail, which
means having the resolution

to kind of really see what's going on.

No doubt revealing

cosmic collisions far
back in time and space.

Not as close as the asteroid field,

but still in our neighborhood,

are other phenomena colliding in space.

Out beyond the edge of our galaxy,

the Milky Way is a cloud of hydrogen gas

called Smith's Cloud after its
1963 discoverer, Gail Smith.

It is traveling at 312
kilometers per second

and is about to collide into
the Perseus Arm of our galaxy;

well, in 27 million years or so.

It was believed to have been ejected

from the Milky Way some
70 million years ago.

Why, is still not known but,

when it collides with the galactic arm,

it will trigger a brilliant
burst of star formation

with enough gas to produce
over two million stars.

Another major event to occur soon

is in the heart of our galaxy,

where a super-massive black hole resides.

This black hole's mass is a hefty

four million times that of the sun.

ESO telescopes have been
tracking the motion of stars

around the giant black hole for 20 years.

Although huge, it is currently supplied

with little material and
is not shining brightly,

but that is about to change.

Recently, they have
discovered a cloud of gas

traveling towards the gravity sync hole

on a collision course.

- The cloud consists
mainly of hydrogen gas,

gas which we see anyhow
in the galactic center

all over the place.

This particular cloud weighs more or less

three times the mass of Earth,

so it's a rather small and tiny blob only,

but it glows very brightly
in the light of the stars

which are surrounding the cloud.

- We really don't know
where the cloud came from,

but we do know that most of the material,

which is currently flowing into

the galactic center black
hole, comes from stellar winds,

material which ejected by nearby stars

and it could be that this particular cloud

also was coming from a
star ejecting material

but happened to produce a very compact

and directed it right at the black hole.

Well, the next few years
will be really fantastic

and exciting because we
are probing the territory.

Here, this cloud comes in, gets disrupted,

but now it will begin to
interact with the hot gas

right around the black hole.

We have never seen this before.

We expect it gets hotter.

It may even start emitting
x-rays, very hot radiation,

and then it gets disrupted,
and then, in the end,

we expect it to fall into the black hole,

once it's sort of going
through all of this churning.

As the astronomers watched,

the cloud has been picking up pace

as it gets closer to the giant black hole.

It's speed has doubled
in the last seven years

and it is now speeding
towards the black hole

at more than eight million
kilometers an hour.

The astronomers have already seen

the cloud's outer layers
becoming more and more disrupted

over the last few years as
it approaches the black hole.

- The black hole, imagine it sitting here,

has a tremendous gravitational force.

And the cloud, as it comes in,

it will be elongated and stretched.

It will become,
essentially, like spaghetti.

It will be elongated and
falling into the black hole.

Observations
of other massive black holes

at the center of galaxies have revealed

many varied phenomena.

One galaxy's super-massive black hole

is emitting a powerful
outflow of material.

And, to the surprise of
astronomers, is forming stars.

Results from ESO's very large telescope

are the first confirmed observations

of stars forming in this
kind of extreme environment.

The discovery has many consequences

for understanding galaxy
properties and evolution.

Black holes at the centers of galaxies

still hold many secrets.

Galaxies are the building
blocks of the universe.

The giant galaxies we
see today, even our own,

were built-up from many smaller galaxies

and construction isn't over.

Today, full-grown galaxies approach

and interact with each other.

They may collide and eventually merge,

growing larger and more influential.

As the galaxies approach each other,

the tug of gravity creates
tides that distort their shapes,

stars and gas stream into new orbits.

Sometimes they're completely ejected,

trailing into the depths
of intergalactic space.

Clouds of gas are compressed in the chaos

and ignite with intense
runs of new star formation.

Computer simulations have been conducted

and compared to actual images
of galactic collisions,

an uncanny resemblance.

Because stars create most
of the chemical elements,

each galaxy has a
particular chemical makeup.

This makes identifying groups of stars

from different galaxies easier.

This infrared image of our sky

shows our point of view of the Milky Way,

half a billion stars.

Most are in our galaxy,

some belong to companion galaxies
that orbit our Milky Way,

and some are in between.

Astronomers have discovered
that some groups of stars

belong to a different galaxy,

called the Sagittarius Dwarf Elliptical,

and the Milky Way is cannibalizing it.

As the dwarf galaxy passes
through the Milky Way's disk,

gravitational tides
stretch the dwarf stars

into long streams that wrap
around the galaxy's orbit.

For the dwarf, it's a fatal attraction.

For the Milky Way, just
another one of several

similar events in its history.

But something much
bigger is headed our way;

M31, the Andromeda Galaxy.

This is the Milky Way's biggest neighbor

of roughly the same size mass and type,

and it is speeding towards us.

Astronomers say the crash will begin

in about two billion years.

Super computer simulation
shows how the event

may unfold over billions of years.

The first pass distorts
the two great spirals,

stars are tossed into the intergalactic

night-like sparks thrown from a campfire,

and our sun, complete with planets in tow,

could be similarly ejected.

Gravity will eventually merge
Andromeda and the Milky Way

into a bigger single entity.

With a new generation of
telescopes looking skyward,

we are sure to discover more
dangers lurking in the heavens,

though fortunately for us,

we are millions or billions of years

in time and distance away.