From Earth, the night sky appears
ethereal, peaceful. It's so far removed
from human civilization. You'd be
forgiven for thinking we're immune to
anything going on up there. But that
couldn't be further from the truth. We
are under attack. Cosmic rays are
bombarding us from every direction. tiny
particles that collide with our planet's
atmosphere, setting off a chain reaction
of ionization that can render our
satellites and other electronic
machinery useless. But where do they
come from? For hundreds of years,
astrophysicists have searched in vain to
find the origin of these elusive
attackers with little success. Even the
type of source has evaded their
searches. But now, thanks to a whole new
field of research, we're starting to
find answers. Not only do we now know
what to look for, but they are proving
more powerful than we ever imagined.
What in the cosmos is possibly capable
of producing a quadrillion electron
[music] volts of energy? I'm Alex Mccoan
and you're watching Astramm. Join me as
we follow the trail of cosmic rays,
leading us right to the limits of
physics as we know it. We'll see how
scientists detect the highest energy
particles in the universe and meet a new
class of astronomical objects whose
extreme behavior until recently seemed
like the stuff of science fiction.
The Milky Way is full of energy, but our
eyes can only detect a tiny fraction of
it. Beyond the spectrum of visible
light, charged particles can give off
higher energy radiation in the form of
X-rays and gamma rays, creating a mess
of energetic fingerprints [music]
throughout space.
Astronomers can forensically decode
these cosmic clues to understand the
flow of energy through our galaxy. But
among these charged particles, there is
one group in particular that remains
clouded in mystery.
Back in 1912, the Austrian physicist
Victor Hess made a historic air balloon
ascent up to 5,300 m where he could
measure the rate of ionization in the
upper atmosphere, or how quickly atoms
and molecules are becoming charged. He
expected to find that it decreased at
higher altitudes, confirming the
prevailing theories at the time.
However, this was not to be.
Unexpectedly, Hess recorded a rate of
ionization that reached three times
higher than at sea level. This led to
the realization that the ionizing
radiation he had dedicated his career to
studying came not from Earth, but from
space. He had discovered cosmic rays and
they did not come in peace. Earth is
under constant barrage from them. These
high energy particles, mostly protons,
travel at nearly the speed of light and
collide with our planet's atmosphere,
sending a shower of secondary particles
down onto its surface. These attacks can
do some serious damage. The secondary
particles produced in cosmic ray showers
the likes of muons, neutrons, electrons,
posetrons and gamma rays can interact
with living organisms contributing to
genetic mutations and radiation damage.
And when cosmic rays interact with
satellites or other orbiting
electronics, they can trigger a bout of
ionization that can cause the circuits
to degrade or even fail
catastrophically.
And they are not only a nuisance to our
best space equipment. Cosmic rays have
meddled with our best scientists, too.
For more than 100 years, the question of
where cosmic rays come from has been one
of the major unsolved mysteries in high
energy astrophysics. Their physical
properties make them almost impossible
to track. Magnetic fields bend their
path before we can locate their origin,
and they break down into a shower of
particles before we can learn their
identity.
These challenges are laid bare when
scientists try to measure the cosmic ray
spectrum. If you plot the number of
incoming high energy particles as a
function of their energy, you notice a
distinct steepening point known as the
knee beyond which the really high energy
cosmic rays above four pa electron volts
are much less common. At first, some
scientists assumed that this knee must
mark the boundary between cosmic rays
coming from inside our Milky Way and
those coming from beyond. Others simply
didn't know. But just as scientists were
about to accept defeat, one observatory
stepped in to revolutionize the search
for these sneaky interlopers.
The large high alitude air shower
observatory is a groundbased observatory
located nearly 4,500 m above sea level
in the mountains of Sichuan province,
China. It has one main objective to find
the highest energy particles in the
universe. The chief scientist on this
mission is Professor Ten Cao who gave
Astramm an exclusive interview about
Lasso's work. He said to make good
measurements for the knee of the cosmic
ray spectrum, you need two things. The
detector must be big enough and it must
be able to identify the original
particle from the air shower it creates.
Cosmic rays become more rare the higher
the energy. For the highest energy
particles, less than one per square
kilometer per century is expected to hit
Earth. To combat this issue, you need
detectors spanning a whole lot more than
a square kilometer, which is why lasso
covers an area the size of 190 football
fields. As for identifying the
particles, I mentioned that the cosmic
rays produce a shower of secondary
particles when they collide with the
atmosphere. And this is what scientists
use. They must essentially piece the
debris together to work out whether the
original particle was a proton, a helium
nucleus, or something heavier. This is a
tricky process as you need to make sure
you catch all the fallout. But Lasso is
one of the most welle equipped
observatories to tackle the challenge.
It has at least three types of
interconnected detectors in an array to
capture the shower and then identify the
original cosmic ray particle. This
unparalleled ability pretty quickly led
to the team's first big discovery.
Professor Cow said, "At the time, we
only had around half of Lasso built. We
put it into operation for around half a
year and suddenly found that there were
so many gamma rays. By 2021, Lasso had
detected gammaray photons with energies
exceeding one pa electron volt or one
quadrillion electron volts. and one at
1.4 quadrillion electron volts, making
it the highest energy photon ever
observed. For context, that's nearly 150
times more energy than the fastest
protons accelerated by the Large Hadron
Collider. Now, the laws of energy
conservation tell us that paelron fault
particles don't just appear out of
nowhere. That colossal amount of energy
has to be transferred to the particles
from a source. Scientists had been
theorizing about such a source for
decades. But Lasso's finding proved its
existence once and for all. The
pevatron.
Pevveratrons are any source capable of
accelerating particles to a paelectron
vault of energy. And their existence
promised to revolutionize the hunt for
cosmic rays. But how do we find them?
Luckily, Lassa wasn't finished. Gamma
rays are useful because they are neutral
in terms of their charge, so they can
travel in straight lines throughout the
universe without being bent by magnetic
fields. This added a new dimension to
Lasso's work. It could trace back to
where the gamma rays had come from.
Mapping these traces across the sky,
scientists identified 12 distinct
sources capable of producing ultra high
energy gamma rays, several of which
showed signs of accelerating particles
to a quadrillion electron volts. There
was a catch, though. Lasso may have
identified the general direction of
these gammaray sources, but scientists
had no idea how far away they were. 12
lines of sight stretching out endlessly
into space isn't exactly a narrow search
field. Except scientists knew something
else about these gamma rays that would
tighten the net. The universe has been
full of photons since the big bang.
[music] And these photons are very cold
with low energies. Gamma rays at ultra
high energies are very likely to collide
with these background photons. And when
they do, they vanish.
This means that gamma rays simply can't
travel vast distances through space. So
if lasso was detecting them here on
Earth, then they couldn't have traveled
very far. In fact, there is no way that
these 12 high energy sources could be
extra galactic. They must be inside our
Milky Way.
Not only did this tell scientists that
the knee, the bend in the graph we saw
earlier, had nothing to do with cosmic
rays coming from outside the Milky Way,
but it brought the search for them much
closer to home. The race was on.
Now, before Lassa's work,
astrophysicists had developed theories
about the production of cosmic rays
[music] and which type of source could
be responsible. After all, space is a
weird and wonderful place, home to
several unusual objects displaying
extreme behavior. But which of these
oddities were capable of producing the
highest energy particles? And how? For
the past 70 years, a popular idea was
that supernova remnants [music] played a
key role in producing cosmic rays. They
certainly have enough energy for it. In
fact, calculations show that if they
converted just 10 to 20% of their
kinetic energy into accelerated
particles, supernova remnants could
supply most of the cosmic rays we see in
our galaxy.
See, when a star goes supernova, it
drives material out into interstellar
space, forming a collisionless shock
wave just ahead of it, where there is a
sharp change in density, magnetic
fields, and pressure. When a particle
hits this shock wave, it gets [music]
bounced back and forth across the shock
front, gaining energy each time.
Particles can propagate here for some
time, up to thousands of years. And the
longer they spend there, the higher the
energy can become. This process is known
as [music] diffusive shock acceleration
or the the mechanism. But although
supernova remnants can accelerate
[music] particles in this way, reaching
pael electronvault energies may still be
tricky. Theoretical models suggest that
supernova remnants are only capable of
accelerating particles to these extremes
during the first 100 years of their life
and all the supernova remnants we know
of are much older.
However, there might be one scenario
where supernova remnants can act as a
source for ultra high energy gamma rays.
If they gain enough energy to overpower
the magnetic forces that confine them,
some accelerated particles may escape
the supernova remnant and get trapped in
nearby giant molecular clouds. Here,
they can interact with the dense gas and
produce gamma rays with energies up to 1
quadrillion electron volts. even if the
supernova remnant itself is no longer
capable of pa electron fault
acceleration.
So supernova remnants show some
potential as cosmic ray producers. Up to
six of the 12 lasso candidates could be
associated with them, but they're not
the main type of source we should be
looking at.
There's another source capable of
creating even higher energies. Pulsars.
We've covered pulsars on the channel
before, so feel free to check out some
of the previous videos for more
information, but as a quick recap,
pulsars are highly magnetized rotating
neutron stars created in supernova
explosions. We have now detected over
1,500 pulsars. But how could they create
such high power gamma rays?
Well, they're already proven to be
capable of accelerating electrons and
posetrons since the dense and highly
magnetized structure rotates to produce
powerful electric fields. These electric
fields can strip electrons from the
stars surface forming a wind of
particles that expands outwards at rapid
speeds. And once this wind reaches the
surrounding material, like the gas or
dust from a nebula, it suddenly slows
down, forming a termination shock. At
this shock point, the particles are
accelerated to extremely high energies.
You can think of it like water flowing
in a stream. Normally, the flow is
smooth, but if you place an obstacle in
the way, some water will spill out, and
this water will be flowing much faster.
The lasso team believed that more than
30% of the candidate feverrons they
detected could be associated with
pulsars, making them a key player in the
search for cosmic rays.
The final type of cosmic ray source came
as a bit of a surprise to scientists. If
we take another look at the spectrum and
zoom [music] into the knee shape, you
see not a smooth line, but a hump. In
other words, an anomaly. The properties
of these cosmic rays didn't fit with
them coming from a known source like a
supernova remnant or a pulsar, which
meant they must have been created by
another type of source. This required
scientists to think outside the box and
propose some other less traditional ways
that particles could be accelerated. And
with that, they recognized what could be
described as nature's ultimate particle
accelerators,
black holes.
The idea that black holes could produce
high energy particles had been discussed
way back in 2009. Named the Bardos silk
west effect after the scientists who
came up with it. It describes a
phenomenon where if two particles move
towards a black hole and collide near
the event horizon, they could reach near
unlimited energies. However, this theory
was thought to be effectively useless
since the particles would no doubt be
sucked into the black hole and lost
forever. That was until more recent
years when newer models revealed that a
fraction of the particles would more
likely be ejected back out into space.
Free of the black hole, these particles
could travel through space as none other
than cosmic rays.
Now, we've discussed some of the theory
behind cosmic rays and where they come
from, but it begs the question, what
have we actually found?
The main thing to understand about this
search is that it's really hard. Lasso
may have identified 12 candidate
Hevatrons in our galaxy, but finding the
actual object responsible is a whole
other task. That aside, the search is
still ongoing, and a few sources have
been found. So, without further ado,
let's take a look.
One of the first objects pinned down may
be familiar to you. The Crab Nebula,
known as Messia 1, it's a supernova
remnant found around 6,500 light-years
away in the constellation Taurus.
Although stunning to look at, Messia 1
is not just a pretty face. It's capable
of accelerating electrons to a
quadrillion electron volts of energy.
And as one of the best studied objects
in the known universe, observing Messia
1 gives astronomers a good insight into
how nature's particle accelerators work.
In the gammaray domain, Messia 1 shows
some extreme variability. It produces
intense flares which can last anywhere
between a few hours to a few days. And
with our new understanding of pevetrons,
scientists realized that these flares
were the photons resulting from some
serious electron acceleration.
Exactly how this happens has been
debated. It could be DSA at the boundary
between the particle wind and the medium
surrounding the pulsar, energy released
by magnetic field lines breaking and
reconnecting, or a more complex
mechanism within the particle wind
itself. For context, electrons at high
energies transfer part of their energy
to background photons, boosting them to
gamma rays that scientists can detect.
However, accelerating electrons is
really difficult because they lose
energy very quickly. To produce gamma
rays with energies of a quadrillion
electron volts, the electrons themselves
must have had several times that energy.
This proves that Messia 1 is undoubtedly
a pevatron and an impressive one at
that. However, this has only been proven
for electrons, making Messia 1 what
scientists call electronic accelerator.
But pevetrons are capable of
accelerating any charged particle. And
if you remember, cosmic rays are mostly
protons. So, it's these pevetrons,
otherwise known as hydronic
accelerators, that scientists are most
keen to find.
I mentioned that lasso detected a photon
at 1.4 peta electron volts, the highest
energy photon ever observed. With such
mindblowing energy, scientists were keen
to see where it came from, which led
them to our next candidate, the Signis
region. The Signis constellation is one
of the most recognizable in the northern
sky, spanning more than 800 square° or
4,000 full moons. And it was here that
scientists found some seriously
interesting stuff. Lasso found lots of
petal electron vault photons inside the
Signis Cocoon, a huge superb bubble
which surrounds a region of massive star
formation. Inside the bubble is a
massive young star cluster known as the
Signis OB2 Association. This is a very
active place and the many young massive
stars can create a strong wind which
accelerates particles. Signis OB2 is
found nearly 5,000 lightyears from Earth
and it lines up pretty well with some of
the gamma rays observed by Lasso. But as
I mentioned, [music] these gamma rays
only indicate the general direction of a
Pevotron, not its distance. [music] So
scientists can often struggle to
identify the origin of a signal among
several possible sources. And in the
case of Signis, [music] there are plenty
of energetic objects to choose from. In
a similar direction to OB2, but further
away, there is an X-ray binary known as
Signis X3.
It consists of a donor star and a
compact object likely a black hole or
neutron star. The donor is a wolf ray
star meaning it is extremely hot and
massive and it feeds material into the
compact object through strong stellar
winds. This combined with the compact
object which releases powerful jets of
plasma creates the perfect conditions
for particle acceleration.
At first, it seemed impossible to tell
which system Lasso was detecting PA
electron volt signals from. But on
taking a closer look at the signal
itself, scientists noticed something
unique. There was a temporal feature of
the signals. A pattern that repeated
every 4.8 hours, seen not just in the
gamma rays, but in the X-rays and the
infrared radiation, too. But where was
the pattern coming from? On further
investigation, scientists realize the
truth. Every 4.8 hours, the black hole
of Signis X3 orbits its massive donor
star. Suddenly, scientists could be
certain the gamma rays were coming from
Signis X3 and that they had found
another Pevverron.
Signis X3 was a particularly intriguing
object. For one thing, the highest
energy photons from this object already
measured 3.7 pal electron volts. And
since photons are radiated by
accelerated protons, the energy of the
proton must be several times larger.
What that suggests is that Signis X3 is
not just a pevetron, but a super
pevetron capable of accelerating protons
to at least 10 pa electron volts.
We've had a whistle stop tour of some of
the most exciting pevatrons we found so
far, but what does the future hold for
this ultra powered search? And where
will it take us? Hunting 12 candidate
Pevatrons seemed hard enough, but since
Lasso's first finding, that number has
boomed. Lasso published the first global
catalog of galactic pevatrons in 2023
detailing 43 ultra high energy gammaray
sources. But now 2 years later and with
[music] continued monitoring from
observatories around the world, the
number of sources has risen to more than
75.
With so many candidate pevatrons hiding
in our Milky Way, we need to seriously
rethink our perception of the galaxy and
what it's capable of. Many thought that
the Milky Way was a relatively peaceful
place since it lacks the massive black
holes typical of galaxies with violent
energetic pasts. However, Lasso's work
has proven this to be an outdated
assumption and is changing the landscape
of our non-therrmal universe. Starting
with our own cosmic home, it's
definitely an exciting time to be
hunting cosmic rays. Lasso is
collaborating with several other
observatories detecting high energy
gamma rays around the world, including
the US, Germany, Namibia, and Spain.
This international network has fostered
an open and collaborative approach to
their experiments, sharing data and
cooperating evidence. Their goal is to
build up a comprehensive spectrum of
photons across different energies as
well as measuring X-rays and gamma rays
above Earth's atmosphere.
I want to give a huge thanks to
Professor Kyle for his expertise on the
world of high energy astrophysics. As
I'm sure you'll agree, studying
pevetrons is a dynamic and rapidly
developing field, and observatories like
Lasso are on the front line. Their work
so far has transformed our galaxy from a
tranquil place to a violent, energetic
mess filled with particle accelerators,
more powerful than anything we can build
here on Earth. We may still be under
attack from cosmic rays, but now we're
ready to [music] chase them back to
their hiding places.
In October 2022, a brilliant flash
pierced the cosmos, brighter and more
intense than anything human civilization
had ever seen. And that's not an
exaggeration. The strength of the blast
blinded our gammaray detectors the world
over and unleashed more energy in a
matter of seconds than our sun will emit
over its entire 9 billionyear lifespan.
Over the 18 months that followed, it
became the most widely studied gammaray
burst in history. Creatively dubbed the
boat for the brightest of all time. As
researchers began to decipher its cause,
their findings unraveled one mystery
after another. Scientists have been
cataloging gammaray burst for decades.
But this one was closer, brighter, and
unexplainably devoid of some key
signatures you'd expect to see. It also
raises some farreaching questions about
our standard model, the possibility of a
dark matter particle, and how heavy
elements like gold are made.
I'm Alex Mccoan, and you're watching
Astramm. Join me today as we dive into
the mystery of the biggest and brightest
gammaray burst of all time. What caused
such a colossal explosion? How is it
different from other gammaray bursts
before it? And what can it teach us
about our understanding of the universe
and the particles that constitute it?
Gammaray bursts are brief intense
flashes of high energy gamma radiation
lasting from milliseconds to several
minutes. [music] The first of its kind
was detected in 1967 when American
satellites designed for detecting covert
Soviet nuclear testing picked up an
unusual pattern of electromagnetic
energy. Since then, gammaray bursts have
been of tremendous interest to the
cosmological community as they allow
scientists to study states of matter and
physics that are not reproducible on
Earth. Essentially, they provide
researchers with a glimpse of how stars
are formed and evolve across the whole
timeline of the universe.
There are two different kinds of
gammaray bursts. Short gammaray bursts
last less than 2 seconds and are
attributed to either the collision of
two neutron stars or the merger of a
neutron star and a black hole. They can
be followed by a kilonova, an emission
of bright light resulting from the
radioactive decay of chemical elements.
This decay creates even heavier
elements, an important feature of nove
which we'll discuss more later. Anything
lasting longer than 2 seconds is classed
as a long gammaray burst. These are
thought to be caused by the explosive
deaths of massive stars and their
subsequent supernova. The collapsed core
may form either a neutron star or a
black hole. These typically occur close
to the edges of the observable universe
because they are characteristic of low
metalicity stars which formed when there
were less heavy elements around. When we
see one of these, we are witnessing
events from billions of years ago. In
the case of both long and short gammaray
bursts, the newly formed black hole
blasts out jets [music] in opposing
directions containing particles
accelerated close to the speed of light.
When these particles interact with
surrounding matter, they emit the gamma
rays we detect. So, what made the boat
so special? Let's start by analyzing
some of its key characteristics.
Firstly, the boat lasted 10 whole
minutes and was detectable for 10 hours
after the fact. It occurred in the
Sajitta constellation only 2 billion
lighty years away, which is much closer
than other gammaray bursts we've
detected until now. In fact, such a
bright explosion so close to Earth is
thought to be a 1 in 10,000year event,
meaning the last time one happened,
humans had barely started farming. As is
the case with other long gammaray
bursts, we know a collapsing and
exploding star was behind it. But this
is where things start to get fuzzy.
A supernova alone isn't enough to
explain the magnitude of the gamma rays
emitted.
The boat was a whopping 70 times
stronger than any other gammaray burst
detected. Initially, the theory was that
this must be the supernova of a
ginormous star the likes of which we
rarely see. However, upon closer
inspection of the afterglow, scientists
found that the supernova behind the boat
was shockingly ordinary. [music]
To get a clearer picture, astronomers
pointed the James Webb Space Telescope
in the boat's direction. Web's near
infrared spectrograph revealed that the
supernova behind the boat was actually
pretty average. It wasn't nearly as
bright as you'd expect given the
gammaray burst that accompanied it. So
what could have caused such a flash?
One idea is that we simply perceive the
flash as bigger and brighter because of
Earth's relative position to the blast.
Imagine a flashlight shining in the
dark, diffused and soft. It lights the
path 1 to 2 m ahead of you. Now imagine
capturing all that light and focusing it
into a singular laser beam. It wouldn't
illuminate the path as widely, but it
would reach hundreds of meters into the
distance. And if Earth was in the direct
path of that laser, it would register a
super bright reading. That doesn't mean
the laser released more energy than the
flashlight. It just means the way it was
concentrated and then detected resulted
in a higher reading. The same concept
can be applied to these gammaray bursts.
If a massive star is spinning super fast
when it collapses, then the shape and
structure of the near lighteed jets it
emits will be more narrow and focused
and therefore brighter. In fact, the
jets seen from the boat are some of the
narrowest we've ever seen.
But not only were these particle jets
brighter than expected, scientists also
detected way more of them going faster
than expected, [music] they traveled
with such fervor that after 2 billion
years traversing the cosmos, they
arrived here and momentarily disrupted
the Earth's atmosphere.
Sitting just 50 to a,000 km above the
surface of our planet, Earth's
ionosphere is rich in electrically
charged particles. When the boat struck,
it left a mark comparable to that of a
major solar flare, pushing the
ionosphere down into lower altitudes. If
photons from an explosion 2 billion
light years away can have this kind of
effect on our planet, I don't really
want to think about what happens if
something like that in our neighborhood
explodes.
The large highaltitude air shower
observatory in Daqeng County, China,
managed to capture data on tens of
thousands of photons over the course of
the initial blast and into the
afterglow. This is a quantity unlike
anything seen before in gammaray
astronomy. In fact, it's so far out of
pocket that some astrophysicists think
that they might be pointing towards
something missing from our models.
According to our current understanding,
it's very unlikely these super high
energergy photons are traveling for two
billion years. Cosmic microwave
background radiation, interactions with
intergalactic dust, or redshifting
caused by the expansion of the universe
are all factors that can interfere with
a photon's trajectory. One hypothesis
put forward is that photons convert
themselves into a hypothetical particle
called an axion and then convert back
into gamma rays upon reaching our
galaxy's magnetic field. Axons are
thought to be an ultra light particle
responsible for dark matter. Their
existence is currently purely
hypothetical. We have no evidence for
them. And even if we did, they would lie
outside the standard model of particle
physics. We don't have time to delve
into detail in today's video, but let me
know if you'd enjoy a separate video on
this in the comments.
Okay, so far we've established that boat
was caused by a massive star collapsing
and turning into a black hole, which
incidentally is known as a collapsar.
Aside from generating a long gammaray
burst, collaps are also known for
generating something else. Gold.
Wait, wait. How is gold connected to
gamma rays? Good question. To understand
[music] that, let's take a minute to
discuss how elements are made.
The core of a star is a super high
pressure environment, some 200 billion
times higher than the atmospheric
pressure on Earth. In these conditions,
nuclear fusion reactions create heavier
elements out of lighter ones. For
example, one helium atom comes from
fusing four hydrogen atoms together.
Elements 2 through 26 on the periodic
table, that's helium to iron, are made
this way. The process known as stellar
nucleioynthesis.
However, once you get to iron, it isn't
energetically favorable to continue
making bigger and bigger elements this
way. So, how do we account for the rest
of the periodic table? Where do these
heavier elements like gold come from?
[music]
At the moment, we know two different
ways these elements are formed. The
first was recently confirmed by the
James Webb Space Telescope. When two
ultra dense neutron stars collide, they
emit an immense amount of neutron
particles. Surrounding material captures
these neutrons, making their atoms
temporarily unstable. In order to
stabilize, the neutrons undergo
radioactive decay into protons, creating
new, heavier elements. This process is
known as rapid neutron capture or R
processed nucleiosynthesis.
Some calculations suggest one neutron
star collision can produce up to three
Earth masses worth of heavy elements.
However, this explanation alone isn't
sufficient to account for all the heavy
elements in the universe. Neutron star
collisions are rare and take a long time
to happen in the order of billions of
years. On top of that, observations of
very old stars show that heavy elements
were already present in parts of the
universe well before most binary neutron
stars would have had a chance to
collide. So, how do you explain that?
There must be another source of heavy
elements in the cosmos. Which brings us
back to our boat.
>> [music]
>> There's another theory that collaps like
the boat could be another source of our
process nucleioynthesis.
In their dying stages, massive stars
like the one that caused the boat are
surrounded by layers of exploding gas.
These explosions leave discs of matter
swirling around the resulting infant
black hole. As the black hole begins
devouring the surrounding material, it
can only ingest so much at a time. What
it cannot manage is swept away in a
neutron dense wind. Here the same R
process nucleiosynthesis occurs forming
heavier elements like gold, silver, and
platinum. This seems promising, but
unfortunately even factoring in these
kinds of supernova isn't enough to
account for the abundance of gold in the
universe.
To make matters worse, analysis of the
boat spectrum didn't show any traces of
heavy elements, raising questions about
the validity of this collapsar gold
making theory. Some scientists suggest
the boat's host galaxy might have
something to do with the lack of heavy
elements in the explosion. Upon modeling
the host galaxy spectrum, researchers
discovered it has the lowest metallicity
of all previous host galaxies where
gammaray bursts were detected. In other
words, maybe the environment didn't have
the right building blocks to make
heavier elements. How do we know how
much gold should be out there in the
first place? How do scientists predict
something like the relative abundance of
elements in the universe?
There are two main methods of
calculating this. The spectroscopy of
stellar photospheres and meteorite
analysis. By analyzing the absorption
lines in the spectra of stars,
astronomers can determine the relative
abundances of elements in the
photosphere of those stars. The
composition of meteorites, remnants of
an early solar system, are analyzed in
parallel to determine the relative
abundances of elements. Meteorites are
especially useful for measuring the
abundances of volatile elements like
hydrogen, helium, and noble gases that
are unrepresented in stellar
photospheres. The results of both of
these methods are usually congruent,
indicating we're probably doing
something right. But this is physics, so
of course nothing is so cut and dry. One
famous exception to this rule is
lithium. According to the standard big
bang nucleiosynthesis theory, the early
universe should have produced about
three times more lithium 7 than is
currently observed. The plot thickens
when we consider its isotope, lithium 6,
where we observe 1,000 times more than
our predictions can account for. This
discrepancy is known as the lithium
problem and remains unsolved, presenting
a significant challenge to the standard
cosmological model. It highlights the
importance of understanding the
processes that shape the relative
abundances of elements in the universe
and suggests that our current
understanding of nucleiosynthesis might
be incomplete.
Just because boat didn't yield gold as
expected doesn't mean we should discard
these kinds of extreme gammaray bursts
as places where heavy elements could be
made. Observations of nearby stars have
provided strong evidence for an early R
process that enriched the universe with
heavy elements. But the boat findings
cannot be ignored as they suggest there
may be alternative currently unknown
processes responsible for this elemental
enrichment of our cosmos. The results
may call into question our entire model
of understanding regarding collapse
stars and their role in creating heavy
elements. This discovery is much bigger
than just the boat or gamma rays. It's
about the literal building blocks of our
universe as we know it. Where do our
different atoms come from? And why do
they exist in the proportions they do?
How much of our model is accurate and
how much is missing? What role does dark
matter play in all of this? We need more
time and research before we know for
sure. But the boat is a great example of
how new findings keep our understanding
of physics ever evolving, just like the
universe itself.
When the James Web Space Telescope
finally saw the edges of the universe,
we knew we had a problem. [music]
Web was able to resolve light emitted
from stars 13 billion years ago, helping
us to peer back in time to some of the
universe's earliest moments. But what we
saw was not a sparsely populated proto
universe where matter was only just
starting to coalesce into the first tiny
intermittent galaxies here and there.
The early universe was a bustling place.
It had galaxies,
too many of them. They were too bright.
And the black holes we started to spot
in their hearts had grown too big too
quickly.
Some began to proclaim that our models
were wrong and cosmology was in crisis.
And while some of these problems have
begun to alleviate as better data came
in, other problems simply became more
prominent. But in a strange twist, one
of the most resilient mysteries in all
of this might be about to unravel thanks
to a black hole with an impossibly big
appetite.
Its name is lid 568
and we've just seen it breaking the
Edington limit consuming matter faster
than it should be able to and it might
just be the key to everything.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we explore lid
568, the Edington limit, and its
groundbreaking implications on
cosmology.
A black hole breaking physics. By now, I
really shouldn't be surprised.
It takes time to up a galaxy.
Interstellar gas [music] and dust need
time to subtly come together under
gravity until a critical mass is reached
and [music] stars begin to ignite. These
stars live and die and from their
deaths, new stars are formed. This too
takes time. Cosmologists have observed
our universe and [music] based on what
they saw created models for how old our
universe is and how quickly galaxies
form. which is [music] why the James
Webb Space Telescope data caused such a
crisis. Things were not as the models
predicted. [music]
Fortunately, some of those problems
proved solvable in the months after the
data was released. For example, the
brightness of the galaxies we could see
through web. This brightness implied
that there were far too many stars
present in those galaxies. So many stars
should have taken much longer to form.
And yet there they were, fuzzy red dots
at the edge of Web's resolution.
However, scientists at the University of
Texas studying Web's cosmic evolution
early release survey realized there
could be another explanation for all
that excess [music] light. And
counterintuitively,
that explanation was black holes.
If we work under the assumption that
there were massive black holes in these
galaxies rapidly consuming cosmic gas,
then the intense friction given off by
these hungry leviathans as they ate
created an excess of light in their
accretion discs. This explains why
galaxies overall seemed brighter and
were throwing off our estimates. Once
you add these shining black holes, you
don't need so many stars. The mass of
each problematic galaxy dropped and
everything fell back into line with the
cosmological model. Problem solved.
This reinforced how important black
holes are to our understanding of the
early universe, which was in and of
itself a problem because the black holes
themselves broke our models, too. In
particular, cosmologists struggled with
the thorny question of how they'd come
to be.
For small black holes known as stellar
black holes, there was no issue. Stella
black holes have masses a few to 100
times that of our sun. And we understand
very well how they are formed.
They are the collapsed remnants of a
sufficiently massive star and there
would have been time for such black
holes to form in the early universe. But
scientists were struggling with the
super massive black holes with masses
tens of thousands to billions of times
that of our sun which tend to lurk at
the central point of galaxies and due to
something called the Edington limit.
There just shouldn't have been time for
these kinds of black holes to have
formed where and when webb saw them. And
yet there they were and they were
numerous.
Stella black holes can grow as time goes
on, provided you funnel more mass into
them. But how quickly?
In 1920, an English astronomer and
physicist called Arthur Edington
formulated the idea that there was a
limit to how quickly either a star or a
black hole could grow. This was because
photons carry momentum. A tiny amount,
true, but enough to exert a push. This
is what pushes [music] solar sails on
certain hypothetical spaceship designs.
That tiny amount of momentum imparted by
photons.
For mass to enter into a star, it has to
push against a constant stream of
photons that are radiating outward. And
at a certain level of brightness, not
even gravity is strong enough to pull
against the flow. This is called the
Edington limit. and stars that brush
against its boundaries, such as Volraier
stars. Bright stars at least 20 times
more massive than the sun, emanating
powerful stellar winds, are just the
slightest nudge away from blowing
themselves apart. For black holes, you
might think this would be less of a
problem. Isn't the whole point of black
holes that they don't radiate any light?
But their accretion discs are a
different story. As we discussed
earlier, accretion discs [music] around
super massive black holes can be
incredibly bright, particularly around
super massive black holes, sometimes
dwarfing the brightness of the stars in
[music] the galaxy they reside in. With
brightness comes resistance to gravity,
and black holes have to obey the
Edington limit, too.
So even though given enough time and
mass, stellar black holes could
theoretically [music] grow into super
massive black holes, it doesn't seem
plausible that this actually explains
all the super massive black holes we see
in the early universe. simulations have
been run and although it is technically
possible to grow a stellar black hole
into a super massive black hole in that
time frame, it would require those black
holes to be feeding at near the Edington
limit nonstop since their birth, which
just doesn't happen. Black holes in real
life often run out of mass nearby and
need to wait to run into more or for
more to come to them. To further
complicate the matter, we're not
completely sure that super massive black
holes are the grown-up version of
stellar black [music] holes in the first
place. Although it seems like common
sense to assume so, scientists have been
confused at the lack of the intermediate
stage of black holes observable in our
universe. To be frank, they've not cited
any, at least none for sure.
Super massive black holes are common at
the center of galaxies and there are
thought to be 100 million stellar black
holes in our Milky Way alone based on
the number we've seen. But intermediate
black holes are suspiciously lacking
with only a handful of potential
candidates. You would think we'd see a
lot more.
Struggling for certainty, scientists
began to hypothesize that super massive
black holes were instead born in some
other way. Many cosmologists have been
exploring the idea that because
everything was much closer together in
an early universe, things might have
been dense enough that interstellar dust
itself could conceivably have collapsed
to form a black hole directly, skipping
the star step altogether. If this is
true, and there is some evidence to
support the theory, then perhaps super
massive black holes were once capable of
simply being born that size or near it
right from the offset, even if such a
thing is no longer possible in our more
spread out universe today. But this is
by no means certain. But then lid 568
came onto the scene and the pendulum
swung the other way again.
Lid 568 [music]
is a very distant black hole between
12.1 and 12.3 billion lightyears away.
It's so far away from us that we can't
see it at all using visible light. The
expansion of the universe has redshifted
it all into infrared ranges. But even
its infrared emissions were too dim to
be picked up by heavy hitters like
Hubble alone. It took the Chandra Cosmos
Legacy Surveys combined telescopes and
the incredible resolution of the James
Web Space Telescope to see it at all.
Even then, LID 568's whole galaxy is a
little more than a faint red and compact
dot. But the light emissions from this
[music] red dot are revealing.
X-rays given off by lid 568's accretion
disc reveal that it was actively
consuming matter in its galaxy's heart
in a way that no one expected.
You see, LID 568 crucially breaks the
[music] Edington limit. And not just by
a little, it's 40 times over the
accretion speed limit. It's well on its
way to having its license revoked. How
is this possible?
It turns out that breaking the Edington
limit is in fact possible, but only for
short bursts or in sneaky ways. For
example, jets can help you get around
the Edington limit. If all your photons
are being blasted off in a single
concentrated direction, all the other
directions can eat to their heart's
content with no photon feedback getting
in the way of a good meal. There are
other possibilities. While Edington's
limit says that once the brightness of
the accretion disc becomes too high, all
the black holes food will be blown away.
There is a period of time before this
happens where a greedy black hole can
snatch at the escaping matter and
potentially enter super Edington
territory. like an overeager diner, it
might pay for it later, but for a short
burst, that level of accretion can
occur.
If this is true, it might just explain
how super massive black holes in the
early universe came to exist. And
certainly, LID 568 exists and is the
clearest example to date of a black hole
accreting this quickly. that demands our
consideration. Much like the impossible
super massive black holes themselves,
they are there. It's now our job to
attempt to understand how that's
possible.
So, mysteries remain. If lid 568 is
increasing matter past the Edington
limit, it proves such a thing is
possible. But what of the other strange
things Web saw? Where are the
intermediate black holes that stellar
black holes ought to grow into on their
way to becoming super massive? Why are
there so many galaxies in the early
universe more than our model should
allow? Do direct [music] collapse black
holes, ones form from the cosmic dust
itself with no stellar intervening step,
really exist?
Our models might be on the right track,
but something is missing or incomplete.
Black holes exert a phenomenal influence
on our universe, and there are secrets
surrounding them that they guard
jealously.
But as powerful as the James Web Space
Telescope is, it has [music] not allowed
us to crack this mystery. Not yet. But
then perhaps we ought to be pacing
ourselves. Thanks to our telescopes, we
have seen billions of trillions of stars
and that's a lot of data. Accrete too
much information all at once and it
might prove difficult to absorb it all.
So says Edington and his rule is never
to be broken except of course when it
is.
We often think of black holes as
destroyers. They suck everything within
their reach into them and give nothing
back. They are the end, the final
destruction of the universe. And yet,
what if I said to you that they might
actually prove to be our salvation?
Black holes might provide the answer to
traveling faster than the speed of light
and solving the energy crisis in ways we
couldn't have even imagined until
recently.
And as by now I have come to expect,
they do so by messing with the fabric of
reality itself and by completely
countering my expectations of physics.
[music]
Perhaps we have been thinking about
black holes all wrong.
I'm Alex Mccoan and you're watching
Astramm. Join me again for the fifth
video in my series about black holes,
where once again my mind has been blown
by the incredible potential and
implications of these very real objects
in our universe.
I've talked before about the formation
of black holes in this series, including
aspects about their event horizons,
how they are created,
and how they might possibly end.
But to understand how a black hole
ignores the usual limitations on faster
than light travel and does so in a way
that you can benefit from it without
having to go inside a black holes event
horizon and how it produces near
limitless energy at the same time then
we are going to have to understand more
about the features of black holes than
we've covered so far. So, a quick recap.
What is a black hole? In its simplest
form, a black hole is an object in space
that is so massive and so dense that the
gravity it creates is too powerful for
anything to escape it. We are familiar
with the iconic black spherical zone
that surrounds a black hole. This is the
black hole's event horizon. This sphere
is the demarcation point between
escapable gravity and inescapable
gravity.
Because the gravitational pull increases
the closer you get to a black hole. Once
you go beyond the event horizon,
nothing, not even light, can travel fast
enough to get away again. Beyond that,
though, it's actually quite difficult to
say much about the black hole's features
at all. Precisely because of the event
horizon, we cannot see what the inside
of a black hole looks like. In fact,
there are only three things we can say
about black holes with any degree of
certainty. They have mass, they have
charge, and they have angular momentum.
You might wonder how we know these
things about black holes given that no
light can leave them to tell us about
them. The key to these three
characteristics is that all three of
them represent aspects of the black hole
that can be felt outside the black holes
event horizon. Charge, for instance,
works the same way around a black hole
as it does around any other charged
object. That is to say, if a black hole
is charged, then it will attract objects
that have different charge to it and
repel objects that share its charge.
Think of it like a giant magnet pushing
and pulling on the universe around it.
Scientists can track objects that
approach a black hole and by seeing how
quickly certain objects known to have a
charge move towards it, scientists can
predict the charge of the black hole
itself.
Interplaying with this is mass.
The mass of a black hole can also be
felt outside the sphere of the event
horizon. In fact, it is the main creator
of the event horizon in the first place.
This is because mass creates gravity and
does so in a linear fashion in
accordance with the same principles you
might find in Gor's law, a theorem about
electromagnetism,
albeit with a gravitational analog.
So, it's possible too to calculate the
mass of an object by seeing how far away
objects are before they start to
accelerate towards it and how quickly
they accelerate. Although obviously you
need to factor in charge at the same
time or your results might get skewed.
Finally, angular momentum or spin. It is
possible to detect the spin of a large
mass object and we are going to dive
into the how in just a bit. For now,
let's just accept it as a given and
recognize that black holes are certainly
very high mass objects.
There are varying sizes of black holes
in existence. The smallest known as
micro black holes have a mass that's
comparable to that of our moon or 7.35 *
10 ^ 22 kg.
They fit all this into a space that's
just 0.2 2 mm in diameter, which is
incredible. It really gives you a sense
of how dense a black hole can be.
Something thinner in size than a human
hair, packing the mass of the moon. And
that's just the smallest ones. Stellar
black holes have a mass equal to 10
times our sun and have a diameter equal
to 60 km. Intermediate black holes are
the mass of 1,000 suns and fit all of
that into a diameter of 2,000 km, which
is still much smaller than the Earth. It
is the largest black holes that really
dwarf us with masses between 100,000 to
10 billion times the mass of the sun and
sizes ranging from 0.001
to 400 astronomical units. an
astronomical unit being the distance
from the Earth to the Sun.
But other than those three features,
there are in theory no other differences
between them. If you put two black holes
in the same room and made sure they had
the same mass, charge, and spin, it
would be impossible to tell them apart.
However, these three features are enough
to have some interesting effects on the
area of space outside a black hole.
Traveling inside a black hole is
impossible. Space and time break down
past the event horizon. But we think we
know a few things that must exist inside
one. Beating in the heart of a black
hole, there is thought to lie the
singularity. In truth, this actually is
the black hole. When we were discussing
diameters earlier, that is just the
diameter of the event horizon. Again, we
are not certain what a black hole
actually looks like because light can
never escape it. In a space that is
infinitely small, there is a point where
all the mass of the black hole is packed
so that it is infinitely dense. For the
simplest models of black holes, the ones
that do not spin, this is a single
point. In a rotating black hole, this is
more like a little spinning ring.
Otherwise, it would be difficult to
define spin for a point that has no
volume. Our
current physics get very strange around
such a black hole. If ideal paths are
traveled around this point, it becomes
mathematically possible to do some very
strange things like meet up with your
own past. This has some disturbing
implications for causality and gets into
time travel paradoxes like the
grandfather paradox. So that probably
only shows for certain that our ideas
about singularities are not quite right
yet. Because the singularity is so
small, it'll take the successful merging
of quantum theory and general relativity
theory to properly explain what is going
on inside a black hole. And we have not
yet managed to do this. It may one day
turn out that singularities do not exist
in the hearts of black holes at all. But
this is the extent of our knowledge so
far.
Well, whatever it is that lies inside a
black hole, it powers our faster than
light engine because like most objects
in the universe, it spins. And oh, does
it spin.
As we travel out from the center of the
black hole, we pass through the event
horizon with little fanfare. The event
horizon actually cannot be detected
locally, although a person outside the
black hole might watch you slow down to
a complete stop as you travel through
it. From your perspective, it actually
might seem like time is flowing
normally. Normally, that is until the
universe outside the black hole runs its
course in an [music] instant because
time outside the black hole is traveling
so fast compared to you. This is the
essence of relativity and we talk about
it in another of my videos which you can
look at here.
In fact, the only evidence you might
have that you've passed the event
horizon at all is because of something
that exists just outside it, the photon
sphere.
In a zone just outside the event
horizon, there exists a point in [music]
space where if a photon enters it at
just the right angle, it will enter a
perfect orbit around the black hole in
much the same way the moon perfectly
orbits the Earth. This infiniteesimally
thin zone is known as the photon sphere.
And given the number of photons that
have flown past black holes in all the
millions of years they have existed, it
is probably filled with photons. It is
quite possible that you would be
instantly fried as you pass through this
point.
However, it is just outside here that we
find the zone that interests us, the
ergosphere.
This is the zone around a black hole
where we can most easily detect its
spin. And this is because in this zone,
it is impossible for us not to move. You
see, mass affects space. We see this in
the curving effect of gravity on the
travel of objects through that region of
space. However, it might be more
accurate to say that mass drags on the
space around it. As it moves through
space, it brings a little bit of that
space along with it for the ride. And
when an object as massive as a black
hole spins, there is an effect known as
frame dragging. To put it simply,
reality around the black hole begins to
spin in a whirlpool that cannot be
fought against. Much like a real
whirlpool, anything caught within the
ergosphere is spun around the black hole
because the frame of reference it sits
in is being pulled.
Sort of like how a person moves because
they are standing on a moving walkway.
The greater the spin of the massive
object, the faster this happens. And in
the ergosphere, this can occur at a
speed so fast that by the event horizon,
space is moving faster than the speed of
light. You would need to travel faster
than the speed of light in the opposite
direction just to stay at a relative
standstill from the point of view of the
outside observer, which of course you
cannot do.
But isn't this against the laws of
physics? Doesn't Einstein say that
nothing can travel faster than the speed
of light? The answer to that is yes. But
black holes have found an interesting
loophole. You see, this rule only
applies locally. Right where you are in
your frame of reference, nothing can go
faster than the speed of light. But
thanks to relativity, it is possible for
frames of reference to move away from
each other so fast that objects in them
appear to be breaking this light barrier
from your point of view.
But if you move next to them and entered
their frame of reference, they would
seem to slow down and would start
obeying the laws of physics again.
It's a really weird effect, but frame
dragging is an actual thing. It is by
measuring frame dragging that scientists
can learn the spin of a black hole.
However, according to a man called Roger
Penrose, there may even be a way of
exploiting it. If you were to send a
rocket into this section of the
ergosphere, the rocket would speed up
due to being caught in the whirlpool of
reality. Once it had gained enough
speed, it could then fire a propellant
in such a direction that it pushed
itself out of the whirlpool again, but
now traveling at a much faster speed.
This method, named the Penrose process,
could hypothetically net you energy
equal to about 20% of the mass of your
rocket. Now that might not sound like
much, but remember according to
Einstein's E= MC^², your 20% mass would
produce energy equal to itself times by
299,792,458
squared. That's a lot of energy.
So to harness this colossal kinetic
energy, all you would need to do is
travel to the nearest black hole, which
is roughly 3,000 lightyears from us, and
enter its ergosphere with a rocket
capable of surviving the intense
gravitational forces there. Ideally, you
would need to find one that was not
surrounded by an accretion disc because
those get up to temperatures of millions
of degrees, as they are swung around at
near light speeds and melt from solids
down to gas and plasma. But you get the
idea. Easy.
Okay, maybe this is a little impractical
for us, but the implications for faster
than light travel that black holes
demonstrate through frame dragging might
just offer us the key to one day beat
the light barrier for real. Not by going
faster than light ourselves, but by
somehow convincing the frame of
reference we are in to travel at those
faster speeds, just like they do around
a black hole. Of course, if this
requires the energy of a black hole to
accomplish, we might be out of luck for
now, but it's an incredible glimpse into
what is possible, and scientists are
already looking into the power of frame
dragging for future travel. But maybe
that's a topic for another video.
Either way, this all just highlights
once again how our universe really is
very different from what we might have
ever imagined.
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