Hey, Vsauce. Michael here.
This symbol, commonly called a Yin Yang
symbol, is a taijitu meaning diagram
of the supreme ultimate. The principal
of Yin and yang, opposites existing in harmony,
is associated with ancient Chinese philosophy.
But the very first use of the iconography, the classic symbol,
actually comes from a shield pattern used by the ancient
Romans seven hundred years before its first
known use in China. A connection between the two
has yet to be found. Regardless of who came up with it first,
the symbol was a bright idea. But what's the brightest object in the entire universe?
Well, apparent magnitude.
Commonly used when stargazing refers to how bright an object
appears to us, say, when looking up from Earth.
It depends on Earth-centric factors, like how close the object is
to our planet. Magnitudes are logarithmic
and arranged like golf, where a smaller number
means a greater brightness. But today
I'm looking for absolute magnitude,
a measure of how bright things all over the universe near
and far would be if we looked at them from the same distance.
Absolute magnitude will guide us to the most blinding
light in the universe, irrespective of it looking faint
to us here on Earth, just because it's far away.
The difference is significant. A 100-watt light bulb
placed closer than 8 centimetres - about 3 inches - from your eye
will appear brighter than the Sun in the sky.
But that's not fair. If you could see the Sun and the bulb
from the same distance, the Sun would be a septillion times brighter.
That's bright. But the Sun
shines punily compared to the rest of the cosmos.
If you could line the Sun up with everything else out there,
giving every star and cosmological phenomenon
a fair chance, the Sun's absolute magnitude
would be 4.8. Not bad. But check out
R136a1. This nuclear fuelled beast isn't
the biggest star in terms of volume but it's 256
times more massive than our Sun. It's the most massive star
ever found and it's also the brightest.
Remember that lower absolute magnitudes are brighter.
R136a1 isn't 4.8,
like our Sun, it is -12.6,
which means it is 8.7 million times brighter
than our own Sun. But R136a1
isn't the brightest thing out there. When a giant star dies, it explodes violently
in what is known as a supernova
or hypernova. As I mentioned in my video
'How Hot Can It Get?', supernovas can eject terrifying flashes of
radiation known as gamma ray bursts. Arguably,
the brightest electromagnetic events in the universe.
A typical gamma-ray burst releases as much
energy in a few seconds as our Sun
will release altogether in its entire
10 billion year lifetime. If WR104,
a gamma-ray burst future candidate, directly struck
Earth with such a beam for only 10 seconds
astronomers predict it could deplete 25% of our
ozone layer and lead to mass extinction and starvation.
The largest thermonuclear bomb ever detonated
didn't do anything close to that and it was exploded right
here, in our atmosphere. Whereas WR104
is eight thousand light years away. You can't even see it with your naked eye
or a pair of binoculars. But gamma ray bursts are merely brief
events lasting only a few minutes at most, sometimes
just a matter of milliseconds. If you want the brightest
sustained thing, you'll paradoxically have to look
at the darkest thing. Black holes.
To be fair, dark matter is ostensibly
darker. But because dark matter has been hypothesized
to not even interact with light, with electromagnetism
at all, calling dark matter "not bright"
is kind of like calling your peanut butter sandwich
"a not fast airplane". It's not really even in the same category.
Black holes, however, do interact with light;
reflecting so little, well, they don't let any
escape, at least not in a form resembling the way
it came in. That's dark.
But the intense energies created by black holes in the process of eating
things like stars
is anything but dark. Gas and debris from the stars they eat swirl into
arcipluvian cosmic gallows known as accretion discs
before making their final death plunge into the black hole.
In the disc, debris spins at unfathomable speeds, pulled around by a black hole
billions of times more massive
than our Sun. Friction in the accretion disk generates heat
on a level difficult to fully appreciate.
Just as hot things glow, the disk does too.
So brightly it has its own name.
A quasar. Quasars shine thousands of times more brightly
than even the brightest stars.
I'm kidding, it's scarier
than that. Quasars shine thousands of times more brightly
than galaxies containing billions of stars.
The first identified quasar, 3C 273, has an absolute magnitude
of -26.7, making it
four trillion times brighter than our Sun,
about 100 times more luminous than the total amount of light produced by the
entire Milky Way. If you put 3C 273
33 light years away from us it would shine as brightly as our Sun -
a mere 8 light minutes away. Blocking the brightness of a quasar with the corona
graph reveals that quasars exist in the centers of galaxies
that are larger than them in area, but are, nonetheless,
drowned out by their light.
Such galactic centres are called active galactic nuclei.
The bulk of their energy spewing forth in the form of a powerful radiation jet,
the length of which puts even
our solar system to shame. The visible part of the jet
in this photograph, for instance, is so long it could stretch from the Sun
to Pluto and back, one-and-a-half million times.
Now, specifically, if a large portion of this ajected energy heads toward Earth,
it's responsible for what we call a quasar.
But if Earth is right and the active galactic nucleus' sights,
it's got a scarier name: a blazar.
And it's blazar 3C 454.3 that clocked in the greatest brightness
ever observed. At historically high levels of activity it registered in
absolute magnitude of -31.4.
To put the brightness of quasars
in yet another perspective, take a look at the one hundred thousandth
picture snapped by the Hubble telescope.
This is a star a few hundred light years away.
And this thing looks just about as bright,
but it is a quasar.
9 billion light years away.
Why are quasars so far away?
Well, a quasar is not forever.
They are billions of light years away,
which means the light we receive from them, the pictures we take of them,
are pictures of things happening billions of years ago.
They represent a phenomenon more common
early in the universe's history, when monster black holes hadn't eaten
all the stars around them to fuel their accretion discs and
before those holes became too fat to be active.
Neil deGrasse Tyson points out that in order to remain
a quasar producer, a black hole must consume
about 10 stars a year. Many
consume more than a thousand stars a year, 600
Earths worth of matter every single minute. The more
stars a black hole consumes, the larger its event horizon becomes
until, eventually, it no longer shreds stars apart
to fuel an accretion disc. Instead, it just swallows them whole
in one dimmer, but still terrifying, gulp.
Quasars are some of the most ancient things in our universe.
If you could teleport instantaneously to one right now
faster than light, it would most likely no longer be burning. What we see
are just their ghosts. Light that left when they were
active that traveled longer than they could live.
But quasars can still be born. They can even be born
right here, in fact. In my video
'What Will We Miss?' I pointed out that the Andromeda Galaxy
is headed our way.
In 3 to 5 billion years it will collide
with our own galaxy, the Milky Way. And the collision
could rearrange stars near the galaxy's central black holes to be consumed,
reigniting a quasar right here, in our galactic backyard.
Funny enough, right now very few of us even see
Andromeda, even though all you need is your unaided eye.
Light from our cities drowns out the night sky like a
quasar drowns out its host galaxy. Artist Thierry Cohen mocked up what big cities
would look like if all their lights were
off and the sky above them could be seen
fully. New York, Hong Kong, Shanghai,
Tokyo, Los Angeles. It's beautiful
and rare. In the 1990s,
during a blackout in the city of Los Angeles, a number of residence
actually called the police they were afraid of mysterious glowing clouds
hovering above the city. They were seeing
our galaxy for the first time in their lives.
At night, artificial lights allow us to see
what's around us but we lose
what's above us. The brightest places
have the darkest, emptiest skies.
There's Yin and Yang again. A taijitu has actually been lurking in this video
the entire time.
The brightest things in the universe, quasars,
are caused by the darkest things in the universe -
black holes. The process that unshackles the most light
is caused by the thing that best imprisons it.
And as always,
thanks for watching.