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.
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 hole's 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 a 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. Before we get
in the description below. Go check them out. Now, let's get back to black holes.
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 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 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 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= MC², 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 lighty years 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.
If you're a longtime viewer of Astramm,
you'll already know that Beetlejuice is
no ordinary star. Beetlejuice is a red
super giant in the Orion constellation
that's just 650 light years away from
the solar system, making it the second
largest and 10th brightest star in the
sky, not counting the sun. A few years
ago, Beetlejuice made headlines when the
bright super giant appeared to be
getting dimmer, indicating that it might
be about to explode in a supernova.
But that wasn't the only surprise that
Beetlejuice had in store for
astronomers.
Measurements from the Elmer Array of
telescopes have detected that
Beetlejuice is rotating at a mindbending
rate of well, just about once every 20
years. Okay, that might sound a little
underwhelming, but for a star the size
of Beetlejuice, this means that the
surface is spinning at a speed of 18,000
km hour, or about 5 km/ second. That's
10 times faster than our own velocity on
the surface of Earth. And for a massive
super giant star, it all but breaks the
laws of physics.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we dig into
the unusual surface of Beetlejuice and
the secrets behind its seemingly
impossible rotational speed.
Let's start with the basics. There are a
couple of different ways to measure the
rotation of objects in the night sky. If
the object is big enough, like the sun,
the moon, or even a planet in our solar
system, it's easy enough to point a
telescope at it and watch its features
move in real time. For reference, the
angular diameter of the moon is about
half a degree, and you can probably make
out its features with your own eyes.
Jupiter's angular diameter comes in at
100th of a degree, but its features are
still clearly visible through a
telescope. So, what about Beetlejuice?
The super giant star just 650 lighty
years away. For all its size,
Beetlejuice is still far enough away
from Earth that its angular diameter is
1,000 times smaller than Jupiter's,
making it look like a total blur to even
our most powerful telescopes.
Luckily, there's another way to tell
whether a star like Beetlejuice is
rotating. It's less direct than just
well looking at it, but it's an
ingenious technique that relies on a
simple effect you might have already
heard of, Doppler shift. The same effect
is also responsible for the change in
pitch from a siren as an ambulance
passes by. When the ambulance is moving
towards you, the siren sounds higher
pitched because the sound waves hit you
at a higher frequency than if the
ambulance were standing still. But as
soon as the ambulance starts moving away
from you, the effect reverses. Sound
waves hit you at the lower frequency and
the siren sounds lower pitched. What you
probably wouldn't notice is that the
Doppler shift affects light waves
bouncing off the ambulance just like it
affects the sound waves coming from its
siren. The higher frequency light as the
ambulance approaches makes it look ever
so slightly bluer. And as soon as it
starts moving away from you, the effect
flips and it looks ever so slightly
redder. The only reason this visual
effect isn't obvious is because the
speed of light is a million times faster
than the speed of sound. So, it would
take a much faster ambulance for us to
actually notice the optical Doppler
shift.
We might not have ambulances here on
Earth flying by 5 km/s, but those kind
of speeds are fair game out in space.
Which brings us back to Beetlejuice.
When a star is rotating, half of its
surface will be moving towards us while
at the same time the other half will be
moving away. This creates a gradient of
colors emitted by the star that we can
observe with our telescopes. Even if the
star is too blurry for us to make out
any of its distinct features, by seeing
which side is bluer and which side is
redder, we can infer the direction of
rotation. And by measuring how different
the bluer frequencies are from the
redder ones, we can calculate the stars
rotational velocity. This was the
technique used by astronomers to analyze
the data collected by Alma and conclude
that the surface of Beetlejuice was
spinning at 5 km/s.
That's all well and good except the
known physics of spinning stars predicts
that 5 km/s is far too large a velocity
for a red super giant like Beetlejuice.
Take our sun as an example. Its
rotational speed is in the same ballpark
around 2 km/s but it's also 1,000 times
smaller and about 10 times lighter than
Beetlejuice. If our sun expanded to the
size of Beetlejuice, which would envelop
the entire inner solar system and nearly
reach Jupiter's orbit in the process,
then its velocity would drop to just 2
m/s
in order to conserve angular momentum.
In the same way that a spinning ice
skater slows down when she spreads out
her arms, and if the sun grew 10 times
heavier to match the mass of
Beetlejuice, its velocity would drop to
0.2 2 m/s.
So, the larger and heavier a star is,
the slower we expect it to spin. And
yet, Beetlejuice appears to defy all of
those expectations.
What's going on here?
One possible explanation is that even
though Beetlejuice didn't start out with
this much angular momentum, it gained it
through a process known as stellar
cannibalism. As you might expect,
stellar cannibalism is just what we call
it when one star eats another star,
usually its companion in a binary orbit.
In more scientific terms, the stars
gravity pulls away its companion's gas
layer by layer until only the inner core
remains. That gas carries most of the
companion stars angular momentum. So,
the first star ends up not only growing
larger, but also spinning faster than
nature would normally allow. But is this
really the story of how Beetlejuice got
its spin? Or is there something even
more mysterious happening under the
surface?
A team of researchers collaborating
across Europe and China have recently
suggested that Beetlejuice's apparently
ludicrous rotation speed might just be a
giant optical illusion.
To see how that's possible, let's think
back to what the team at ALMA really
measured with their state-of-the-art
array of telescopes. Though their
pictures of Beetlejuice were blurry,
they were still able to make out that
one half of the star emits slightly
redder frequencies of light than normal,
while the other half emits slightly
bluer frequencies. The obvious
explanation for this 50/50 split is that
the star is rotating with one half
moving towards us and the other half
moving away from us at the same time.
The green arrow in the image of
Beetlejuice is meant to represent the
axis of this rotation. But what if
that's not the only explanation for the
color gradient detected by Alma?
Simulations of Beetlejuice have revealed
that its surface is a chaotic, turbulent
place, constantly bubbling under its own
heat like water bubbling in an oven.
Each of these bubbles is enormous and
propagates outwards at deadly
velocities. A single bubble can be 100
million km across, covering a large
fraction of the surface of Beetlejuice.
And if one of these bubbles were headed
your way, even today's most powerful
spacecraft wouldn't save you from its
lightning fast speed of up to 30 km/s.
Your only hope would be for the bubble
to pop and crash violently back down
onto the surface before it ever reaches
you. As gas bubbles all over Beetlejuice
rise and fall, its surface becomes a
mosaic of regions that are either moving
towards us or away from us. as observers
on Earth. In turn, the Doppler shift
causes light emitted from these regions
to be either blueshifted or redshifted.
In a recent paper that rose to challenge
all previous explanations of
Beetlejuice's rotation, the
International team of researchers
proposed that Beetlejuice might not be
rotating fast at all. Instead, the Elma
observations might be detecting a range
of light frequencies coming from
Beetlejuice due to the turbulence on its
surface. Thus, astronomers may have been
misinterpreting those shifts in
frequency as rotational effect. But if
you've been paying close attention to
the physics, you might have noticed that
there's still a loose end with this
alternative explanation. A rotating star
should produce a smooth gradient of
light frequencies, ranging from bluer
than expected light on one edge to
redder than expected light on the other.
Meanwhile, a turbulent star should
produce a random patchwork of colors
with bluer patches where bubbles happen
to be rising and redder patches where
bubbles happen to be falling back down.
How could the astronomers at ALMA
possibly have mistaken one for the
other? If astronomers observed a smooth
gradient of colors coming from
Beetlejuice, shouldn't the patchwork
explanation already be ruled out?
In an ideal world, that would be true.
Gradients would correspond to rotation
and patches would correspond to bubbles.
But remember that Beetlejuice is so far
away that the image captured by Alma is
far from ideal. And it's more of a blur
than an HD photograph. When simulations
of the surface of Beetlejuice are made
to account for the limited resolution of
observations, they predict that the
bubbly patches of red shift and blue
shift will be easily mistaken for a
rotational gradient about 90% of the
time. This means that even if the
astronomers at ALMA did nothing wrong in
their analysis, they may have been
fooled by Beetlejuice's boiling surface
into thinking it's spinning way faster
than it actually is. This also means
that astronomers are now chasing after
one key objective. Higher resolution
studies of Beetlejuice that could more
accurately tell the two scenarios apart.
The good news is that better images of
Beetlejuice already exist, taken by the
same telescope, but with longer exposure
times. The bad news for those of us who
are more impatient is that it will
likely take a couple of years for them
to be properly analyzed. Those answers
are coming though. For now, I'm curious
to know where you would place your bets.
Is Beetlejuice really spinning at 5 km/s
after having eaten its companion star?
Or will the new claim that this rotation
speed is nothing more than an optical
illusion be vindicated?
Let me know your thoughts in the
comments below.
In 2022, astronomers using the Merchesen
wide field array discovered a strange
new radio signal that was arriving every
22 minutes. The astronomers were no
strangers to such repeating signals.
They typically come from pulsars,
neutron stars, which send intense pulses
of light across the universe as they
rotate on their axis.
But as they began to look deeper into
records of past observations, they
realized this signal had been arriving
at Earth since at least 1988 with
remarkable stability, far more stable
than is expected for a pulsar rotating
every 22 minutes.
If it was a neutron star, it was unlike
any they had seen before. So where was
this signal coming from?
I'm Alex Mccoan and you're watching
Astramm. Join me today as we grapple
with the mystery that lies behind this
signal which will challenge our
understanding of some of the most awe
inspiring objects in our cosmos.
The location of the source named
GPMJ1839-10
is roughly 18,000 lighty years away. Its
signal arrives as pulses that can last
any amount of time between 30 seconds
and 5 minutes. These pulses can appear
at any time in a window of just over 6
1/2 minutes, which is centered on 22
minutes after the previous pulse. To us,
this may seem like a great deal of
variation. 30 seconds and 5 minutes are
very different durations, and the pulse
arrival varying by over 6 minutes
doesn't paint a picture of a very stable
source.
But neutron star dynamics can be very
complicated and if the source is indeed
a neutron star then many factors can
affect the duration and arrival times of
the pulses that we receive.
Nevertheless, the astronomers were able
to spot this signal hiding in data from
the last 35 years and used this expanded
data set to average out the
fluctuations.
They calculated that the source was
rotating once every 21 minutes and 58
seconds as well as how much it had
slowed down. But to their surprise, they
calculated that this rotation period
remained unchanged over the past 35
years. Even though it is expected that
the source will slow down as it radiates
energy into space,
we can only say for sure that if the
source has slowed down, its rotation
period would not have increased by more
than 0.28
milliseconds over the 35- year period
because otherwise we would have been
able to detect this in our data. This is
an absolutely minuscule amount and it
shows that whatever the object is is
spinning with remarkable stability.
This usually isn't odd for a pulsar.
These are the timekeepers of the
universe, the clocks of the cosmos,
mechanistically ticking away with such
certainty that we can use them to
measure time across vast stretches of
the universe.
However, this level of stability is odd
for a pulsar that is rotating so slowly.
To understand what makes it odd, we need
to recap how pulsars work and what makes
them slow down over time.
Pulsars are neutron stars, the leftover
cause of dead super giant stars, which
barring black holes, are the densest
objects in the universe. Planets like
our own are made up of atoms which
consist of over 99.999%
empty space due to the vast separation
between the electrons and the incredibly
dense nucleus they are whizzing around.
But imagine an entire star made purely
out of the neutrons that are found in
the nucleus. No electrons, no protons,
no empty space. merely a teaspoon of it
would have as much mass as 11 times that
of the entire human population, all 8
billion people.
A typical neutron star is around 35%
more massive than our sun and squeezed
into a sphere that has the diameter
about as long as the island of
Manhattan. To call it dense would be an
understatement.
For reasons still unknown to
astrophysicists, the extreme environment
gives rise to an incredibly strong
magnetic field. What does this have to
do with the signals we receive from
pulsars? Where do the light waves come
from? To answer this question, we need
to understand a complicated process that
gives rise to the signal. An
exponentially growing shower of light
and matter, all spawning from a single
electron.
Near the magnetic poles of a neutron
star, an electron can be accelerated by
the magnetic field and emit a so-called
curvature photon tangential to the
magnetic field line. This marks, if you
like, the start of a pulse. The
curvature photon moves in a straight
line until the angle between its
momentum and the magnetic field line
becomes too great. Once this angle
reaches a threshold, the light
dissipates and imbuss its energy into
the quantum field of electrons. An
electron is created alongside its
antiparticle, the posetron.
The electron positron pair has some
momentum perpendicular to the magnetic
field lines which they spontaneously
dispose of in the form of synretron
photons.
These two synretron photons can each
then produce another electron posetron
pair after they reach the threshold
angle between their momentum and the
magnetic field lines.
This process repeats again and again,
exponentially increasing the amount of
photons and electronosetron pairs
created until the synrotron photons no
longer have enough energy to create
electron positron pairs, putting an end
to the cascade.
These photons then beam out into space
while the original electron continues
its journey generating more curvature
photons and more cascades as it moves
along the magnetic field lines. This
pair production cascade is why the light
of a pulsar is so intense that we can
detect a signal from this tiny stellar
remnant thousands of light years away.
But why do we see this light as pulses
rather than a continuously glowing
beacon of light shining at us? This is
because the magnetic poles of a neutron
star are rarely ever aligned with its
axis of rotation.
Just like on Earth, the magnetic north
pole that our compasses point to isn't
the actual geographic north pole the
Earth rotates around. So, the pulsars
are like great lighouses sweeping their
beams of light around the cosmos as they
spin. And for an observer far away, like
us on planet Earth, we see the beams
sweep past us again and again as the
pulsar completes its rotation on its
axis. These are the pulses of light that
our telescopes can detect. However, this
is light with very long wavelengths in
the radio part of the spectrum. Meaning
only a radio telescope can detect it.
The light that the cascade produced is
of the same wavelength with the peaks
and troughs of the light waves
fluctuating in unison. The light waves
are also polarized which means they are
all aligned along the same axis. This is
a hallmark of neutron stars and this is
precisely what we observe in the 22minut
signal. The signal also has fluctuations
that last between 0.2 to 4 seconds where
the axis of the light's polarization
suddenly changes by 90° perpendicular to
the original axis and then back again.
This effect is yet another signature of
the cascades at the poles of the
pulsars.
So much of our data points to a pulsar
being the signal that you'd think this
was an open andsh shut case. But one
variable that we've mentioned earlier
throws this entire theory into doubt.
The slow rotation rate of the neutron
star or rather the combination of the
slow rotation rate and the high
stability of the rotation rate of the
source.
You see, as pulsars lose energy by
shining their powerful beams into the
cosmos, conservation of energy will
ensure that the pulsar slows down.
Eventually, the pulsar will slow down so
much that it can no longer power the
pair production cascades and the light
emission starts to shut off. The pulsar
has entered the so-called death valley.
This graph plots neutron stars based on
their rotation period on the x-axis and
the rate of change of their rotation
period on the yaxis.
Death Valley is shown in this gray band
running through the middle. And any
pulsar that has properties below this
line should not be shining as the bright
lighouses they usually are.
We see that our signal is below even the
lowest line marking the death valley.
meaning that if it were a pulsar, it
should be well and truly switched off.
And yet, we are detecting it. Look at
the cluster of other known neutron stars
on this graph. They usually spin between
10 times a second to once every second.
In comparison, our signal has a spin
rate of once every 1,318
seconds, over a thousand times slower
than the typical pulsar.
This would be fine if it was also
slowing down quickly, which equates to
moving this data point upwards on this
graph above the Death Valley. Such rapid
energy loss would power the pair
production cascade necessary to light
the beacon of the neutron star. Yet, the
neutron star is mindbogglingly stable,
and it makes no sense that we can detect
it. The astronomers who found the signal
considered an alternative mechanism that
might explain how a neutron star with
such properties might have produced this
light. Maybe the neutron star is a
magnetar, a neutron star that has an
unusually strong magnetic field, greater
than 10,000 times the strength of the
weakest neutron star magnetic fields.
Magnetars are known to undergo star
quakes, cataclysmic events that release
the tension in the upper crust of a
neutron star. These stresses are
produced by the strong magnetic fields
of the magnetar as well as the slowing
down of the magnetar rotation. A fast
spinning magnetar will bulge in the
middle due to the centrifugal force
distorting the star from a perfect
sphere. As the magnetar slows down, the
outer layers need to readjust to a new
equilibrium and lose some of the bulge
they have. The crust snaps into a new
position, causing magnetic fields to
temporarily realign and powering the
release of the energy as light that we
can detect on Earth.
The most powerful star quake detected,
that of SG1806-20
in 2004, released so much energy that if
it had taken place as far away as 10
light years from Earth, it would have
caused a mass extinction event. If
something is able to light the beacon of
a dead pulsar, it would be this. So,
could GPMJ1839-10
be a magnetar that has undergone a star
quake? Have we resolved the mystery of
the 22-minute signal? It seems not. We
expect these star quakes to also emit
light in the X-ray part of the spectrum.
Yet, no X-rays can be detected from the
position of the source roughly 18,000
lighty years away.
It also wouldn't make sense for a
magnetar outburst to be going on for
three decades. The star quake is a
temporary phenomenon and the energy
dissipates within a few years at most.
It is simply incomprehensible that this
signal would have existed for 35 years
if it was indeed a magnetar.
Once again, the unique properties of our
signal exclude it from being a neutron
star, even an unusually powerful one
that has undergone a special event, such
as a star quake. But what else could the
source of this mysterious signal
possibly be? The astronomers who
discovered the signal proposed a few
alternatives for the identity of the
source. One possibility is a highly
magnetic white dwarf. A white dwarf is
another type of remnant left from the
recent death of a star, but one that
didn't have enough mass to collapse the
empty space in the atoms to become a
neutron star. A remnant that has an
unusually strong magnetic field could
produce radio emissions. And as it is
not a neutron star, it could get away
with being as slow and stably rotating
as the source of our object while doing
so.
The issue is this would require an
exceptionally strong magnetic field
greater than any we have spotted on a
white dwarf. A sco is the only known
radio pulsar that is actually a white
dwarf and its radio missions are a
thousand times less luminous than the
source of our 22-minute signal.
So if a white dwarf is unlikely, what
are our other options?
Astronomers have observed low frequency
radio waves coming from the interactions
between stars and exoplanets as well as
a binary of two brown dwarfs rotating
around each other. But this emission is
typically weaker, around 100 million
times weaker than the source of our
signal. In the end, it seems like none
of our theories can explain the 22minut
signal. While the unresolved question
about the source of the signal may feel
frustrating, this is precisely the kind
of mystery that astrophysicists look
for. When scientists find new data that
challenges our long-held theories, they
can usher in revolutions in our
understanding of the universe around us.
Here, our already shaky understanding of
neutron stars is being challenged. The
astronomers are confident that the ease
with which they identified this signal
means similar sources lie out there in
the galactic plane waiting to be
identified. Just like GPMJ1839-10,
the other signals might already be
lurking in the data we have collected.
Identifying more of these signals will
shed light on the process powering
emission beyond the neutron star Death
Valley.
Whatever lies behind the 22-minute
signal, we are sure to learn of an
entirely new phenomenon that we have
never seen before. Isn't that exciting?
What do you think could be the source of
the 22-minute signal? Let me know in the
comments below.
800 light years away, there's an unseen
antimatter factory churning out high
energy posetrons.
Tiny particles of antimatter that are
streaming through the cosmos and
colliding with our planet.
For much of history, we didn't know this
strange source existed. Most of the
positrons bombarding us went completely
undetected, instead getting absorbed in
our planet's atmosphere. It wasn't until
we started looking from beyond the
bounds of our planet that we noticed
them. In 2011, NASA's Alpha Magnetic
Spectrometer, a state-of-the-art
particle detector some 200 m up aboard
the International Space Station, was
switched on. What did it find? You
guessed it, posetrons.
The presence of these subatomic
particles was to be expected, but not in
the numbers they were finding.
Such was the sheer volume of posetrons
being detected that the usual sources
like natural radioactive decay and
cosmic rays no longer offered a
sufficient explanation.
So where were they coming from?
We've only recently been able to trace
the culprit of this cosmic antimatter
shower. And it all comes down to another
high energy discovery. a strange
gammaray haze named gaminga first
identified in the 1970s.
What is this mysterious source of gamma
radiation and what does it have to do
with the unusual abundance of high
energergy posetrons hitting our planet?
I'm Alex Mccoan and you're watching
Astramm. Join me today as we tune into
the enigmatic frequency of Gaminga whose
gamma radiation has lit up the world of
astrophysics for decades.
Up in our night sky, nestled in the
Gemini constellation in the northern
celestial hemisphere, there is something
peculiar going on. In 1972, NASA's small
astronomy satellite 2 or SAS2 identified
an unknown source of gamma radiation.
But with the technology available at the
time, the best it could do was trace its
origin to this wider region of our Milky
Way. So, the radiation's ultimate source
remained hidden among the stars for
decades. Nevertheless, it was given a
name, Gaminga, as coined in 1976 by
Italian physicist Giovanni Binyami, who
would dedicate his career to studying
it. It's a play on words, a combination
of Gemini, the region where it's
located, and gamma, the type of
radiation it emits. Gaminga is also a
pun in Bingyami's Nelan dialect, meaning
it's not there. A fitting name for a
gamma ray haze with unknown origin.
It wasn't until 1983 when Binyami and
his team finally had their big break.
They managed to identify a weak X-ray
signal from Gaminga using the Einstein
X-ray satellite. This meant although its
exact position remained unknown, they
could narrow down their search area and
were getting closer to uncovering
Gaminga's hiding place. But it didn't
answer the big question, what is it? As
astronomers could still only offer vague
guesses about the true nature of the
source.
That was until 1991 when they had
another lucky break. Two separate
missions identified radiation coming
from Gaminga, and they weren't constant
signals, but pulses. The first of these
discoveries was made with a Germanbuilt
X-ray telescope known as Rosat, short
for Rken Satellite, named after the
German word for X-rays.
Rosat was the first to identify pulses
in the X-ray signal coming from Gaminga
and soon after they were also confirmed
in the gamma wavelengths by the
energetic gammaray experiment telescope
or egret a telescope aboard NASA's
Compton Gammaray Observatory satellite
not only did these complimentary
observations demonstrate that the X-rays
and the gamma rays were both coming from
Gaminga but for the first time they
revealed what Gaminga was with a period
of 0.237
seconds flashing as it spins around its
axis a little more than four hertz or
four times per second. Gaminga behaved
like a pulsar.
A pulsar is a type of neutron star that
spins rapidly, emitting beams of
radiation that sweep across space like a
cosmic lighthouse. From across the
galaxy, most pulsars appear to flash in
radio waves anywhere from a few times a
minute to as fast as 700 times per
second. And at this point in the early
'90s, they were incredibly rare. You
see, before Rosat and Egret, only two
other high energy gammaray pulsars had
ever been identified. The crab and Vela
pulsars. And Crab and Vela were
different to Kaminga in a couple of key
ways. First, in addition to gamma rays,
both of these pulsars also produced
radio waves and were therefore visible
using radio telescopes. So if Kaminga
was a pulsar, then it would be the first
discovery of one that was apparently
radio silent only emitting enough
radiation to be seen in the gamma and
X-ray wavelengths.
And second, Crab and Veil were
surrounded by their respective nebula,
remnants from when they were created
from supernova explosions.
But Ginga's nebula was conspicuous by
its absence.
So why is Gaminga, this powerful source
of gamma rays, so good at hiding from
our radio telescopes? Where is its
nebula? Or could it be a different type
of object altogether?
Well, the answer to the first question
is in part because we hadn't been
listening properly due to the
limitations of the available technology
and due to our understanding of the
radio emissions of such stellar
remnants. You see, while radio pulsars
can emit radio waves across a wide
bandwidth from as low as 17 MHz to above
87 GHz, around half the radio spectrum.
Not all of these frequencies travel well
through space. Even though we've known
since the 1970s that radio pulsars often
peak between 100 to 200 MHz, where they
are intrinsically brightest, things like
the interstellar medium, background sky
temperature, and effects from the
ionosphere mean that lower frequencies
are dampened as they make their way
across space, resulting in very weak
signals that are much more difficult to
detect.
Because those radio signals are so weak,
most radio telescopes hadn't been
looking for them. Instead, confining
themselves to searching for signals
between 430 and 1,600 MGHertz.
This would have been fine had gaming
behaved as expected for one of its kind.
Since it did not, it took until 1997 for
scientists to realize what was
happening. Three independent
observations from the Pusheena Radio
Astronomy Observatory were able to
identify extremely weak pulses from
Gaminga using a sensitive transit
antenna. The faint radio pulses came in
around 100 MHz, which explains why
previous radio searches for Gaminga had
come up silent. Turns out Gaminga wasn't
truly hiding and had been sending us
signals. We just weren't listening
correctly.
That same year, a team led by the late
astronomer Yanuj Gil theorized that
another reason Gaminga had appeared to
be radio silent may be its magnetic
field. Models showed that radio waves
may be absorbed or refracted within the
pulsar's magnetosphere, leaving only
weak pulses around 100 megahertz to be
detectable. This would effectively leave
it quiet at the higher radio bands than
most telescopes used.
Confirming Gaminga was a pulsar and
specifically a gammaray pulsar was a big
deal. In fact, 99% of its output is in
the gamma range, making it one of the
brightest gamma ray sources in our
entire galaxy.
It is, as it turns out, all that's left
after a star several times more massive
than our sun exploded about 350,000
years ago.
But its relative radio silence and its
apparent lack of a nebula weren't the
only unusual things about this pulsar.
When Italian astrophysicists, including
Bingami, Gaminga's name giver, compared
a series of observations from the
European Southern Observatory's 3.6 m
telescope and new technology telescope
with observations from the Canada France
Hawaii telescope. They found that
Gaminga was moving. Not only that, it
was traveling at an unusually high speed
of around 0.2 arcsec per year. As a
reminder, an arcsec is a very small unit
of angular measurement used when we need
more precise measurements than a degree
would allow. Within each arc degree,
there are 60 ark minutes and within each
ark minute are 60 ark seconds. These arc
seconds are a common unit used in
astronomy to talk about the movement of
objects across the sky from our
perspective on Earth. If you were to
draw a circle around the orbit of the
moon around the Earth, there would be
360°
around that circular path. So, at any
given time of day or night, assuming
nothing is blocking your view of the
horizon, you can see about 180° of the
sky. And from the horizon to the zenith,
the top of the sky is 90°.
If you hold out your little finger at
arms length and close one eye, the tip
of your little finger covers about one
degree of the sky roughly. Next time
you're outside on a clear night, try
this and see if your little finger can
cover the moon. It should because the
moon takes up only about half of a
degree or about 31 ar minutes in the
night sky.
Gaminga traveling 0.2 Two arc seconds
across our sky each year may not sound
like a lot, but from our perspective on
Earth, the typical star only moves a few
thousandth of an arcsec per year. Yet,
despite being 800 lighty years from us,
Gaminga will travel 30 ark minutes, the
equivalent to the apparent diameter of
the moon across our sky in just over
10,000 years. In other words, this
stellar corpse is racing through the
galaxy at nearly 210 km per second.
Heading towards the border between the
constellations Gemini and Lynx. And at
its current rate of motion, Gaminga will
remain in Gemini for another half
million years. But it may need a new
name after that. However, this
mysterious pulsar gets stranger still.
It is its vast speed that helps produce
another feature that scientists were
about to discover. As it hurles through
space, Gaminga leaves behind two ghostly
X-ray tails that streak 3 trillion km
across the sky. As I discussed earlier,
despite the fact that this fastmoving
pulsar is nearly radio silent, it
certainly isn't quiet in the gammaray
and x-ray wavelengths.
In 1999, ISA's X-ray multi mirror
mission or XMM Newton was launched to
peer deeper into this X-ray universe.
And four years later, a team led by
Patrica Caraveo uncovered these
cometlike X-ray trails.
Their shape and brightness are partly
explained by the shock wave created by
Gaminga's motion through space and its
rotation as a pulsar. But they are also
revealing of another attribute. Gaming's
colossal mass.
Measuring only about 20 to 30 km across.
Gaminga is extremely dense containing
about as much mass as 1 and a half of
our suns. To put that in perspective, if
you had a teaspoon of neutron star
material, it would weigh about 4 billion
tons, as much as 10,000 Empire State
buildings.
As this dense, high mass object races
forward through the low density
interstellar medium, just 0.06 to 0.15
atoms per cm. It compresses the
interstellar medium and its own embedded
magnetic field by a factor of four.
Meanwhile, the incessant spinning of the
neutron star creates an environment
where electrons and their anti-atter
counterparts called posetrons can be
accelerated to extreme energies powerful
enough to emit high energy gamma rays.
While most of these electrons are seen
in the gamma radiation that escapes from
the pulsar, some get trapped and spiral
within this enhanced magnetic field. In
these images from a computer model, the
tails can be seen streaking along the
edges of Gaminga's three-dimensional
shock wave. Like the wake created by a
boat going through water. Only this boat
is more massive than our sun. And the
wake is made up of extremely high energy
X-rays.
But the final piece of the Gaming puzzle
wasn't discovered until 2005.
Its nebula.
Taking the form of a shell of neutral
hydrogen gas with a radius of 0.4 parex
wide. It turned out to be what we call a
pulsar wind nebula.
This type of nebula is created from the
wind plasma that emanates from a
pulsar's magnetic poles. The plasma made
of charged particles that can be
accelerated to near light speed
surrounds the pulsar, creating a nebula
of high energy particles that give off
strong X-ray emissions. With the
confirmation that Gaminga did have a
nebula, its identity as a pulsar could
finally be confirmed. But Shandra went
even further.
In addition to imaging Kaminga, Shandra
also looked at a second pulsar called
B0355
+ 54. And by comparing the two,
astronomers uncovered another possible
explanation for the absence of radio
pulses from Gaminga. On the surface,
these pulsars seem quite similar. They
are both about half a million years old,
and they spin about four to five times
per second. However, as you know,
Gaminga is seen primarily in gammaray
pulses with no bright radio emissions.
By contrast, the other pulsar, which
I'll refer to as pulsar B, is not seen
in gamma rays and instead is one of the
brightest known radio pulsars.
How could these two pulsars be so
similar yet so vastly different in how
we see them?
The answer may be as simple as how each
of these pulsars are oriented relative
to our observation from Earth.
Astronomers believe that these images of
Gaminga and Pulsar B have revealed their
spin axes and uncovered a reason for why
radio and gammaray pulses may be present
or absent on different pulsars.
Like our own magnetic field around
Earth, both of these pulsars have
magnetic poles close to their spin
poles. These poles are where the beams
of pulsing radio emissions come from.
You could try to model this if you
skewer a little foam ball right down the
middle. The foam ball is a pulsar, and
the radio beams coming from the poles
are represented by the wooden skewer
coming out both ends. If you spin the
ball around the skewer like a spin axis,
you create an equator around the middle.
To illustrate the gammaray source along
the spin equator called the Taurus, you
could cut a hole in a paper plate and
squeeze it over the foam ball. Now
you've got yourself a disc of gamma rays
beaming out from the equator in every
direction. With gaming, the edge of the
paper plate is pointing towards us,
meaning the gamma rays are heading to
Earth. But for pulsar B, its relative
position to us is at a different angle
as if looking at the flat surface of the
plate. The gamma rays are moving
perpendicular to our line of sight,
therefore missing Earth.
Let's look again at the two Chandra
images of Ginga on the left and Pulsar B
on the right along with artist
illustrations of what astronomers
believe the Pulsar wind nebulas look
like for each of these. In the image of
Pulsar B, the long trailing blue tails
represent the radio jets emanating from
his poles and the skewers coming out of
both ends. Only instead of being
straight like a wooden skewer, Pulsar B
is moving so fast through space that
these jets appear bent backwards,
trailing behind as the pulsar moves
through space. Now look at the image of
Gaminga. Here the long twin tails on
either side of the image are the radio
jets trailing behind as it too rushes
through space. But this time instead of
pointing almost directly toward and away
from our vantage point on Earth, these
jets appear to be coming off to the
sides, not aimed at Earth. So when
astronomers look at Gaminga, they see
powerful gammaray emissions from the
spin equator, but the radio jets point
to the sides and remain unseen. And when
they look at pulsar B, the opposite
happens. The radio jets are pointed
almost straight toward our planet while
the gammaray source at the equator is
missing Earth. Sometimes the most simple
explanation is the correct one. And that
finally brings us back to the decadesl
long mystery of an unusual abundance of
antimatter bombarding our planet.
For more than a decade, a particle
detector called the Alpha Magnetic
Spectrometer or AMS2 has been attached
to the International Space Station,
collecting information on antimatter,
dark matter, and cosmic ray sources. As
a reminder, cosmic rays are energetic
particles, fragments of atoms that
travel through space at nearly the speed
of light. These can be made by the sun,
by supernova explosions, or other cosmic
means. And in 2013, the first results of
the AMS2 experiment were announced. The
detector had recorded more than 400,000
posetrons, the largest sample of cosmic
ray posetron data ever collected. and
increasing the world's total cosmic ray
posetron data by 100fold.
For years, many astronomers and
physicists hoped that this excess
antimatter may be the byproduct of a
dark matter annihilation, offering
possible clues about this mysterious
substance. After all, dark matter could
make up around 27% of the cosmos. And
yet, we still don't know what it is.
Like regular matter, dark matter holds
mass and takes up space. But it doesn't
seem to absorb, reflect, or interact
with light, at least not in a way we can
detect. Some theorize that dark matter
may be made of yet unidentified types of
particles. Whatever it is, scientists
had high hopes that the overabundance of
antimatter being detected aboard the ISS
may hold clues about dark matter's true
nature. Unfortunately, they've been left
disappointed. The more scientists dig
into the data, the clearer it's
becoming. The most likely source of
these posetrons may actually be pulsars.
Astrophysicists had long suspected this,
but until 2017, there simply wasn't
proof. It was the high alitude water
chancery
that finally added evidence to this
hypothesis. A small halo of gamma
radiation was identified surrounding
Gaminga with trillions of times more
energy than is visible to our eyes from
five to 40 trillion electron volts. The
sort of radiation usually produced by
posetrons. This was the first real
observational evidence pointing to a
pulsar as a potential source.
Pulsars naturally surround themselves
with a haze of both electrons and their
posetron counterparts as a result of the
stars intense magnetic field. This
intense magnetic field pulls particles
from the pulsar surface and accelerates
them to near the speed of light.
Scientists think that these accelerated
posetrons and electrons are then
colliding with starlight boosting the
light to higher energies which then
radiates as the gammaray halo observed.
But based on the size of the halo the
hawk team saw, gaming's posetrons would
rarely have the energy required to reach
our planet. And so they believed the
excess posetrons must have a more exotic
source. That was until stunning new
information was uncovered a few years
later thanks to a team led by
astrophysicist Matea Dearo.
Using a decade of gammaray data from
Gaminga acquired from Ferm's large area
telescope which is able to observe lower
energy light than the Hawk gammaray
Observatory. The Maro's team was able to
subtract out all other gammaray sources
to reveal a spectacular glow coming from
Gaminga much much bigger than what the
scientists had ever seen before.
The vast oblong halo of glowing gamma
rays at an energy of 10 billion electron
volts spanned 20° of the sky, similar to
the area the big dipper constellation
occupies. And that's not all. The glow
of gamma radiation is even bigger at
lower energies. If we could see it all
with the naked eye, Gaminga's gammaray
glow would dominate our sky, covering an
area 40 times bigger than the full moon.
With this new information,
astrophysicists found that the size of
Gaming's halo meant that this one pulsar
alone could be responsible for as much
as 20% of the excess posetrons detected
near Earth. From there, it's no stretch
to imagine that other pulsars are the
most likely culprit for the remaining
antimatter abundance we found. This
explanation may not have solved the
mystery of dark matter, but it is
certainly a magnificent revelation.
It was Jocelyn Bell who discovered the
first pulsar in 1967, back when people
thought that those regular signals could
be the work of extraterrestrial life. In
the nearly 60 years that have passed
since, we have found thousands of
pulsars, and our understanding of these
neutron stars has grown with everyone.
And since Gaminga was identified as only
the third known gammaray pulsar in 1991,
we've now spotted over 300 thanks to
NASA's Fermy mission. But given
Gaminga's track record of defying
expectations and furthering science, I
like to think that this particular
pulsar has more secrets still to reveal.
We've all seen pictures of galaxies,
often glorious objects with spectacular
colors and shapes. However, because they
are static images, it may make you
wonder how they rotate.
The first obvious thought is that they
spin around an axis perhaps looking
something like this as they do so.
Would it surprise you to hear that this
is totally wrong?
For a start, galaxies are not solid
objects, but rather made up of millions
to trillions of stars. Each star follows
their own orbit, although they are often
going in the same direction at least.
But actually, one of the main reasons a
spiral galaxy does not orbit like the
first example is that angular momentum
would wind the arms up into tighter and
tighter spirals.
We don't see this. So, something else is
at play.
The leading theory is that these arms
are caused by density waves, meaning a
galaxy's rotation would in fact look
like this. Here the arms stay in place
or at least move extremely slowly as
stars and gas pass through them.
Another theory is that shock waves
produced by supernova and stellar winds
are the cause of the arms. These
theories might not be mutually exclusive
and both processes may be at work here.
Density waves are potentially caused by
the self-gravity of stars as they orbit
after they have been perturbed by
another force.
As stars have a gravitational influence
on each other, eventually a pattern
forms where their orbits meet around
certain areas in the galaxy.
Very, very interestingly, density waves
are even seen in certain parts of
Saturn's rings. Here you have a section
of ring that appears like the inside of
a tree trunk. But this is not the case.
In this region, the ring is influenced
by the gravity of small shepherd moons
tucked inside the rings. What you are
actually looking at is one very tightly
wound ring, a bit like an LP record. And
just like with a galaxy, this arm stays
the same shape, never getting tighter or
looser.
Within these arms is where the majority
of star formation takes place in a
spiral galaxy. The gas and dust within a
galaxy clump up in these arms too, which
is why you often see star forming nebula
dotting the arms. The arms are also
brighter, not just because there are
more stars here, but also because all
the hot, young, bright stars are found
in these regions.
Because the hottest types of stars are
so short-lived, by the time they move
away from the arms, a lot of them will
have already burned out.
Another interesting phenomenon to do
with spiral galaxies is something caused
by dark matter. In the early universe,
when dark matter was more disperse,
stars within galaxies that are dominated
by normal matter would orbit a lot
slower around the outside of the galaxy
than towards the center.
However, today stars are moving a lot
faster near the edge of the galaxy
thanks to the influence of dark matter.
Dark matter is mysterious in that it
cannot be seen or observed in any way
other than by its gravitational
influence. Dark matter seems to have
clumped towards the center of galaxies
over time, making stars orbit faster
than they should around the edge of a
galaxy if only gravity from normal
matter was accounted for. Other theories
also exist about why this may take
place, but these would have to change
the way we currently understand physics.
Anyway, how do we know about this change
in the way stars orbit galaxies? Well,
of course, we can see back in time when
we look at extremely distant objects.
Stars within galaxies billions of light
years away seem to orbit slower than
stars much closer to us. And this effect
scales depending on the distance to the
galaxy.
Of course, though, there are some rule
breakers out there. While most galaxies
have stars that orbit like this, a few
have been spotted that have leading
outer arms. One example is NGC 4622,
a bizarre galaxy that rotates in the
direction the arms are pointing. This
was hard to accept at first until
smaller inner arms were also found.
This unusual galaxy has probably
experienced a merger in its not
tooistant past, which likely caused this
phenomenon.
Another rule breaker is the black eye
galaxy, which has two counterrotating
discs of gas and dust. The inner disc,
where you can see all the dust lanes,
rotates normally, whereas gas in this
outer disc rotates the opposite
direction. Interestingly, stars in this
outer region do not seem to be orbiting
retrograde, meaning it is just the gas
that does so. It is believed that gas
must be still getting fed into the
galaxy from the intergalactic medium or
that this galaxy also emerged with
another extremely gas-rich galaxy.
The last thing I wanted to show you
today is the other major category of
galaxy, elliptical galaxies. Elliptical
galaxies contain stars that are
generally much older than those found in
spiral galaxies because the dust lanes
in these galaxies have been exhausted,
meaning stellar production has all but
stopped.
In these kind of galaxies, stars are
very much independent from each other,
following their own rather elliptical
orbits. Sometimes galaxies can exhibit
characteristics of both types of
galaxies. These are known as lenticular
galaxies.
These galaxies have dust rings which
haven't fully been exhausted yet and
they have quite a ghostly appearance.
Star formation does appear to be a
factor in keeping spiral arms defined as
once the stellar building blocks dry up,
we've seen examples of spiral galaxies
losing their definition. Perhaps
lenticular galaxies are the midway point
between spiral galaxies and elliptical
galaxies.
So, there we have it. A look at how
galaxies rotate.
When you think about the North Pole, you
don't expect it to go anywhere. And you
certainly don't expect it to change
places with the South Pole. That would
just be wrong. Our magnetic compasses
would all point the wrong way. We'd need
to update our maps. Birds would probably
be horribly confused. And yet, although
they sound like something out of science
fiction, geomagnetic reversals like this
are real, they've happened before, and
the process behind it might be a lot
more dangerous than you'd think. To be
clear, it's not the reversals themselves
that are potentially dangerous. It's the
buildup. During those times, the Earth's
magnetic field, the shield around our
planet that keeps us safe from deadly
solar radiation, will drop to as low as
10% of its current strength, leading one
group of scientists in 2021 to predict
climate shifts and mass extinctions. And
others to describe satellites being
destroyed, electrical grids going
offline, and deadly radiation raining
down on us for hundreds or even
thousands of years.
This is troubling when you consider that
we are a couple of hundred,000 years
overdue for our next geomagnetic
reversal. And based on fluctuations in
the Earth's magnetic field that
scientists are detecting right now, the
buildup to a geomagnetic reversal may
even have begun already,
which begs the question, should we be
worried?
I'm Alex Mcolen and you're watching
Astramm. Join with me today as we
explore the science behind geomagnetic
reversals and find out whether the next
one will be an apocalyptic scenario or
whether it'll lead to nothing more than
a few lost birds. What truly happens
when things go south?
Let's start by trying to understand
where the Earth's magnetic field comes
from in the first place.
It's not a given that our planet would
have a magnetic field. The two planets
flanking us, Mars and Venus, do not have
one. And yet, the Earth does, which is a
good thing, as without one, there is a
very real chance life would not have
been able to arise here in the first
place.
Thanks to the protective cocoon of this
field, deadly solar radiation is
deflected away from the planet's
surface, allowing things to flourish
without all that radiation breaking down
our DNA, causing mutations and cancers.
Scientists are still trying to figure
out all the particulars of why certain
planets have fields and certain others
don't. But the current leading theory is
that the Earth's core acts as a giant
dynamo.
It's a principle of physics that you can
use electrical fields to create magnetic
ones and vice versa. This is the
principle that power plants work under.
Moving a magnet through a coil of wires
causes electrical current to start to
flow as that changing magnetic field
exerts a force on the electrons present
there. But similarly, the motion of
electrons creates a magnetic field to
form in perpendicular circles around the
direction of motion in accordance with
Faraday's law of induction.
But the way this applies to the earth's
core is a delicate complicated process.
To start with, our core needs to be at
least partially liquid, which
fortunately is true.
Above the solid inner core that lies at
the heart of our planet is a liquid
outer core, where the pressure isn't
quite high enough to keep things in a
solid state. It's very hot in the outer
core, though, 6,000° C at its warmest
point. So hot that it rivals the surface
temperature of the sun, which when
combined with the lower pressure
compared to the inner core, is more than
enough to keep the iron and nickel that
makes it up flowing down there.
The temperature drops as you move away
from the center of the Earth. This gets
circulation going. Hot conductive
material from the warmer deeper regions
of the outer core rises, then cools,
then falls again, creating loops and
currents of flowing material. Our
electrical field starts to be generated.
But if there are many of these flowing
loops, which in theory there would be,
why does Earth only have one north pole
and one south pole? Surely the created
magnetic fields would be all over the
place.
Well, there is thought to be an extra
force at play that takes all these
fields and unifies them, pointing them
in the same direction. This force is
thought to be the corololis effect.
Dynamo theory states that the corololis
effect causes these flows of iron to not
rise and fall as straight lines, but as
spirals.
The spinning of the earth causes them to
gently be spun in turn, creating giant
springs.
As each segment of each spring is
creating a magnetic field in a circle
around it, the net result is that the
inside of these springs creates a solid
unified field that all moves in the same
direction upwards, while the outside
brings that magnetic field looping back
down again and back in to the bottom of
the coil. In short, it creates the
well-known magnetic dipole north and
south that we see today.
However, if there's anything that you
should take away from this, it's that
this process is precarious as it is
based on a lot of liquid iron
essentially just slloshing around which
is not very consistent. Our magnetic
field thus has little fluctuations and
wobbles all the time. We see this in
different ways, but a big one is that
our north pole is constantly moving.
Since scientists began keeping track of
it in 1831, the North Pole has gradually
shifted about 1,100
km, leaving its original location in
Canada and moving up towards Siberia.
Its rate of motion is also increasing,
going from 16 km a year to roughly 55 km
a year. A big jump.
This might still be akin to just the
momentary wobbles of a spinning top,
though. Yes, it deviates somewhat, but
it always remains roughly upright.
That's a far cry from a complete
reversal.
However, scientists are certain that
such reversals have happened before.
They even have a specific number,
183 times in the last 83 million years.
How do they know? The answer lies locked
in our Earth's surface iron.
When magma erupts from the Earth's
mantle, it can contain small amounts of
iron. As these can move freely in the
molten magma, they tend to orient
themselves in the direction of the
Earth's magnetic field. However,
scientists noticed that there were
layers of geological history where the
iron was pointing one way and layers
where it was pointing in the reverse
direction. Their explanation, the entire
pole of the planet had flipped. On
average, these flips seem to happen
every 450,000
years, although the last few have only
got 300,000year gaps between them.
Comparatively, it's been 750,000
years since the last reversal. You might
think that we're overdue for one, and
some have made that claim. However,
scientists have found that there's
little rhyme or reason to the timing of
these flips. One of the longest gaps
between flips took place in the
Cretaceous period and it lasted 40
million years. The record holder, the
Kiean reverse supercron, was 312 to 262
million years ago, 50 million years with
no reversal.
Scientists are still trying to
understand what causes these flips.
However, the current theory is that
something, perhaps some interplay
between the mantle and the outer core
causes a fluctuation in the core
spinning. This disrupts the spiraling
shapes of the core's flow, breaking them
down. The magnetic field of the Earth
stops being unified and generally
becomes a sprawling mess, fighting
against itself. Several poles might
temporarily arise during this period of
shifting magnetic confusion. While in
time things settle down and the spirals
reassert themselves, it seems random as
to which way they will do this. Meaning
about half the time our magnetic north
pole reappears over the geographical
south. This reasserting can take 1,000
to 10,000 years.
All right, but would that really be the
end of the world? Why does this matter?
Well, during that period before the
poles reassert themselves, our Earth's
magnetic field drops to as low as 10% of
its current strength. In theory, this
could leave us much more vulnerable to
all the solar radiation space throws at
us. We could see auroras reaching much
further south during that time. Skin
cancer rates would increase. Our
satellites would find themselves with
not enough shielding. Radiation would
fry their circuits, causing them to
malfunction, shut down, and potentially
even slowly fall from orbit.
Our electrical grid would be much more
vulnerable to solar storms, which could
lead to large segments of the Earth's
population without power. With no
electricity or satellite communication,
it would be a devastating blow to our
global civilization.
It could be worse than that. A research
team from the University of New South
Wales in Sydney even linked one of the
most recent weakenings of the magnetic
field, the Lashamps event, a temporary
800year wobble rather than a full flip
to megapornal mass extinctions in
Australia, including the deaths of
Droaton,
giant Australian wombats, and Procopadon
Gallayia, giant kangaroos.
Temporary wobbles like this are known as
geomagnetic excursions rather than full
reversals and they happen over much
shorter time frames. Their transition
periods can last as little as 200 years
rather than 10,000 which can be much
more difficult for species to adapt to.
In their 2021 study, they argued that
there was a spike in atmospheric
radiocarbon levels caused by the
collapse of the Earth's magnetic field,
indicating climate shifts that could
have led to these extinctions. The
timing lines up uncomfortably.
But how real are these risks? Honestly,
it's a mixed bag. A point in our favor
is that other than this recent study,
there is no indication that magnetic
field reversals have ever coincided with
mass extinction events. It seems like
many reversals have come and gone
without affecting animal or plant life
at all. And even in this study, such
mass extinctions seem to have been
limited in scope. There is no claim from
the researchers that this was a global
phenomenon. Other parts of the world
remained unaffected even during the
Lashamps event.
It seems that a perfect storm might have
been in play where specific conditions
over Australia left it more vulnerable
to solar radiation.
In terms of our global society, it's
worth noting that these magnetic changes
would take many lifetimes to complete,
even at their fastest. This would be
slow enough that we could come to terms
with our new reality. If our satellites
don't have enough shielding, we would
have time to build some that were better
protected. If solar radiation becomes a
larger risk, we could remain indoors
more, sun cream might become more
powerful to mitigate the dangers of
cancers if not remove them entirely.
And according to NASA, even if our field
were to significantly weaken, it's not
like we would be left without
protection. Our atmosphere itself can
catch radiation, meaning that we would
remain safe from solar winds and cosmic
radiation, at least to some degree. It
would take far longer than 10,000 years
for our atmosphere's ozone to be
stripped away. But I would be surprised
if there wasn't at least some turmoil,
at least while we adjusted to living
under a reduced magnetic field. Big
changes to how a society operates are
always painful. And this isn't entirely
hypothetical. Did you know the Earth's
magnetic field has been steadily
weakening for the last 200 years? It
would take another 1,300 years for it to
vanish completely. So, there's plenty of
time for it to stop its current downward
trend. And there's no reason to think
this isn't just a temporary wobble. But
on top of that, there is also the South
Atlantic anomaly to consider. A section
of the Earth's magnetic field that is
already showing signs of significant
weakening that covers most of the space
around South America and the neighboring
ocean.
This zone might not influence life on
the ground, but is dangerous enough that
it has fried satellites and threatened
astronauts. A Hubble telescope has to
turn itself off every time it flies
through it. Imagine that. But across the
entire globe, that's what we might
expect while the poles are reversing.
Concerningly, the South Atlantic anomaly
has been growing continuously since we
started keeping track of it, possibly
suggesting the approach of either
another geomagnetic wobble like the
Dashamps event or that a full-blown
reversal is already upon us. If it
happens, it won't likely be something
that ends civilization as we know it.
But if the study about Australian
megapora is correct, it isn't going to
be without impact either. species could
die. Humans will have to accommodate a
very different, more hazardous space
environment.
It's interesting to learn about
geomagnetic reversals and their
potential impacts on the planet. But
while we are not likely to see one
happen in our lifetimes, for the
generations of humanity after us, this
might turn out to be a lot less
hypothetical. They might be seeing it
firsthand.
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