vast, wondrous, electrifyi ng. But for space travelers
looking for a thrill rid it could be a one way ticket. It's a place from which you
can't return, or at least not in the form in
which you went in. NARRATOR: Go where no
one has dared to venture. Take a virtual tour of the
deadliest places in our galaxy and beyond. [theme music] It's the ultimate frontier
adventure, space travel. But when trekking through
the galactic jungles, one must steer clear of
the cosmic hot zones, places teeming with
violence and intrigue. There are dangerous places. Certainly very
energetic phenomena that are a lot more powerful
than atomic bombs being detonated, infinitely
more powerful. The universe does seem
to be a very violent place. It seems to have been born
in a violent explosion called the Big Bang. And there's all sorts of
violent processes going on. NARRATOR: On December
27, 2004, satellites picked up the greatest cosmic
explosion ever recorded. A blast 30,000 light
years away, which had the power to briefly alter
our planet's upper atmosphere. The blast was caused by a
magnetar, the densest and one of the most dangerous
stars in space. The magnetic field
strength of a magnetar is about 1,000 trillion times
the magnetic field energy of the Earth. And for reference, this
would wipe the information off a credit card at a distance
of about 100,000 miles away. Now, this distance is sort of
half the distance to the moon, so it's very nearby by
astronomical standards. NARRATOR: These mischievous
stars have the strongest magnetic field in the universe. Scientists have confirmed 12 of
these rare stars in our galaxy, and there may be more. Caltech's Brian Cameron
scans the Milky Way for these strange stars. Magnetars are a special
class of neutron stars with ultra-strong magnetic fields,
the densest form of matter in the universe. The first magnetar showed itself
in the form of a high energy event that was detected in the
late '70s, although at the time we didn't know that
it was a magnetar. It wasn't until the early '90s
that researchers suggested that these objects were
dominated by magnetic fields, and that the magnetar theory
was actually confirmed. NARRATOR: Magnetars are
born out of the death throes of massive stars. When a star dies, it begins
to collapse and go supernova. Sometimes a dense neutron
star from the cinders of that supernova explosion. During the process,
a few neutron stars become magnetars,
which possess a strong magnetic field. These stars eject high energy
emissions of x-rays and gamma rays. We think that normal
neutron stars are born from regular stars that are
something like 10 or 20 times the mass of the sun,
but there's evidence that magnetars are
born from possibly even more massive stars than
this, something like 40 times the mass of the sun. NARRATOR: Typically,
a star of such mass would be too heavy to
form a neutron star. Instead, its mass would
collapse into a black hole. Black holes are formed from
cramming a certain amount of mass in a certain volume. And for whatever reason, these
stars are unable to do that. NARRATOR: One theory is that
some massive stars undergo a weight loss program
right before exploding as a supernova, losing
90% of their mass. So instead of collapsing
into a black hole, the emaciated star
becomes a neutron star with extreme magnetic powers. When the magnetic force
gets incredibly strong, it deforms the magnetar's crust,
creating seismic events called starquakes on its surface. And eventually this crust
breaks under the stress, and the magnetic field
reconfigures itself into a lower energy state. And when this
happens, a fireball is launched off the
side of the star. So starquakes on
neutron star surfaces are thought to give rise to
these giant flares that we see. After a magnetar undergoes
one of these flares, it outshines all the stars in
the galaxy for the few tenths of a second that
it's taking place. NARRATOR: Within
these giant flares are short bursts of
gamma rays, which move at the speed of light. The giant flares from
magnetars are gamma ray bursts. They're very short in
duration, less than a second, and have very hard X-ray spectra
compared to another class of gamma ray bursts. NARRATOR: If a deep space
traveler veered off course and was unlucky enough to
pass within 700 miles of one of these massive objects, the
consequences would be horrific. The magnetic field
of the magnetar can literally warp the
atoms in human flesh, and its gravitational forces
would tear a person apart. So then how close would a
magnetar have to be to wreak havoc in our solar system? Some suggest that a blast from
a magnetar even 10 light years away could produce cosmic chaos
that would destroy our ozone layer and cause
mass extinctions. The chances of that happening
are so low that they're completely implausible. It would be no different
than a regular star passing through the solar system. And we know that a
regular star has not passed through the solar system
since the solar system formed. NARRATOR: Scientists
think that magnetars are only a few
thousand years old and will become dim
after 10,000 years. We're just now starting
to understand the life cycle of magnetars. We think that
they're very young. But how young is
still uncertain. NARRATOR: In addition
to magnetars, satellites and
ground-based observatories have been picking up other
violent things in space. Scientists have now
confirmed the existence of a phantom-like force that's
so strong that it might very well be the most vicious
phenomenon in the universe. Stealthy villains haunt
each and every galaxy. One particular beast tears
up anything in its path and gobbles it down like
a cocktail hors d'oeuvre. It's one of the most bizarre
and destructive phenomenon in the universe, a black hole. I think a black hole
is the place which is more violent than anywhere
else in our universe. It's like going over the
edge, and you can't get back. It's fatal
attraction, I suppose. NARRATOR: A black hole
is a region of space where the pull of gravity is so
immense that nothing can escape it, not even light. Astrophysicist and
triathlete Feryal Ozel is attempting to unlock
the mysteries surrounding this elusive cosmic force. In a black hole, the
gravity is so strong that no other force
can compete with it, so everything collapses
to a single point. NARRATOR: Ozel says whatever
has a close encounter with a black hole
will fall victim to its relentless
tidal force of gravity. Imagine you're swimming in a
pool and there is no current. You can go whichever
direction you want. Now imagine you're
taken out of this pool and you're in a river. Imagine the current that is
much, much, much stronger, and that the only
direction that you could go would be with this current. The space around the black
hole acts like this wild river. You could never fight this
enormous drag that you feel. NARRATOR: As an object
approaches the edge of the black hole,
called the event horizon, it reaches the
point of no return. As you come closer and
closer to this event horizon, you would already be approaching
this extremely fast motion of space under you, and
your only future direction is now into the black hole. The idea of the black
hole as a hole sometimes can be a little bit confusing. What it really is
in some sense, it's a place from which you can't
return, or at least not in the form in
which you went in. NARRATOR: Black holes
are difficult to detect, because as the name suggests,
you cannot see one by itself, because it's black. But scientists have
spotted a black hole when its gravity affects
something else in space, such as a passing star. A completely isolated black
hole would not be visible. What we really see
from a black hole is actually the hot material
that's swirling around it, and that's being sucked into it. So in the neighborhood of
these powerful black holes, you'll get a lot of radiation
resulting from the black hole pulling in material and
stretching it and twisting it as it's falling in. NARRATOR: Black holes consume
anything in close range. And there are billions
upon billions of them, prowling the universe. Astrophysicist Andrea Ghez
is one of the world's leading black hole hunters. Black holes are
not picky eaters. They'll dine on
whatever get nearby. So they will happily eat gas. They will happily consume
a star or a planet. When a black hole
dines on a star, it does so first by
tearing it apart. Well, you might think of silly
putty being stretched out and then it just streams on in,
sort of like water going down a drain. It's completely pulverized. Black holes are
produced, we believe, by the collapse of the core
of a massive star, something like 25 or 30 times the
mass of the sun or more. When it comes to the
end of its lifetime, the massive star burns its
core all the way past helium, carbon, nitrogen, oxygen,
all the way to iron, which has no more nuclear fuel. And when that iron core
builds up to a certain mass, there comes a point where it
can no longer support itself, and the core will collapse
all the way to a black hole, producing at the same
time a supernova. NARRATOR: The
supernova sends out explosive amounts of energy. so anything in its vicinity
will get obliterated. Then the remnants
of the explosion fall into a newly formed black. And it seems the key to the
black hole's allure is gravity. Gravity will
pull things around, just like the sun's gravity
pulls the planets around. In fact, stars will happily
orbit the black hole for most of its life, and
won't actually be sucked in. These stars are actually safe
from the fatal attraction of the black hole. But if you do venture too close,
extremely close to the edge, then you do get sucked in. NARRATOR: Scientists
believe there are millions of wayward black holes
throughout our galaxy, the Milky Way. And because we can't
readily see them, one could be right next door. So how close does something
have to be to get sucked into a black hole? Too close to a black
hole is about the distance between the Sun and the Earth. But that is certainly too close. NARRATOR: For future
space travelers, death by a black hole would
be a violent way to go. The method by which a
black hole could kill you depends on how big
the black hole is. They come in two categories. Most of them are the
stellar mass black holes, which are 5 to 30 times
the mass of our sun. If a black hole
is stellar sized, then the tidal forces
near the black hole are strong enough that it
will tear you apart tidally even well outside
the event horizon. If you wanted to fall
into a black hole, you certainly wouldn't want
to fall into one of those. It will spaghettify you. NARRATOR: But in addition to
the stellar sized black holes, there are others that are
mammoth, millions to a billion times the mass of the sun. And now scientists believe
that these monsters hold center court in every
galaxy, including our own. Black holes, they're one of the
most mysterious and potentially dangerous oddities in space. A black hole has a
ravenous appetite. It sucks in everything
in its path and spits out what it doesn't devour. And now scientists
have discovered there are supermassive
black holes, which are millions of times bigger
than their stellar mass cousins. And evidence suggests that
supermassive black holes were born after the Big Bang, when
the universe was first created. The leading idea is that
they would have formed just like a stellar black hole,
from the collapse of the core of a massive star. But then they grew by
feeding grossly from the gas, from other galaxies
which collided with them. NARRATOR: Scientists
have discovered that these black ogres
wield their power in the center of galaxies. The supermassive black holes
are at the center of the galaxy most likely because they're
the most massive object within the galaxy. Massive objects tend
to sink to the middle, so you'll always find them
at the center of a galaxy. NARRATOR: For a long
time, scientists didn't think a supermassive
black hole existed in our neck of the universe, the Milky Way. But in 1995,
astrophysicist Andrea Ghez set out to prove one exists. We've done an experiment
over the last 10 years to ask the question, is there
a supermassive black hole at the center of our galaxy? And the way we did
this experiment is to use the motions of stars
at the center of our galaxy to test whether or not
there's a large amount of mass inside a very small volume. And that's the proof
of a black hole. NARRATOR: At the Keck
observatory in Hawaii, which houses one of the largest
telescopes in the world, Ghez began using a
groundbreaking technology called adaptive
optics, which brings into focus far away objects. So this is, without
adaptive optics, this is what you would see. In this big square,
there's nothing. We turn adaptive optics
on, and you see the stars. This region contains the
stars that provide the keys to our experiment. So we want to watch
how these stars move. NARRATOR: Ghez noticed that
there was a large cluster of stars orbiting around an
invisible object at the center of our galaxy. And they were moving at
an unusually rapid rate. So we can actually
see these stars that are really close to
the center, and we can watch them go around. The stars go around
the black hole just the way the
planets orbit the sun. The orbits tell us
where the black hole is. So it's located right
where the star is. That's the center of our galaxy. And the details of exactly
how fast these stars are going around and how
tight the orbits are tells us the mass of
the black hole, which we think today is four million
times the mass of our sun. NARRATOR: For Ghez, confirming
that a supermassive black hole indeed exists at the
heart of our galaxy was like summitting
mount Everest. It was incredibly
exciting to discover the supermassive black hole
at the center of our galaxy, simply because it was a question
we had set out to address. The question "is there a
supermassive black hole?" And we could design an
experiment that actually got at it. NARRATOR: Astrophysicist
Andrew Hamilton says death by a
supermassive black hole would be much different than
by a smaller stellar mass relative. If you want to
go and be a tourist and have the ultimate experience
of falling inside a black hole and finding out what
is really there, go visit a supermassive
black hole. Much better idea. NARRATOR: Unlike a stellar
black hole, which would review to shreds before entering
its deadly vortex, a space explorer could actually
experience free falling inside a supermassive
black hole. Inside of a
supermassive black hole, it turns out that even though
the black hole is more massive, it's also much larger
in size, and that means that the tidal forces are
weak enough that you could pass through the event horizon and
fall deep inside the black hole without being
tidally torn apart. But deep down inside
the black hole, the centrifugal force of the
rotation of the black hole provides effectively
a repulsion. If there's any matter
at all inside it, then stuff that's falling in
will tend to collide with stuff that's trying to get out. And the result of that
collision of energies is an unimaginably
chaotic maelstrom of super hot dense plasma. And in that case, your fate
is that it can roast you. NARRATOR: So how close
would space travelers have to be to get sucked into
a supermassive black hole in the center of a galaxy? For a supermassive
black hole, you would have to be about a
million to a billion miles from the black hole
to feel its influence. NARRATOR: Over the years,
the Chandra X-ray observatory has caught our galaxy's
supermassive black hole nibbling on cosmic
matter, not bingeing like other supermassive
black holes. Our black hole
is today inactive compared to other black holes. Our galaxy has very
little gas at the center. And so there's nothing really
for the black hole to feed on. It's not eating very much. It's going on a bit
of a starvation diet. NARRATOR: Our galaxy's
supermassive black hole appears to be fasting. This is partly due to the
fact that as a galaxy ages, less and less matter is
present for it to gorge on. But in the future, it might
be quite a bit more active, if it ever gets a
fresh supply of gas at its center to feed off of. NARRATOR: One way to rejuvenate
our supermassive black hole's appetite is to collide
with another galaxy. Sound implausible? 2 million light years away, our
closest neighbor, the Andromeda Galaxy, is charging toward us
at almost 75 miles per second, or 270,000 miles per hour. In the future,
scientists predict the two galaxies will collide. And upon impact,
the larger galaxy may engage in one of the
most primitive acts known in the universe. It's one of the most
barbaric rituals in space. A larger galaxy
eats a smaller one. The scenario isn't a science
fiction writer's fantasy. It's a cosmic reality. It's called galactic
cannibalism. The ghastly event can occur
on the celestial highway, when two galaxies have a
head-on collision. Both eventually meld together in
a less than harmonious merger. If you're a galaxy,
it's very violent. You're torn to shreds. NARRATOR: Joshua Barnes
studies galaxy mergers. Acting like a crime
scene investigator, he admits his research is a bit
like inspecting a car crash. Imagine that you come across
the scene of a car crash. Two wrecked vehicles,
but no witnesses. Nobody to tell
you what happened. All you have is the
physical evidence. That's basically what we have
to do when we study colliding galaxies. So there are no witnesses
to a galactic collision. All that you have is the
present state of the wreckage. So you have to conduct a sort
of forensic investigation to try and figure out what
happened on the basis of what you have today. If they collided head-on, you
would know because the fronts were squashed up. But if they, say, sideswiped
each other, which is actually more likely in
galactic collisions, that would leave you a
completely different pattern of wreckage, and you
could interpret that. NARRATOR: So what
causes galaxy mergers? It's gravity. Everything in the universe is
falling freely through space. And where you've got two
large objects like galaxies, their mutual gravity
pulls them together, so they fall into each other. So it's really just the force of
gravity pulling things around. The galaxies that we're seeing
colliding today, most of them have been bound and destined to
collide for upwards of 10, 15 billion years. And they're only now just making
it to that first collision. NARRATOR: Our own
galaxy, the Milky Way, is moving toward our
neighbor Andromeda. Both galaxies are
spiral in shape, but Andromeda is about
twice as massive, with a supermassive black hole
the mass of 30 million suns. It'll look a lot like a dance. And you see the two galaxies
come close together, so they kind of dance around each
other, getting closer and closer and moving faster and
faster, before they finally come together. NARRATOR: But at the point of
impact, these galactic dancers will do more than pirouette. Each one has a
spiral disk of stars, and then surrounding that
a halo of dark matter, invisible material
that we can detect by its gravitational field. These two dark halos,
which are much larger, will overlap as the
galaxies pass by. Eventually, as the two galaxies
spiral around each other closer and closer, you can no
longer distinguish them as separate systems. And finally the nuclei merge. When Andromeda and the
Milky Way collide, that's going to be the biggest
collision that the Milky Way has seen, something
like 5 billion years time. The good news is that
we, the solar system, will have a grandstand view. What will happen is
the two galaxies, their spiral disks are
gonna get tidally torn apart into fantastical shapes. When the disks start to
get close to each other, they'll throw off long
streamers of stars, so-called tidal tails. And what happens to the
sun and the solar system, should we still be around,
it really is hard to predict. We could get lucky and be
on one of those tidal tails and get a sort of bird's eye
view of the whole process as we fly out. Or we could get thrown
into an orbit plunging towards the center of
the merging galaxies. There's basically no way to say. NARRATOR: During the merger,
if our solar system moves through the suburbs, or
the edges of Andromeda, we might not notice anything. On the other hand, countless
stars and space material could be propelled
towards the planets, potentially disrupting
their orbits around the sun. Moreover, the entire galaxy
could face cosmic upheaval. We could have consequences,
which would nonetheless be dangerous. First of all, we could have
a lot of star formation as a consequence of the merger. Currently, both the Milky
Way and Andromeda Galaxy have plenty of interstellar
gas, the raw material from which stars are born. Now, that would mean a lot more
evolved star supernova going off in our vicinity. And that could create
shockwaves, blast waves, bursts of cosmic rays, which
would have nasty consequences. NARRATOR: After the merger,
the fate of our solar system is uncertain, as the
supermassive black holes of Andromeda and the
Milky Way vie for power in the newly jumbled galaxy. When they merge, they're
gonna form a new galaxy, and those two supermassive
black holes will gradually spiral into the middle
of the new galaxy. They will be a binary black
hole for a short time. And these black holes
will start to swallow gas. As the collision
stirs things up, gas will fall into
those black holes. They're going to turn on. They're going to start
emitting radiation. But the potential for
fireworks, possibly for fueling the black holes at
the centers of the galaxies, matter falling into them,
possibilities like that do exist. And then the only safe place
to watch the process would be on one of those tidal tails,
riding out and escaping the collision. NARRATOR: Some scientists
think that Andromeda's larger supermassive black hole will
eventually consume the Milky Way's. The black holes will
spiral in the center, and become a binary black
hole, and ultimately will merge with one another to become yet
an even bigger supermassive black hole. So a small galaxy
colliding with a large galaxy is likely to be dominated
by the larger galaxy. It'll essentially have most of
its material absorbed by that galaxy and become
subsumed into it. NARRATOR: Scientists
believe galaxy mergers are a way of life in the universe. Modern galaxies,
including the Milky Way, have grown larger by
cannibalizing smaller galaxies. Every galaxy that
we see has probably been through many collisions. The Milky Way has
a central bulge of stars, which are probably the
relic of a previous collision. NARRATOR: Most
scientists agree that the much anticipated
merger between the Milky Way and Andromeda won't happen
for at least 3 billion years. But there may be more
immediate dangers in space. In cosmic neighborhoods
millions of light years away, there are hyperactive
galaxies that have become the big bullies on the block. At the heart of some galaxies
lives a cosmic monster. It transforms a run
of the mill galaxy into one of the brightest
and deadliest in space. Quasars are peculiar
objects, each powered by a supermassive black hole
that continually swallows large amounts of matter,
10 to 20 stars every year. At the core of these objects
lives a very large black hole. And the role of that black
hole is to actually generate a huge amount of energy. NARRATOR: Quasars are the most
energy efficient mechanisms in the cosmos. They give off more power
than 100 normal galaxies. And they're 10 trillion
times brighter than our sun. So how are quasars
created in the universe? There's a fairly good
connection between the last stages of a galactic merger
and the so-called quasar phenomenon. If that really happens
in the case of the Milky Way and Andromeda, we could
have for a period of some tens or probably even
100 million years a quasar active from the
center of submerged galaxies. And a quasar puts out about
100 times as much energy as a typical galaxy. And if we were actually thrown
into an orbit which took us towards the center
of the galaxy, we could get very close to that
quasar and really get scorched. NARRATOR: The word "quasar"
stands for "quasi stellar radio source", which means star-like
emitters of radio waves. The word was coined when the
quasar phenomenon was still a mystery. Now we know they're
not star-like at all. In addition to emitting radio
waves and visible light, quasars also give
off ultraviolet rays, infrared waves,
x-rays, and gamma rays, all deadly if something
or someone gets too close. A quasar is the supermassive
black hole at large distance that is active. It's powerful. It's emitting light, and we can
observe it in many wave bands. NARRATOR: Quasars were first
discovered in the 1960s. But as radio telescope
imaging got better, astronomers discovered
that some of those quasars also have powerful jets
beaming out of them. These particular quasars
are called blazars, probably some of the most violent
phenomena in the universe. Blazars are powered by black
holes, just like quasars, but they're somewhat different
in that all of that energy is being focused, or a
large amount of that energy is being focused into jets,
which are streaming out. NARRATOR: A blazar's aggressive
plasma jets produce radiation in the form of radio waves all
the way through the spectrum up to high energy gamma rays. Astrophysicist Glenn Pinter
has been investigating the physical conditions
at the centers of these exotic galaxies. We can use this
fountain to visualize the geometry of a blazar. If that circular
base of the fountain represents the accretion
disk, then the jet of water that's coming up
represents the jet of plasma coming out from the blazar. And if the Earth is
sitting up in the direction that that water is going,
then we would see this object as a blazar. For an astronomer, it's
like looking down a firehose. It really gets you in the eye. You see this bright, blazing
thing that we call a blazar. NARRATOR: These blazar jets
move exceptionally fast. The fastest observed move
at 99.9% the speed of light. If you were to take a small
object like this bowling ball, and you wanted to
do accelerate it up to 99.9% of the
speed of light, you would have to give this bowling
ball all the energy produced in the world for an entire week
to accelerate it to that speed. And in these blazars,
we're accelerating not just small objects like
bowling balls, but large masses of
the mass of the planet Jupiter or larger
to those speeds, so they're being given
incredible amounts of energy by this efficient engine. NARRATOR: Blazars pose
unimaginable consequences to cosmic objects that get
too close to its deadly jet. If there was a planet
relatively close, a few light years from the
actual jet, the radiation on that planet could
be millions of times what it gets from the star. It would be continually exposed
to high levels of radiation. So I don't think we want to look
for life on a planet that would be orbiting a star
that's in a blazar jet. NARRATOR: Scientists link radio
telescopes all over the world to achieve the magnification
needed to zoom in on a blazar jet. So to give you an analogy
for what kind of magnification that is, that would
be magnification sufficient to read a newspaper
that someone was holding in New York from Los Angeles. We'd love to look as close
to the central black hole as possible, so we could
actually figure out how nature is
accelerating these jets and getting them up
to such high speeds. And we'd also like to
know what it is actually that the jets are made of. Because it turns out that's
something that's currently not known. NARRATOR: Until more
is known about blazars, astronomers will keep a
neighborhood watch for them, as well as all the
other dangerous places in our uncontrollable universe. Definitely there are
violent events going on in the universe. Much, much more energy than
we can even imagine on Earth. There are trillions of
suns shining all at once. Those are the kinds of energies
that we're talking about. But in that case, the fact
that we are far away from them helps the survival
of our species. If we were actually traveling
through space, then definitely we will have to be worrying
about these events.
