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foreign
of all the objects in the cosmos planets
Stars galaxies
none are as strange mysterious
or powerful
as black holes
black holes are the most mind-blowing
things in the universe
they could swallow a star completely
intact
powerful jets that just spew matter out
first discovered on paper
on the back of an envelope some
squiggles of the pen the bizarre
solution to a seemingly unsolvable
equation mathematical Enigma Einstein
himself could not accept black holes as
real people didn't even believe for many
years that they existed nature doesn't
work that way
yet slowly as scientists investigate
black holes by
Irving the effect they have on their
surroundings
evidence begins to mount
that is the proof of a black hole
millions of times the mass of the Sun
Cutting Edge discoveries show we did it
black holes are very real I thought it
was crazy I said holy
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but what exactly are they if we could
visit one what might we see with their
immense power do black holes somehow
shape the very structure of the universe
is it possible we might not exist
without them it's
it's quite a journey
black hole apocalypse
right now on Nova
[Music]
there are apocalyptic objects in the
universe engines of Destruction
menacing and mysterious
black holes
scientists who study them find them
astonishing
black holes can sort of blow your mind
I'm amazed that these objects actually
exist
black holes defy our understanding of
nature black holes are the greatest
mystery in the universe
they're completely invisible yet
powerful Beyond imagining
they can tear a star to shreds
black holes actually will eat anything
that comes in their path
really want to avoid them at all cost
s black holes even Slow Time
once thought too strange to be real
black holes shatter are very
understanding of physics
what we're learning they may somehow be
necessary for the universe we know to
exist
they might well be the key players in
the universe
what are these strange powerful objects
outrageous and surprising where are they
and how do they control the universe
the search for black holes is on and it
will be a wild ride across the cosmos to
places where everything you think you
know is challenged where space and time
even reality are Stranger Than Fiction
[Music]
and we're starting that Journey at a
very unlikely place
here at a remote location in Washington
state where for the first time a radical
new experiment has detected black holes
yeah
it originated over 50 years ago when a
few Visionary scientists imagine a
technology that hasn't yet been invented
searching for something no one is
certain can be found the experiment is
daring and risky
failure could mark their lives forever
but they don't fail right here in these
facilities they make a remarkable
discovery
in the early hours of September 14 2015
they record a message
it looks and sounds like this
just a little chirp
but that chirp is epic Monumental the
signal traveled over a billion light
years to reach us
it started far far away
and what it tells us is this
somewhere in the cosmos over a billion
years ago
massive black holes Circle each other in
a fatal encounter
closer and closer they come
swirling faster and faster until finally
they slam together
the black holes create waves that spread
outward
just like vibrations on a drum
a ringing and the fabric of space itself
the Collision creates a massive blast
putting out 50 times as much power as
the entire visible universe
sounds out a wave not of heat or light
or sound but of gravity
this gravity wave is moving its way
through the universe at the speed of
light
the wave Races by stars
supercontinents are forming
microscopic organisms have just appeared
washing over one Galaxy after another
after another
dinosaurs roam the Earth the wave is
still moving it zooms through clouds of
dust and then it nears the Milky Way
galaxy
the ice age is just beginning
we're troglodytes
drawing in caves
the wave reaches nearby Stars
Albert Einstein is in the sixth grade
the wave approaches as close as Alpha
Centauri
at midnight on September 13 2015 it is
as close as Saturn
finally over a billion years after the
black holes Collide the wave reaches us
it strikes a pair of revolutionary new
observatories
sites of the daring experiment
this is ligo the laser interferometer
gravitational wave Observatory
the experiment 50 years in the making
has finally hit the jackpot and opened
an entirely new way of exploring the
universe
for 400 years almost everything we've
observed in space has come to us in some
form of electromagnetic energy
that little chirp is different
what hits the Earth in September 2015 is
a gravitational wave a squeezing and
stretching of the very fabric of space
It produced No Light No telescope could
ever see the Collision
we needed an entirely new kind of
Observatory to detect it
that wave is a new and direct evidence
of one of the strangest mysteries in our
universe black holes
most of us have heard of black holes
they're invisible powerful we're talking
about things that are a billion times
the mass of the sun
physical entity with infinite density
No Beginning No End
they pull things in
and warp light
approach one
and time itself begins to change
gravity is so intense that a moving
clock will tick slower
time will become so slow for you
that you will watch the entire future of
the universe
unfold before your very eyes
fall in
and you'd be squeezed as thin as a
noodle
fabric of space and time like tooth
pick
today we know more about black holes
than ever before
but the more we learn the more
mysterious they become
the most exotic objects in the universe
we don't have the physics to describe
them no matter how well you understand
them they remain unreachable in some
sense
okay
[Music]
so black holes have a pretty Fierce
reputation and if you want a villain for
a sci-fi movie cast a black hole but in
reality what exactly is a black hole and
where do they come from
you might think a black hole is like
this
an object but it's not
it's a hole in the fabric of space
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a place where there is nothing nothing
except gravity gravity at its most
intense and overwhelming
so if black holes are all about gravity
gravity at its most extreme what exactly
is gravity
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we're all familiar with gravity
it's Friday
it rules our lives
even so for a very long time how gravity
actually works was one of the greatest
Mysteries
over 300 years ago Isaac Newton was
fascinated with the behavior of moving
objects
eventually
he figured out his laws of motion they
worked so well we still use them today
but Newton's Laws can only describe
gravity's effects not explain what it is
and here's where Albert Einstein comes
in
Lake Newton he thinks about objects in
motion
and he wonders what gravity actually is
is it a force or could it be something
else
here's what concerns Einstein
take this apple
I can't move it without touching it
but if I drop the Apple
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it moves toward the Earth
but what if I take my hand away and the
floor in the basement and the floor
below that then what happens
the Apple just keeps falling
Einstein realized that gravity had
something to do with falling
now if I throw the Apple
it falls along a curved path
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but imagine I could get the Apple moving
much faster
eventually if I get the Apple moving
really really fast say 17 000 miles an
hour
its curved path matches the curve of the
Earth the apple is in Orbit falling
freely just like the International Space
Station and the astronauts inside it
according to Einstein the apple and the
space station and the astronauts are all
falling freely along a curved path in
space
and what makes that path curved the mass
of the Earth
Einstein came up with a supremely simple
concept and that is that space and time
is Bent by the Earth and by the Sun and
by all the objects in the world so
according to Einstein
mass of every object
causes the space around it to curve
and that was Einstein's conception there
are no forces anymore there's just
objects bending space-time and other
objects
following the straightest line through
it
all objects in motion follow the Curves
in space
so how does the earth move the Apple
without touching it
the Earth curved space and the Apple
Falls freely along those curves
that according to Einstein's general
theory of relativity is gravity curved
space
and that understanding of gravity that
an object causes the space around it to
curve leads directly to black holes
but it's not Albert Einstein who first
makes the connection between gravity and
black holes
it's another scientist
Carl schwartzshield was a German
astronomer head of the Potsdam
observatory in Germany ever since he was
a teenager he had been calculating
complicated features of planetary orbits
Einstein unveils his theory of gravity
in 1915. Carl schwartzshield is in the
German army calculating artillery
trajectories in World War One
and just weeks after Einstein presented
his papers short Shield
then on the Russian front
quickly got a copy and was mapping the
gravitational field around a star
Einstein had gotten at it through a
series of approximations but schwartzel
sitting on the front with bullets and
bombs flying calculated an exact
solution to Einstein's theory and sent
it to Einstein
Einstein was astonished he hadn't even
imagined that you could solve these
equations exactly
but short Shield isn't done
in his solution to Einstein's equations
he discovers something Einstein himself
had not anticipated
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schwartzell said I can calculate this
strange distance from a gravitating
object that represents a kind of a
boundary
schwartzshield mathematically
concentrates a Mass for example a star
into a single point
then he calculates how that mass would
bend space and curve rays of light
passing nearby
as he through his mathematics aimed
particles of light or matter towards
this point
there was this boundary surrounding the
point at which the particles would just
stop
the particles disappeared time stopped
schwartzeld has discovered that a
concentration of mass will warp space to
such an extreme that it creates a region
of no return anything that enters that
region will be trapped unable to escape
even light
it's like those roach motels you can
check in but you can't check out once
you go across that boundary even if you
can sail through there's nothing you can
do to get out there's nothing you can do
to Signal out it becomes this strange
cut off portion of space-time
what Carl schwartzshold has discovered
is that any Mass compressed into a small
enough space creates what we today call
a black hole
Albert Einstein whose own theory of
gravity predicts such a thing cannot
believe it can happen in the real world
Einstein didn't think that nature would
act like this he didn't like this idea
Carl schwartzshield becomes ill and dies
before he has a chance to further
investigate his own Discovery
Twitter in November 9
19 World War One ends the strange
theoretical sphere discovered by Carl
schwartzell seems destined to be
forgotten nothing but a curious
historical footnote
[Applause]
[Music]
and about how fusing Adam's Powers Stars
a process called nuclear fusion
some begin to wonder if something like a
black hole could actually come from a
star
but not just any Star
it would have to be big stars are born
in litters and you get a distribution of
sizes and masses
thousands of little stars and a few big
stars very big stars incredibly massive
stars are in many ways similar to living
creatures
humans they have life cycles
investigating Stars life cycles in the
1930s two Visionaries subramanian
chandrasekar and Robert Oppenheimer this
discover that the most massive stars end
their lives very differently from
smaller ones the life cycle of a star
really depends on its mass
the mass of a star determines what's
going to happen after it finishes
burning its hydrogen fuel
All Stars start out burning hydrogen
the lightest atom using hydrogen atoms
into helium working their way up to
heavier elements
gravity wants to crush the entire mass
of the star but the enormous energy
released by Fusion pushes outward
preventing the star from collapsing
stars are stable because you have an
outward moving pressure due to nuclear
fusion and that's balancing with the
inward force of gravity
smaller stars can't fuse elements
heavier than helium
but in the most massive stars
crushes heavy
all the way up to iron
iron is such a massive element it has so
many protons in it that by the time you
fuse iron you don't get any energy back
out
iron is a dead end for stars fusing
atoms larger than iron doesn't release
enough energy to support the star
and without enough energy from Fusion
keeping the star inflated there's
nothing to fight gravity
and gravity wins
and so the entire star collapses
very rapidly trillions of tons of
material come crashing down hit the
dense core and bounce back out blowing
off the outer layers of the star in a
massive explosion
supernova
The more mass the more gravity
so if the remaining core is massive
enough gravity becomes Unstoppable
known Force to prevent the collapse to
an infinitesimally small Dot
until all its mass is compressed in an
infinitely small point
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a black hole
the theory makes sense but most
physicists remain skeptical about black
holes
Einstein and Eddington all the sort of
you know preeminent astrophysicists in
the 1930s or 1950s did not believe that
they were actually real it remained a
solution a mathematical Enigma for a
very long time so it took a long time
for people to even start looking for
them
it's not until the 1960s that the idea
of a supernova creating a black hole is
taken seriously
Princeton physicist John Wheeler who had
originally been a skeptic begins to use
a name from history for these invisible
objects
black hole
the term black hole actually originates
in India
the black hole was the name of an
Infamous prison in Calcutta
[Music]
still no one has ever detected any sign
of a black hole
then in 1967 graduate student Jocelyn
Bell discovers a strange extremely tiny
dead star that gives off very little
light
a neutron star
cold remains of a stellar collapse the
neutron star gives astronomers more
confidence that black holes much heavier
dead stars might also exist
[Music]
a half century after Carl schwarzshield
mathematically showed that black holes
are theoretically possible
scientists have identified a natural
process that might create them
death of large Stars
so these giant Supernova explosions of
extremely massive stars make black holes
any star that is born with a mask that's
about 10 times the mass of the Sun or
higher
will end in a black hole so our galaxies
replete with little black holes which
are the Stellar corpses of generations
of stars that have come and gone
so what are these invisible Stellar
corpses like
imagine I'm exploring space with some
advanced technology for Interstellar
travel so that we could visit a black
hole maybe one in our own Galactic
neighborhood
[Music]
this particular black hole isn't very
big only about 10 solar masses meaning
10 times the mass of the sun and like
all black holes it has an event horizon
distinct Edge to the darkness that's the
boundary Carl schwartzshield first
discovered where gravity is so strong
that nothing can escape not even light
and that's where we're going
thank you
as we get closer some very strange
things begin to happen
look at the edge of the black hole see
how the image of distant stars is
distorted and smeared into a circle
that's gravitational lensing the black
hole's extreme gravity bends the path of
light passing by so that a single point
of light like a star briefly appears as
a ring around the Event Horizon
I'm now deep in the black holes gravity
well and we're going to start
experiencing the effects the extreme
gravity actually slows down time
relative to the Earth from their point
of view I appear to be slower
but from my point of view time on Earth
is speeding up
now let's say I want to get even Closer
by taking a spacewalk
[Music]
the way the black hole slows down time
is about to get even more pronounced
here I can see the shadow of the Event
Horizon approaching
and my light blinking normally
but watching from the ship
the closer I move toward the black hole
the more slowly I appear to move the
pulses are nearly infinitely spaced
so it looks as though I'm frozen in time
for me everything is completely normal
even when I reach the Event Horizon
if you waited long enough
maybe millions or billions of years the
ship would finally see me disappear
and that's the last you'd see of me
[Music]
what's inside a black hole that's still
a mystery and even if I find out I can
never go back and tell you but I can say
this
black holes may be dark from the outside
but inside they can be bright
I can watch the light from the Galaxy
that's fallen in behind me and that's
the last thing I'll ever see
unfortunately the fun is about to end
now that I've crossed the Event Horizon
I'm falling toward the center where all
of the mass of the black hole is
concentrated
and I'm beginning to get stretched
as I fall in the gravitational pull at
my feet is stronger than at my head and
my body is starting to get pulled apart
I'll be stretched as long and thin as a
noodle spaghettified and ultimately I'll
end up completely disintegrating into my
fundamental particles which are then
crushed to an infinitely small point
Singularity where everything we
understand about space and time breaks
down
or maybe the black hole less than 40
miles across on the outside
is as big as a Universe on the inside
and as I pass through my particles will
join the primordial soup of a new
beginning
so that's what theory tells us we might
experience if we could travel to a black
hole
[Music]
but how can we know for sure
how do you investigate something you
can't even see
there are ways to investigate if
something is happening somewhere even if
I can't see that thing directly take
Yankee Stadium
what's happening inside there is there a
game going on I can't see the field I
can't see any players or baseballs or
bats but I can definitely tell if
there's activity around the park
it's pretty clear something is going on
[Music]
I can learn just by observing The
Happening happenings around the stadium
and these do look a lot like Baseball
fans
[Music]
[Applause]
and that's the way we investigate black
holes by observing the effect they have
on their surroundings
but what sort of effects
how might a black hole reveal itself
starting just before World War II two
Monumental discoveries are about to
radically change astronomy
in 1931 Bell Labs engineer Carl jansky
picks up mysterious radio waves
emanating from deep space
then the sky gets even stranger
when scientists melt Geiger counters
uncaptured German rockets and discover
the cosmos is also full of x-rays
these discoveries give astronomers
important new tools that will
revolutionize the hunt for black holes
and dramatically expand our vision
what our eyes can perceive is a very
narrow part of the electromagnetic
spectrum
if the electromagnetic spectrum were
laid out along the Brooklyn Bridge the
portion we can see with our eyes would
be just a few feet wide
electromagnetic radiation includes waves
of many different frequencies
radio waves microwaves infrared and
ultraviolet light X-rays and gamma rays
radio and x-ray astronomy open up the
sky revealing dim or even invisible
objects blasting out powerful energy no
one knew was there
they began to realize that this very
Placid thing that we see out there all
this very quiet thing that looks like
nothing is happening and the only thing
that's moving is the planets found out
that there was Madness going out there
was chaos out there
x-rays come from the high energy end of
the spectrum
what is creating all this energy
this much is certain whatever the source
it is invisible to ordinary telescopes
and it is hot
x-rays come from things which are at
temperatures of millions of degrees even
tens of Millions
one of the first of these x-ray sources
to catch the attention of astronomers is
named cygnus X1
sickness it was in the constellation
cygnus X it was an x-ray Source One it
was the first one you found
in 1970 Paul murden is a young English
astronomer trying to secure his next job
I was a research fellow I was coming to
the end of my three-year contract and I
thought what can I contribute to finding
out what these things are
Merlin Works in a 15th century Castle
surrounded by telescopes
a Royal Observatory
using the largest telescope in England
he begins searching the area of the
constellation cygnus
swan
he decides to hunt for pairs of stars
pairs of stars are called binaries they
may sound exotic but they're not at all
uncommon
many of the Stars we see perhaps half
are actually binaries pairs of orbiting
Stars locked together by gravity
murdered wonders is it possible there
are binaries where only one of the stars
is visible
I thought that maybe there was a kind of
a star system in which there was a star
a northern one ordinary star that made
light and then there was another star
nearby that made x-rays
The Telltale sign of a binary is that
the stars are moving around each other
so murden begins searching for a visible
star that shows signs of motion
sometimes it's coming towards you
sometimes it's coming away sometimes
it's coming towards you sometimes coming
away
when the star is moving toward us it
appears more blue
wavelength of its light gets shorter
moving away it appears more red as the
wavelength of its light gets longer
this is known as Doppler shift
[Music]
after looking for color changes in
hundreds of stars in the area of cygnus
murdon spots a possible suspect a
visible star whose light is Shifting as
though moving around
it very clearly was a binary star a
double star
the star was moving around and around
with a period going around once every
5.6 days
but whatever it's
good there was no Trace in the spectrum
of the second star
there was one start there that wasn't
the second star there
Merton has a binary pair in which only
one star is visible
the second object emits x-rays has
enough mass and gravity to dramatically
move a star but gives off no light
could it be the corpse of a star massive
enough to become a black hole
The crucial issue in deciding whether
cygnus X1 was a black hole was to
measure the mass of the X-ray emitting
object
it would have to be very massive at
least three times the mass of our sun if
not it's probably just a neutron star
collapse star that's dense but not heavy
enough to be a black hole
so The Observers needed to come up with
a conclusion that the dark object the
X-ray animating object in cygnus X1 was
heavier
hopefully substantially heavier than
three solar masses
from his observations Merton is able to
make an estimate of the mass of the
invisible partner
and the answer came out to be
six times the mass of the Sun
so there was a story then that cygnus X1
was a black hole and the key to the
argument was that the mass of the star
you couldn't see
was more than three solar masses
where I'd finished writing it all out I
sat back and thought
it's a black hole
[Music]
this would be the first actual detection
of a black hole
it's a huge claim and Merton will have
to convince Skeptics starting with his
boss
on the Royal
Sir Richard Wooley he didn't really go
for black holes
it's all fanciful a lot of people in
California were talking about this
there are a lot of funny people in
California you know a lot of hippie type
people
people like
theorist Kip Thorne
so I was nervous about I was nervous
about the scale of the um of the
discovery and actually so were other
people all around me
I was working with a fellow scientist
Louise Webster
and we were modest about the claim that
we were making because we knew
what people would think of it
and if you look at the paper we
published it just mentions the word
black hole once right at the end
we think this might be a black hole
the Palmer and Louise Webster paper
appears in September 1971. other
astronomers agree it could be a black
hole
but no one knows for sure
three years later Kip Thorne and the
noted British physicist Stephen Hawking
make a now famous wager about cygnus X1
we made a bet as to whether cygnus X1
really was a black hole or not
the bet is partly ingest both men hope
it is a black hole
but Hawking not wanting to jinx it vents
against his own wishes
[Music]
and I claim it is a black hole and
so we signed that bet in December 1974
and gradually the case that it really
was a black hole became stronger and
stronger and stronger so in June of 1990
Stephen broke into my office and he
thumb printed off on this bed Conceited
the bet in my absence I came back from
Russia and discovered that he had
conceded
Now by 1990 the evidence of cygnus x1's
mass may be strong enough to settle a
bet between two friends
but the original estimate wasn't precise
enough to be definitive
in order to calculate mass Paul Merton
had to rely on rough estimates of the
distance to sigus X1 which varied by a
factor of 10.
and the question wouldn't be answered
for another 20 years until astronomer
Mark Reed became intrigued by the puzzle
[Music]
an astronomer at the Harvard Smithsonian
Center for astrophysics when he sets out
to conclusively prove that cygnus X1 is
a black hole by measuring its precise
Mass
thank you
but how can you measure the mass of an
invisible object using laws developed by
German astronomer Johannes Kepler in the
1600s it's possible to calculate the
mass of a celestial object but only if
you know its distance
in astronomy is absolutely fundamental
if you don't know distance you don't
know what the object is
could be a very nearby Firefly like
thing it could be a very distant huge
star much much bigger than the Sun
so to get the true precise Mass
this XY and confirm that it is a black
hole Reed needs to know how far away it
is
but how can he measure the distance to a
star
the secret lies in a familiar phenomenon
parallax
it's what our eyes and brains use to see
in three dimensions
you can put your finger up at arm's
length
look at it and close one eye I'm closing
my left eye and I'm looking at my finger
relative to the wall in the background
there
and now if I open my eye close my right
eye
I see my finger has appeared to move
with respect to the original position
and that's because our eyes are
separated and we view from different
Vantage points
to use parallax to measure distance to
an object in the sky astronomers let the
motion of the earth provide the two
different Vantage points
imagine cygnus X1 is right here and the
Earth and the Sun are over there now the
earth goes around the Sun once a year
and in the springtime the Earth ends up
on one side of the Sun and we observe
cygnus X1 along a ray path like this
and six months later
the earth goes around the Sun
to the other side we get a different
vantage point from cygnus X1
now he has a triangle that goes between
the Earth at its two positions
and cygnus X1
we know the base of the triangle the
diameter of Earth's orbit
and the principles of geometry tell us
that all we need to calculate the
distance is the size of the angle at the
top
and we measure this very small angle
here at the point at cygnus X1 and then
from direct geometry we can calculate
the distance to cygnus X1 and from that
and for a very accurate Mass the concept
is simple but cygnus X1 is so far away
that the angle to be measured is
minuscule a tiny fraction of one degree
it's smaller than the angle span by
Abraham Lincoln's nose on a penny in San
Francisco
viewed from New York
because the angle is so very tiny it
can't be measured by any one telescope
[Music]
but Reed's team has a solution
we take 10 radio telescopes that are
spread across the continental U.S and to
Hawaii and to Saint Croix in the Virgin
Islands we use these telescopes
simultaneously and we synthesize in a
computer
telescope that has the diameter of the
size of the Earth that gives you
incredible angular resolution
using this technique Reed's team
determines that cygnus X1 is 6 thousand
light years away
with the new distance we got the 6 000
light year distance we were able to
determine that the mass is about 15
solar masses easily a black hole
40 years after it was identified as a
possibility cygnus X1 is now widely
accepted as the first confirmed black
hole it's an understated paper and the
fact that my name was on it and Louise
Webster's was on it did us a lot of good
in our careers
I think as a result of this discovery I
got offered a permanent job and it was a
great celebration for the family
so it worked out very well for me as
well as getting the intellectual
satisfaction of
solving a problem
[Applause]
so finally after years of speculation we
have a real black hole
not only that but a black hole that's
blasting out X-rays and has a companion
star
if we could visit in my imaginary
spaceship what would we see
[Music]
since to cygnus X1 has been established
at 6 000 light years from earth and its
mass is 15 solar masses or 15 times the
mass of the sun
and cygnus X1 is surrounded by an
accretion disk a disc shaped cloud of
gas and dust outside its Event Horizon
the point of no return as gravity pulls
matter toward the black hole the cloud
starts rotating just like water being
pulled down a drain
within that accretion disk particles
closest to the black hole whip around at
half the speed of light it's like a
giant particle accelerator in space
but why does it emit x-rays
as those particles race around they
Collide which Heats them up to millions
of degrees
when they get that hot particles blast
out X-rays and it's those x-rays that
first let astronomer Paul Merton to
investigate this black hole nearly five
decades ago
and there's something else about cygnus
that's different
it has a companion star
this blue supergiant star orbits the
black hole once every 5.6 days
it orbits so close to cygnus X1 that the
black hole strips material off the star
and pulls it into the accretion disk
some of that material will cross the
Event Horizon and get swallowed up
but not all of it
some of the stuff actually comes back
out before ever entering the black hole
kind of like a toddler eating half the
pasta ends up on the floor half of it
maybe on the ceiling and some of it in
the mouth
one of the most striking and enigmatic
features of cygnus X1 is its enormous
jets these beams of particles and
radiation stream outward from cygnus's
North and South Poles perpendicular to
the accretion disk
still a lot we don't know about these
Jets but they are tightly focused and
extremely powerful blasting out at
nearly the speed of light and extending
well beyond cygnus
when gas gets to these high temperatures
and produces the light
there's also a little bit of a magnetic
field that forms around them and we
don't understand exactly how but these
magnetic fields help collimate these
massive outflows from black holes
powerful hoses if you will that just
spill matter out
so that's cygnus X1 if we could see it
up close
a growing feeding black hole with huge
Jets blasting particles way out into the
universe
they're almost these breathing fire
eating demons if
flicker they have bursts it's a very
violent Fireball very active
what was once a bizarre mathematical
Curiosity has now become quite real
after Decades of skepticism scientists
now accept that burned out corpses of
large Stars can trap light inside them
warp space and time around them attract
matter and accelerate it to
mind-boggling speeds
black holes seemed like such a radical
idea that we shouldn't accept it but bit
by bit the evidence for black holes has
gotten stronger and stronger and we've
seen these amazing things
at least 20 black holes have been found
in our galaxy
x-ray binaries like cygnus X1
and there are probably Millions more of
these massive Stellar corpses in our
galaxy alone
still a stunning surprise awaits
everything astronomers think they know
about black holes and much of what they
believe about the universe itself will
be upended by a shocking discovery
the revelations begin when radio
telescope surveys of the sky detect
mysterious hot spots emitting radio
energy
they were coming from what looked like
stars
because these objects resemble stars but
were discovered through radio signals
astronomers name them quasi-stellar
radio sources quasars
but are they stars or not the first step
in investigating them is to figure out
what they're made of
[Music]
astronomers analyze the electromagnetic
energy they emit
every element has a unique spectral
fingerprint for example carbon
[Music]
helium
hydrogen
these lines reveal the chemical makeup
of a star
but the spectrum of a quasar turns out
to be incomprehensible
they looked at it and it was gibberish
it didn't look like there were any
emissions from elements that they knew
what are they missing
there has to be a clue somewhere
finally in 1963 Caltech astronomer
Martin Schmidt finds it hiding in plain
sight buried in the Quasar spectrum is
the fingerprint of hydrogen
he noticed something familiar but it was
in the wrong place
Prince of hydrogen had been shifted way
off to the red
it was hard to spot because the spectral
lines of hydrogen
were radically shifted toward the lower
frequency end of the spectrum and that
could only mean one thing
Quasar is moving away from us at
Fantastic speed
but astronomers have almost never before
seen light shifted to such an extreme
[Music]
like a familiar sound shifting too low
to understand and
the light from quasars has shifted to
such a degree
that hydrogen is unrecognizable
this extreme amount of shift means
quasars are racing away from us at
blinding speeds the reason it's the
legacy of an event that occurred almost
14 billion years ago the Big Bang
beginning of our universe
and ever since the universe has been
expanding caring with it all the objects
it contains including quasars almost no
one had ever seen anything moving away
at that high speed this made this object
almost the furthest away thing that had
ever been seen which meant the thing
itself had to be so luminous and you had
to account for that
2 billion light years away putting out
the energy of a trillion Suns each
second
what could possibly create that
no one had any idea what could be
powering these things where could all of
this energy come from if you work out
through calculations it can't be
chemical energy
they knew it couldn't be nuclear energy
there's no way a quasar could be a star
no amount of nuclear fusion could
produce that much star power the only
engine
possibly put out that much energy is
gravity
[Music]
gravity
in everyday life we can overcome gravity
easily
but when concentrated to an extreme buy
a black hole gravity is overwhelmingly
powerful
a handful of scientists start wondering
could quasars perhaps be powered by
gravity engines what if the energy
blasting out from quasars is coming from
Bright accretion disks around black
holes
[Music]
produce that kind of energy that kind of
brightness it has to involve a black
hole
but not just any black hole
whatever was the source of the emission
from a quasar had to be massive
how massive well millions or billions of
times heavier than the Sun
millions or billions of times heavier
than the Sun
cygnus X1 is only 15 times the mass of
the sun
the black holes powering quasars are an
entirely different category of black
hole
super massives
and they seem to be located in the
centers of galaxies
but what about our own Galaxy
could there be any supermassive black
holes closer to home
Center where any supermassive would be
found lies in the direction of the
constellation Sagittarius
the Archer
now Sagittarius isn't just any
constellation it's in the direction of
the center of our own Milky Way galaxy
we live inside the Milky Way we can't
see the Galaxy the way a space traveler
would
[Music]
but I can use my trusted imaginary Star
machine to show us the Galaxy from the
outside
our home is a spiral galaxy hundreds of
billions of stars drawn together into a
gigantic disc
it's wide about a hundred thousand light
years across but it's relatively thin
only about a thousand light years thick
and the whole spiral slowly rotates
our solar system is here
and here 26 000 light years from the
Earth is the center which we see in the
direction of Sagittarius
in this Dent Center there are millions
of stars and lots and lots of dust and
gas
so that's the view of our galaxy from
the outside thanks to my imaginary
technology but since we live inside the
Milky Way when we look towards the
center we're looking through much of our
own Galaxy which means it appears to us
as a band of stars and dust across the
sky a Milky Way
[Music]
deep inside this band of stars and dust
could a supermassive black hole be
lurking
in the 1990s astronomers grow determined
to solve the mystery to hear through the
murky Milky Way and learn what if
anything is at its Center
one of them is Andrea guests
guest takes on a daunting challenge
she will try to track individual Stars
orbiting the center of the Galaxy
the essence of this experiment comes
from watching stars orbit the center of
the Galaxy
so you want to find the stars that are
as close to the center of the Galaxy as
possible
which means that I want to get access to
the largest telescope I can possibly get
my hands on
and that means coming here
[Music]
the summit of Mauna Kea a dormant
volcano almost 14 000 feet above the
beaches of Hawaii
high altitude and low humidity make this
the ideal place for astronomy
[Music]
Keck Observatory one of the largest in
the world
but despite its size Keck has the same
problem as all telescopes on Earth
[Music]
atmospheric distortion
think about looking at a pebble at the
bottom of a river
the river is moving very quickly and
your view of that pebble is distorted
like a river the Earth's atmosphere is
constantly changing bending light like a
fun house mirror
to compensate for this Keck Pioneers the
scientific use of a Declassified
military technology called Adaptive
Optics
first they shine a laser into the sky
creating an artificial guide star
the turbulent atmosphere distorts the
guide star
pewter knows what it should look like
and adjusts the telescope mirror
accordingly
you look at yourself in a circus of
funhouse mirror you look completely
distorted and the goal of the Adaptive
optic system is to introduce a second
mirror that's the exact opposite shape
and make you look flat again
[Music]
very deep inside the telescope the
deformable mirror changes shape up to 2
000 times a second to reverse the
atmosphere's distortion
and it has allowed us to take the
sharpest images ever obtained of the
center of the Galaxy
the sharpness of those images allows Gaz
to make out individual Stars near the
center a huge advance in astronomy she
begins recording their positions in
1995. and every year since then we've
taken an image just take a picture
putting those annual snapshots together
creates a time-lapse movie of Stellar
orbits
and what those movies reveal is
astounding
the stars are whipping around the center
of the Milky Way at phenomenal speeds
are moving at several thousand up to ten
thousand kilometers per second or 10
million miles per hour they're they're
really hauling to go that fast the stars
must be orbiting something extremely
massive
the mass that we infer is 4 million
times the mass of the Sun what could be
four million times the mass of the Sun
yet be completely invisible that is the
proof of a black hole
and not just any black hole a
supermassive silent and sleeping right
in the center of our own Galaxy
in fact this is the best evidence to
date that we have for the existence of
supermassive black holes not only in the
center of our own Galaxy but anywhere in
the universe
[Music]
supermassive black hole four million
times the mass of the Sun and the very
center of our own Milky Way galaxy
from a cosmic perspective it's right
next door
and it raises a profound question there
are billions of galaxies out there if
ours has a supermassive black hole at
its Center and if Cuisines are found at
the centers of their galaxies what about
the others
are there black holes at the centers of
galaxies if they are how common are they
we simply didn't know
could astronomers ever hope to find what
lurks at the centers of other galaxies
millions of light years away as guests
did in our Milky Way
it would take another innovation in
astronomy to make that possible
discovery
when the Hubble Space Telescope starts
delivering clear images of distant
galaxies a team of astronomers gets to
work
they become known as the nukers because
their focus is galactic nuclei the
centers of galaxies
one of them is Todd Lauer
step one we take a picture of the Galaxy
with the Hubble Space Telescope
it shows us where the stars in the
galaxy are tells us its structure and
exquisite resolution
key to finding supermassive black holes
is to learn how fast the stars in the
galaxy are moving
galaxies outside our own are much too
far away to measure the speed of
individual stars but by analyzing the
way light is shifted from Blue to Red at
different points in the Galaxy
astronomers can put together an average
speed of stars orbiting the center
accurate enough to create a replica in a
computer
Second Step where
is to try to model the observations and
we actually do that by building models
of galaxies in the computer
it's known as short Shield's method
developed by Princeton astronomer Martin
schwartzshield son of Carl schwartzell
his mathematics first described the
possibility of black holes
Martin schwartzfield's trick was he
would actually build up
a model of the Galaxy that not only had
where the mass was but it also had how
the stars were moving
for each Galaxy they investigate the
nuker's painstakingly build a computer
model and then using trial and error
adjust the parameters of mass and
velocity
trying to make the model match the
original observations they got from the
Hubble
okay let's try a star here let's try one
over here let's have it go around this
way let's have this one go around that
way and we do this thousands and
thousands of times until we build up a
library of how stars in orbit in this
galaxy
is when observations of the model
match the observations taken with the
Hubble Space Telescope
that doesn't happen
the models are missing something
we try it again and again and again all
with no black hole yet and see gee we
really can't get the observations
explained by the model
only when they add an enormous invisible
mass at the Galaxy Center does the model
match the Hubble observations
almost always we have to put in a black
hole at the center
we can't match the observations without
a black hole in the model
of roughly three dozen galaxies that the
nukers investigate virtually all of them
require a supermassive black hole
that other observations have made us
even more certain that supermassives and
galaxies go together
every Galaxy we've looked for one we
have found a supermassive black hole in
its Center
it's a stunning revelation
supermassives once an entirely
unexpected category of black holes may
be common
not only the center of our galaxy but of
all galaxies
take Galaxy M31 also known as the great
Andromeda Galaxy
two and a half million light years away
on a clear night you can see it from
Earth
but even with the Hubble Space Telescope
we can't make out precise details of its
Center still we're pretty sure there's
something extremely massive hiding there
what if we could take a closer look what
if we could visit a galaxy far far away
[Music]
thank you
as we enter the outer part of Andromeda
we're still too far away to see what's
lurking at the center but we can make
out a dense cluster of stars in the core
and that could be a sign that there's a
giant black hole nearby
billions of years ago it would have been
surrounded by gas and stars and other
small black holes
the black hole may have powered a quasar
mad be blasting out blinding radiation
over hundreds of millions of years it
would have consumed all the available
gas and the closest Stars
[Applause]
foreign
but it has some distinctive features
we've never seen before
first it's colossal
if it were dropped in our solar system
Mercury Venus Earth and Mars would all
be trapped inside the Event Horizon
that's big but it's nothing compared to
the sheer Mass a hundred million times
the mass of the sun
and the destruction won't end there
Jupiter won't last long the
gravitational field of the supermassive
will grab hold and swallow it whole
eventually Saturn will suffer the same
fate
the outer planets might survive but in
cold and dark orbits
this black hole rotates rapidly
distorting and dragging the fabric of
space-time
like all black holes The Event Horizon
is completely featureless
remember there's nothing there it's just
a boundary that conceals the interior
but the accretion disc can tell us a lot
about what's going on
that's the fiery ring of gas and dust
around the black hole
to explore the accretion disk
the disc is spinning at an incredible
speed as much as half the speed of light
if Jupiter moved that fast it would
complete its entire orbit in a few hours
the region around the black hole is a
cosmic tornado
this warm is caught in the Whirlwind too
they're like tracer
Tracer storm to map movement
the middle robot can send us images it's
Following the Leader like a race car
speeding around the track
from here the extreme warping of
space-time around the black hole plays
crazy tricks on our eyes
it looks like there's one accretion disc
whipping around the equator and another
arcing over and under the poles
but that's an illusion
the black hole's extreme gravity bends
the path of light emitted behind the
black hole and makes it look like the
accretion disk is both above and below
there's actually nothing around the
poles it's just the passing light rays
that's gravitational lensing again
drawing much closer to the event horizon
the gravitational lensing would become
so extreme that one of my robots could
look straight ahead and eventually see
its own back the light forever trapped
in an eternal Circle
so that's our tour of the supermassive
black hole at the center of the
Andromeda Galaxy
pretty amazing
also amazing nothing in the mathematics
LED scientists to imagine that black
holes could get that big
as strange as they are ordinary Stellar
Mass black holes were at least predicted
by Theory
supermassives are a complete surprise
for the Stellar Mass black holes people
thought about them from a theoretical
perspective
and then we found them observationally
this supermassive black holes this story
has been inverted we've actually found
evidence of them observationally first
and now we're working on the theory of
how did these things come into being
we already know that stars can collapse
to create ordinary black holes
supermassives are bigger by many orders
of magnitude
cygnus X1 is 15 times as big as our sun
supermassive at the center of our Milky
Way is 4 million times as big as our sun
the one in the Andromeda galaxy is a
hundred million times as big as our sun
and it's not the biggest not even close
there are super massive 10 even 20
billion times the mass of our sun
thank you
how is it possible to make such gigantic
black holes
could supermassives have come from
collapsed Stars
that seems very unlikely we don't know
any stars billions of times bigger than
the Sun
we know about black holes you might get
from a dying star they have several
times the mass of the Sun contained
within them but millions of times the
mass of the sun
if that's the case a dying star cannot
have possibly made it
so do these super masses
millions or even billions of times
heavier than the sun somehow just grow
packing it on like voracious Giants
the wild thing about black holes is that
they feed
they're constantly devouring anything
that comes within their sphere of
influence so they grow
but how exactly do they grow
what do they eat and where do they find
it
we believe that black holes grow by
accretion of gas and the way this works
is that you have a lot of gas around in
the center of a galaxy and this gas
would then assemble and form an
accretion disc
the accretion disc is made up of
hydrogen helium and other elements in a
gaseous form the immense gravity of the
black hole pulls the gas in toward it
as it swirls around it orbits closer and
closer to the black hole and the feeding
begins
stuff in the inner regions would get
slowly pulled in sped up will reach the
Event Horizon and then that's it
[Applause]
whatever gas crosses the Event Horizon
disappears forever
the black hole has absorbed that
material
so it actually adds to the mass of the
black hole
this is one way a black hole can grow
gradually nibbling gasp and dust
but it's not the only way
cygnus X1 has been slowly stripping
Material off a nearby star
process that will likely go on for
thousands or millions of years
but what if a black hole could rip an
entire star apart in just a matter of
years or even weeks
that would be a very violent event and a
team of Space Explorers is on the
lookout
operations control center for a Space
Telescope I'd be five by five how many
we show beginning of track at zero three
Thirty the Chandra x-ray Observatory
16 minutes one six
orbiting up to 86 000 miles above the
Earth Chandra takes high resolution
images of objects that emit x-rays
this is one
a short-lived extremely violent event
called a transient
fascinates James gioshon
supernova
destruction of planets by their host
Stars I'm just fascinated with
destroying things for science
is investigating a mystery discovered by
a colleague Lin this blur on James's
screen is actually a massive sudden
burst of X-ray energy caught by accident
this little smudge popped up in the
background of this image and given its
great distance it's actually
tremendously bright
could it be