Our planet is haunted.
Now, you might think that is an odd
thing to claim for an astronomy channel,
but there have been whispers among
astronomers that something is out there.
Ghostly specters lurking in our orbital
path.
Entities
that have eluded scientific detection
for decades,
drifting in perfect balance between
cosmic forces.
Some claim to have captured faint images
of these ethereal silhouettes looming up
to nine times wider than Earth itself.
Yet others have searched the same
regions of space and found nothing at
all.
For over six decades, astronomers have
debated their existence. Are these
mysterious entities merely elaborate
optical illusions? Or something truly
extraordinary hiding in plain sight?
What celestial phenomenon could
simultaneously be so large yet remain so
elusive? Is the moon truly Earth's only
companion in our journey around the sun?
I'm Alex Mccoan and you're watching
Astramm. Today, we're investigating one
of astronomy's most enduring mysteries,
the controversial ghost moons that may
be silently accompanying our planet
through the cosmos.
This ghost story begins in 1961 when
Polish astronomer Kazmir Cordfki first
spotted two diffuse patches of sky that
kind of looked like clouds through a
telescope which were located
suspiciously near the stable L4 and L5
Lrangee points of our Earth moon system.
In case you aren't familiar with Lrangee
points, let me quickly explain.
Lrangee points are positions in space
where the gravitational forces of two
large bodies are balanced by the
centropedal force required for a smaller
object to move with them. This creates a
sort of gravitational equilibrium that
allows the smaller objects to maintain a
position relative to the two larger
bodies. Lrangee points were named after
the Italian French astronomer and
mathematician Ysef Louie Lrange after he
published a prize-winning paper about
this phenomenon in 1772.
While we're going to be talking about
the Lrangee points present in our Earth
Moon system in this video, similar
points exist for other two body systems
such as between the Earth and the Sun or
Jupiter and the Sun. In any two body
system, there are five spots where
gravitational forces and orbital motion
create these lrangee points and they're
labeled L1 through L5. Three of these
L1, L2, and L3 are considered unstable.
Small objects may be temporarily
captured near these points like the NASA
issa satellite SOHO at L1 or the James
Web Space Telescope at L2. But they have
to make corrections to their altitude
and course every 23 days to avoid
drifting out of position. Objects in
these unstable equilibrium points are
balancing on a metaphorical knife's edge
and any slight push from the solar wind,
radiation or the moon's gravity will tip
the balance. But L4 and L5, these
positions are stable. Unlike the other
Lrange points, these each make
equilateral triangles with the Earth and
Moon and are resistant to gravitational
pertubations.
Because of this, objects like asteroids
and dust tend to accumulate in these
areas. And that's where our story picks
up.
Cordelpski's observation of these
ghostly faint clouds in the L4 and L5
Lrange points originally named
liberation clouds but later known as
Cordeli dust clouds ignited a scientific
debate that has lasted for decades one
that is still going on to this day.
Immediately following his observation,
other astronomers, both professional and
amateur, attempted to locate these
supposed clouds. But for years, nobody
else could find them. At the time,
observational techniques were far less
advanced than today. Many astronomers
questioned whether these dust clouds
were real or merely optical illusions.
After all, detecting such faint
structures against the darkness of space
was a challenging proposition.
That skepticism persisted for years.
Every now and then, an astronomer would
catch a glimpse of a dust cloud in one
lrangee point or the other, and
sometimes clouds would be visible in
both locations. A few astronomers,
including Cordowski himself, captured
photographs of the clouds, but for
years, the dust clouds appeared so faint
in the photos that they could not be
reproduced in newspapers.
These photos aren't like photos we're
used to either. Images of these dust
clouds have to be taken using
photometric techniques, which involves
glass photographic plates with long
exposure times to capture the faint
lights of distant celestial objects.
They aren't of Hubble telescope quality.
They serve more to identify changes in
light intensity. And this is what
astronomers would use as evidence of the
cloud's existence.
In 1966, NASA organized an airborne
observation mission from its Converair
9990 jet laboratory operating far from
city lights at an altitude of 12,000 m.
The astronomers on those four NASA
flights were able to identify Cordelia
dust clouds in both the L4 and L5 Lrange
points, even managing to photograph the
dust cloud at L5. The orbiting solar
observatory OSO6
also observed the clouds in 1966 and
subsequent work was published measuring
their brightness and size.
However, in 1976,
another astronomer named Sigfrieded
Aruza at the Max Plank Institute for
Astronomy used numerical simulations to
show that conditions were unfavorable
for dust to accumulate in the L4 area
and questioned whether or not these
clouds actually existed.
Most of the KDC skeptics believe that
the gravitational pertubation of the
sun, solar wind, and other planets have
too strong of a destabilizing effect on
the L4 and L5 Lrange points for KDC's to
be maintained. Additionally, radar
studies of the clouds around this time
had produced negative results, leading
many to believe there was nothing of
circumstance at Little Grange points.
These doubts were further reinforced in
1983 when observers using a 61 cm
telescope near Tucson, Arizona found no
such clouds in either L4 or L5.
Yet just a few years later in 1989,
the clouds were photographed again by
astronomer Vinyoski
from an astronomical observatory in the
Bastardada mountains in Poland. Vinyoski
observed the KDC's to be a few degrees
in apparent diameter. These were also
the first three color phototric
observations of the clouds and they
revealed that the clouds appeared much
redder than the counterglow which is the
sunlight that gets scattered by the
general dust particles in space. This
observation suggested that the dust in
the KDC's is significantly different in
composition to the other local space
dust. Which begs the question, where are
these apparations coming from?
But then once again, the existence of
KDC's was brought into question when in
1991 the Japanese heightened space probe
did one loop around the L4 and L5
forrange points in an attempt to detect
dust particles, but didn't manage to
find any. However, astronomers say that
this should not be taken as evidence
against the dust clouds, as he highen
was only able to do one loop around each
Lrangee point. And if the clouds do
exist, the dust was likely moving too
slowly for it to be picked up by
Heiten's dust detectors. So, as you can
see, the scientific debate that begun in
1961 after Cordel's initial observation
is one that has continued through the
decades.
But now scientists seem to have made a
breakthrough. In 2018 and 2019,
astronomer Udit Slisbalo and physicists
Gabbor Hvath and Andreas Bart were able
to present clear evidence of the L5 KDC
by examining how the dust creates
patterns of scattered polarized light.
To do this, they use a type of
photography called polarized imaging,
which uses a series of filters that can
show light bouncing at specific angles.
When light hits these dust particles, it
scatters differently depending on the
specific composition and arrangement of
the particles, offering clues to the
nature of the clouds. After collecting a
series of images through various
polarized filters, the scientists found
that the patterns of polarized light in
the images matched theoretical
predictions for what we would expect to
see from sunlight that were scattered by
dust clouds. What's more, in their 2018
paper on the observations, they said
that in fact these results meant that
the scatters cannot be anything other
than dust particles. To back up these
observations, they were able to further
understand the formation of the clouds
at L5 through the use of computer
simulations. They calculated the motion
of 1.86 million dust particles to see
how dust in that region of space might
behave and found that under the right
conditions, that dust could get trapped
at the L5 point and remain there for a
long time. The result of these
simulations were dust clouds that
mirrored the shape and size of what had
been observed by the polarized imaging.
Very small particles spread over a large
area.
So what is going on here? Why could some
astronomers see these dust clouds and
photograph them while others claimed
they didn't exist at all? The answer may
lie in the structures themselves.
Despite spanning roughly 100,000 km by
70,000 km, which is almost nine times
wider than the Earth, the total mass of
the dust clouds is supposedly extremely
small. Not to mention, the particles
themselves are likely micron or
submicron sized, a similar size to many
bacterial cells. According to
observations from the polarized imaging
of L5,
a micron is already a very tiny
measurement at 1 millionth of a meter.
Individual particles of this size are
only visible through a powerful
microscope.
Not only are the KDCs composed of these
micron or submicron dust particles
sparsely spread across a wide area and
nearly invisible to the naked eye, but
the recent models made by Slbalo and
Horvath in 2018 suggest that the shape
of the L5 dust cloud also appears to be
dynamic. The models point to the
structure being nonuniform with dust
particle density varying across the KDC
and changing over time in synchrony with
the moon's orbital period.
This could also support the idea that
KDC's are not a stagnant accumulation of
dust, but rather that they may be
continuously losing and refreshing their
contents. kind of like an ever evolving
dust storm rather than a fixed stable
cloud. Things like solar wind or
gravitational pull from the sun or other
planets may disrupt the delicate
equilibrium that holds together these
dust clouds, causing them to disperse
before reforming again.
This combination of extremely tiny
particles that are dispersed over a
large area and the possibility that
these clouds may form, disperse, and
reform again and again over time could
help to explain the discrepancy in
observations over three decades.
However, the tentative confirmation of
the L5 KDC in 2018 still leaves open
scientific debate as to whether these
clouds exist continuously or whether
they appear and disappear depending on
the influence of the sun and other
planets.
Plenty of questions remain about cordfki
dust clouds, but one thing is certain,
these observations are not just a
mirage, but a real phenomenon within our
Earth moon system. Even though aspects
of their structure, evolution, and
composition remain under investigation,
there is broad acceptance that KDC's are
worthy of further study.
While these so-called ghost moons that
orbit the Earth moon lrange points may
seem otherworldly, our planet is no
stranger to additional moons. In fact,
Earth has had several mini moons and
quasi moons before, albeit very
different from the KDC's. For one thing,
mini moons typically come and go within
a year, while the gravitational traps or
lrange points, which are theorized to
cause these cordleski dust clouds, have
existed since our Earth moon system
formed, making the KDC phenomenon
potentially billions of years old.
Another distinct difference is that mini
moons and quasimoons are solid objects
whereas dust clouds are of course clouds
of loose dust.
Quasimoons get their name because from
one vantage point they look as if they
are true moons orbiting the earth.
However, with a wider view, these turn
out to be asteroids orbiting the sun.
Mini moons, on the other hand, are
objects that rarely orbit a planet. They
tend to be quite small and difficult to
detect, which is probably why we've only
ever managed to identify four mini
moons, none of which are orbiting Earth
anymore. Take for example the mini moon
called 2020 CD3, which I discussed in a
previous video. This small natural
satellite was captured in Earth's orbit
between January 2019 and May 2020,
temporarily giving our planet a second
moon. Well, mini moon. In my opinion,
our planet's possible ghost moons are
perhaps the most exciting of these
obscure types of moons because of how
unique they are.
Despite being dynamic structures, these
dust clouds are a long-term feature of
our Earth Moon system, and we still have
so much to learn about them. Observing
these dust clouds has tested the limits
of our observational abilities. And as
our technology and science improves, so
can our understanding of KDC's. We
should aim to build up more observation
data of the L4 KDC. as this feature is
historically under represented compared
to the cloud at L5. We could also
reservey the clouds using methods like
radar to see if technological
improvements can yield different results
compared to the negative detections of
the past as this would further establish
the presence of these elusive features
and fend off any lingering skeptics. But
now that they've been broadly accepted
by the scientific community, future
research can begin to explore how KDC's
are replenished over time, their
potential impact on space weather, and
their influence on satellite operations.
Whether KDC's exist continuously or
appear and disappear over time, at least
now we know that something really is out
there and we can study them with the
right focus. These ghostly dust clouds
continue to haunt our skies, reminding
us that even the faintest spooky traces
of cosmic apparitions can hint at
something palpable and is worth
investigating.
When 15 supernova go off close together,
both in time and proximity, it makes
quite a bang. It should be of no
surprise that such a violent event
should fundamentally transform the
region of space around where it
occurred. Interstellar dust was swept
aside from the forces of those
concurrent blasts, creating a monumental
void of low density matter and a shock
wave that continues to hurtle across the
galaxy to this day at a rate of 6 km a
second. In its wake, plasma reaching 1
million degrees C in temperature. This
simultaneous Swiss cheesing and heating
up of the interstellar medium is what is
now called a hot bubble and represents
both the end of stars and their
beginning. But this is not some distant
structure that lurks in a far away
corner of the universe. Our solar system
isn't even heading right towards it. We
are in it charging for its point of
origin head first.
Welcome to our local hot bubble. What
scientists now realize is the local
environment that exists around our solar
system. It is a neighborhood we are
still exploring, but its nature is
becoming clearer and clearer. So, what
do we know about the local hot bubble?
How did it form? And what more is there
to be discovered?
I'm Alex Mccoan and you're watching
Astramm. Join me today as we walk in the
aftermath of exploding stars and discuss
how scientists even determined we were
in the heart of a cataclysm to begin
with.
The local hot bubble was not always
something we knew about. First
identified in the 1970s from
observations of low energy X-ray
emissions that were detected over the
entire sky, the local hot bubble was
hypothesized to be a large cavity in the
interstellar medium called a superbubble
filled with tenuous million degree low
density gas.
In the 1990s, scientists found that
X-ray emissions could happen anywhere
neutral atoms interacted with the solar
wind, challenging the idea that the
emissions must point to a large hot
bubble. But soon, evidence would reveal
that the hypothesis from decades earlier
was indeed correct.
In 2014, NASA confirmed the existence of
the LHB through the diffuse X-ray
emission from the local galaxy mission
known as DXL.
While soft background radiation can come
from other sources, like from comets,
for example, the mission found that only
40% of the fog of low energy X-rays came
from within our solar system. This
affirmed that the dominant source was
diffuse X-ray emissions emanating from
the millionderee region of interstellar
plasma known as the LHB.
Although this confirmed the bubble,
questions remained about what could
create such a massive void and what
might explain the thousands of
surrounding young stars. The prevailing
answer proved to be both violent and
fascinating.
Recent research suggests that the local
hot bubble was the aftermath of around
15 supernova explosions that occurred
sequentially within a span of a few
million years, erupting in relatively
close proximity to one another.
Scientists estimated that the first of
these massive stellar explosions went
off roughly 14 million years ago, each
expelling enormous amounts of energy,
pushing out the surrounding interstellar
material and heating the remaining gas
to extreme temperatures.
Evidence of these ancient explosions has
been preserved in our Earth's geological
record in deep sea sediment deposits in
the form of a special isotope called
iron 60. This radioactive isotope can
come from a few different sources, but
the most common source of iron 60 is
believed to be supernova explosions.
We know that the source of the isotope
is extraterrestrial because the earth
itself has no way of producing iron 60
on its own and matching deposits have
been found on the moon as well. The
reason that this radioactive isotope is
special is because we know how long its
half-life is. We know that it decays
into cobalt 60, another radioactive
isotope, before it finally decays into
nickel 60, a stable element.
Iron 60 has a halflife of 2.6 million
years and cobalt 60 has a fairly short
halflife of just 5.3 years. Because of
this, when we find a deposit that
contains these elements, scientists can
compare the amounts of iron 60, cobalt
60, and nickel 60 like an elemental
clock to reveal when that material was
deposited on our planet. And luckily for
us, international research teams have
found several such deposits over the
last couple of decades.
In 2016, iron 60 deposits were found in
deep sea crust samples taken from the
Pacific, Indian, and Atlantic oceans,
indicating two distinct spikes in the
radioactive debris that pointed to
several supernova events in the
notsodistant past. And not too far from
our solar system, just 326
lighty years away, the sample showed a
spike of iron 60 between 3.2 and 1.7
million years ago, and another spike
between 6.5 and 8.7 million years ago.
Nuclear physicist Anton Walner, who led
one of these research teams studying the
deposits, said that the fact that the
more recent debris was spread across 1.5
million years, suggests that there were
a series of supernova that occurred one
after another in close succession.
Astrophysicist Dieter Breitvert who led
a second team of scientists identified a
likely source of these supernova
explosions which would have occurred 196
to 423 lighty years from the sun.
These supernova that created our local
hot bubble may have been part of an
aging star cluster whose surviving
members are now associated with the
Scorpius Centura stellar group. Using
the iron 60 deposits, the team was able
to trace the signals of two supernova,
one that happened 1.5 million years ago
and the other 2.3 million years ago as
the result of the deaths of stars that
were 8.8 times and 9.2 times the mass of
our sun, respectively.
In fact, our LHB is still growing today,
albeit much more slowly than when the
supernova exploded millions of years
ago. The speed of expansion has
plateaued at about 6 km/s now, according
to astrophysicist Katherine Zucker. In
2022, Zucker authored a groundbreaking
paper that reconstructed the evolution
of our galactic neighborhood, tracing
the chain of events that created our
local hot bubble and led to the
formation of all the young stars we see
nearby today. From there, they made an
incredible discovery.
Using data from the European Space Ay's
Gaia telescope, Zucker and her team were
able to construct a 3D space-time map,
showing that within 500 lighty years of
our planet, all of the young stars and
star forming regions reside on the
surface of our local hot bubble. With
these 3D positions and the 3D motions of
the stellar clusters, they traced back
20 million years of star formation
history near our local hot bubble. The
implications were clear that all of the
well-known star forming regions near our
solar system had formed along the outer
edge of the local bubble as it swept up
gas during its expansion.
Stella nurseries are a field we are
learning more about all the time.
particularly as new images are taken by
our telescopes. Here's a spectacular
image of the Chameleon 1 dark cloud, one
of our nearest stellar nurseries taken
by a dark energy camera on the Victor M.
Blanco 4 m telescope at Cherro Talo
Interamerican Observatory. By studying
the propagation of starlight from within
it, scientists can tease out details
about how stars form, which might help
us better understand the local hot
bubbles impact on our galaxy today. You
might not have seen this particular
image before as new space news is coming
out all the time, but I've talked about
it in my newsletter, which I've recently
launched to help you keep up with all
the breathtaking photos released by our
many telescopes on Earth and in orbit,
or new breakthroughs that reshape how we
understand the cosmos. You should sign
up to never miss the most exciting news,
even if the headlines do, by following
the link in the description below. There
are new editions that come out every
Thursday.
From the local hot bubbles birth 14
million years ago, Zucker and her
colleagues identified four epochs of
star formation on the bubble shell.
Starting about 16 million years ago, we
see the birth of the upper centurus
lupus or the UCL star cluster, followed
by the lower centurus crux or LCC star
cluster.
These formed about 49 light years apart
from one another and about 14 million
years ago. These stellar populations
were the source of the stars that went
supernova to create our local bubble.
About 10 million years ago, we see the
first of the four star forming epochs
after the formation of the LHB. The
upper scorpius association and older
afucuca stella populations are born in
the first epoch. 6 million years ago the
second star forming epoch formed Corona
Arralis and the older stars of Taurus.
Then around 2 million years ago the
stars in Lupus and Chameleon as well as
younger stellar populations of Taurus
and ofucus came to be in the third
epoch. And finally, our present time
falls within the fourth star forming
epoch. We can observe the dense star
forming molecular gas that surrounds the
LHB, which will eventually lead to more
star clusters being born along the
bubble's outer edge.
With all of this stellar creation, you
might be surprised to learn that we are
interlopers. Our sun did not form inside
the local bubble. In fact, the sun was
about 978 light years away when the
first supernova went off in UCL and LCC,
only joining up with the LHB about 5
million years ago as its path through
the galaxy took it into the bubble. With
the trajectory shown in yellow dots, you
can see our sun's location just before
it entered the bubble. And now, just by
coincidence, our sun happens to be
located near the center of the LHB.
Drifting into the heart of what was once
a raging furnace, scientists became
interested in mapping out the ongoing
temperature within the local bubble. You
might wonder why we're so calm if
temperatures of plasma here can reach 1
million° C.
The key lies in that plasma's density.
Look, this 3D map from Zucker's 2022
publication shows our local hot bubble
in dark blue. The density inside our
bubble is extraordinarily low,
containing about 100 times less hydrogen
than the typical interstellar medium. So
while the temperature of this gas
soarses to around 1 million° Kelvin,
giving rise to the diffuse X-ray
emissions we have observed around the
whole sky, we don't have much to worry
about.
Tracking temperatures within the local
bubble has provided more evidence of its
existence. The extended renen survey
with an imaging telescope array, better
known as the e-roisa x-ray telescope,
has been able to gather the most
detailed all sky survey of soft x-rays
to date. And that data has been used to
map the LHB and our solar neighborhood
in much more detail than before.
launched aboard the joint Russian and
German mission Spectrum Renen Gamma or
Spectre RG in 2019. Data from the E
Rosita X-ray telescope has allowed a
team of scientists led by the Maxplank
Institute for Extraterrestrial Physics
to create a 3D map of the LHB and
identify a temperature gradient where
the galactic south was slightly hotter
than the galactic north.
This temperature dichotomy could be
explained by supernova explosions in the
past few million years. And by creating
this bubble map, the team also found
that the LHB is stretched out towards
the poles of the galactic hemisphere.
This is because the hot gas in the
bubble expands out in the direction with
the least resistance, which happens to
be away from the Milky Way's galactic
disc. Along with identifying temperature
variations and the shape of the bubble,
the team compiled this and other data to
create an even more detailed map of our
galactic neighborhood. In the new 3D
map, our local hot bubble looks like a
three-dimensional splatter surrounded by
and even overlapping other galactic
structures. These other structures
represent known supernova remnants like
the Gum Nebula shown here in red and
dense molecular clouds shown here in
orange.
With the new data and 3D maps, these
super bubbles seem likely to be common
in our galaxy, creating a Milky Way
that's sort of like Swiss cheese. The
cavities of our Swiss cheese galaxy are
blasted out by gigantic supernova
explosions with new stars forming along
the edges of the holes created by dying
stars. And like Swiss cheese, it appears
that some of these super bubbles may
have tunnels connecting them to other
bubbles or other structures, suggesting
our local hot bubble could be part of an
intricate network of similar features
throughout our galaxy. For example, we
have the Canis Majorus Tunnel, which
lies on the Milky Way's galactic disc
and is believed to connect our local hot
bubble to the Gum Nebula, or another
larger nearby superb bubble. But the 3D
map also revealed another previously
unknown interstellar tunnel stretching
towards the constellation Centurus,
possibly connecting our local bubble to
the neighboring Loop One super bubble.
While these interstellar tunnels are
tantalizing, our current understanding
of them is limited. Nevertheless, these
tunnels of hot gas and bubbles of star
formation shaped by the death of
gigantic older stars has me in awe of
how powerful and interconnected the
evolution of our local galactic
neighborhood really is. It suggests that
stars are not just born and die in
isolation, but that their energetic
output continues to mold the environment
for millions of years after their
demise.
And as our observational tools become
more sophisticated, we are beginning to
uncover the extent of these hidden
structures.
So next time you look up at the night
sky, you might remind yourself that we
are surrounded by crazy patterns. just
like our local bubble in the Milky Way
that was carved out by ancient
cataclysms. And that some of those stars
that you see are actually plastered
along the walls of a supernova blasted
cavity which connects to other parts of
the galaxy through interstellar tunnels.
Wow.
In 2022, this astonishing image was
published. What makes it so astonishing?
Well, this is one of the most detailed
radio images of the center of our galaxy
that's ever been produced. Assembled
from the first survey using the full
array at the MCAT radio observatory in
South Africa. This image took three
years of data analysis to complete and
it is revealing something thoroughly
bizarre. Deep within the turbulent chaos
at the center of the Milky Way are
hundreds of highly ordered
one-dimensional filament-like structures
dangling inexplicably above and below
the galactic center. These enigmatic
filaments stretch for up to 150
lightyear yet are only one to three
lightyears across. The big question is
what are these strange superersized
strands?
Now scientists are trying to unpick this
mircat image to work it out. I'm Alex
Mccoan and you're watching Astramm. Join
me today as we uncover the mysteries
around one of the Milky Way's weirdest
phenomena. We'll explore the happy
accident that led to their discovery and
the extreme characteristics that are
leaving scientists baffled.
The center of the Milky Way, 27,000
light-years from Earth, is a place of
violence.
This innermost region, the central
molecular zone, spans 1,600 light-year
and is by all accounts the most extreme
part of our galaxy. Density,
temperature, and turbulent velocity, a
measure of chaotic fluid motion, are
around 1 to two orders of magnitude
higher here than anywhere else in the
galaxy. The cosmic ray energy density, a
proxy for energetic activity, is 2 to
three orders of magnitude higher.
This region is home to vast complexes of
molecular gas, about 20 million solar
masses worth, dense cosmic clouds,
ionized plasmas, extreme cosmic ray
energy, ultraviolet and x-ray radiation,
and turbulent magnetic fields. It is a
hotbed of cosmic activity from the
formation of stars to exploding
supernova. And let's not forget
Sagittarius a star, the super massive
black hole 4 million times the mass of
our sun at the very center of it all.
These conditions are hugely exciting for
astronomers, but they make the galactic
center notoriously hard to image.
Visible light can't penetrate the dense
clouds of dust and gas. So researchers
turned to other parts of the
electromagnetic spectrum to lift the
veil and reveal the secrets at the heart
of the galaxy.
Radio waves have the longest wavelengths
of the electromagnetic spectrum from a
few millime to hundreds of kilome and
the wavelengths in the range of millime
to tens of meters are ideal for radio
astronomy. They pass through the
obscuring clouds of gas and dust, giving
us a clear view of what lies beneath. In
the early 1980s, Furhad Ysef Zade
studying for his PhD was using the very
large array telescope in New Mexico to
produce a radio map of a section of the
galactic center. He was planning to
study star forming regions, but narrow
strips of radio emission were streaking
across the entire survey area right
through the parts he was interested in.
He thought they must be artifacts in the
data or imaging errors, which any
scientist will tell you is highly
annoying. So after much frustration and
no luck resolving the problematic
artifacts, he returned to the VA to
image again at another frequency. And
that was when his Eureka moment struck.
At 400 a.m. one morning, he was
comparing the two samples taken at
different times using different
wavelengths, and he saw the same
structures in both images.
This was no artifact. This was a very
real finding, something unlike anything
he or anyone else for that matter had
come across before.
Zade was seeing highly ordered
structures where previously only chaos
was thought to exist and they had some
very unusual features. Most striking was
their vast scale. These were continuous
narrow strips of radio emission 50 to
100 light-years long, but only 1 to
three light-years wide, dangling
vertically above and below the central
molecular zone, the most extreme part of
the Milky Way.
Some appeared in pairs or clusters
running parallel to each other like
strings on a harp, each separated by a
standard distance of around one
astronomical unit, the distance between
Earth and the Sun. When he cross-cheed
them with the infrared data from that
area, Zarde also discovered they had no
counterpart in that area of the
spectrum. This told him they were
non-therrmal emissions. That is to say
they were not produced by heated gases.
This was corroborated by other
measurements such as spectral index and
polarization which showed that the
filaments were highly magnetic and
emitting synretron radiation.
Synretron radiation occurs when
electrons moving near the speed of light
interact with a strong magnetic field.
which begged the question, what on
Earth, or should I say not on Earth, was
accelerating the electrons to such
speeds. The emissions along the length
of the structures were continuous,
ruling out localized events like star
formation or supernova remnants. So,
Zade dubbed them non-therrmal filaments
and suggested they were likely related
to galactic scale phenomena. His
observations didn't correspond to
anything else in the known galaxy. And
Zarde had many more questions. Where did
the non-thermal filaments come from?
What was maintaining their linear
structures over such vast distances of
space and time? Why, when clustered,
were they so evenly spaced?
But almost as soon as this startling
discovery was made, the trail started to
go cold. The available telescopes at the
time simply didn't have the sensitivity
needed to provide answers.
Over the next 35 years, only a handful
of other vertical non-therrmal filaments
were revealed and categorized. Some were
even given inigmatic names like the
snake, pelican, and bent harp. Sadly,
there wasn't enough data to make any
great leaps forward in understanding.
Well, not until 2022. And Miaat's
mindblowing image.
The Miaat radio telescope at the South
Africa Radio Astronomy Observatory or
SARo is comprised of 64 interlin
antennas each with a 13.5 m diameter
parabolic dish spread over 8 km of radio
silent zone. Built over four years, the
full array was inaugurated in 2018.
Its location in the southern hemisphere
is perfect for imaging the center of the
Milky Way thanks to our sun's axle tilt
relative to its own position in the
galaxy. So, Miaat has a direct line of
sight into the CMZ and the galactic
center. Over the course of 3 years, an
international team led by Dr. Ian
Haywood and including Zarde, now
professor at Northwestern University,
directed Mia Cat to a 6.5 square degree
portion of the galaxy, a section of the
sky around 30 full moons wide with
Sagittarius A star right in the middle
using Lband radio frequencies of 856 to
1,712 MHz, equivalent to wavelengths of
18 to 35 cm. They split this area into a
20part mosaic, directing the telescope
to survey each tile in turn over a total
of 144 hours on target. This was the
first time Mircat's full array was used
with 60 to 62 dishes sampling the sky at
any one time. After generating 70
terabytes of raw data, the equivalent to
700 hours of 4K YouTube content, the
team then had to process it. That was no
mean feat. Given the complexity of the
environment, they needed to put the data
through a highpass filter using a method
called difference of Gaussians. This is
a commonly used edge smoothing technique
to remove background noise and enhance
the visibility of fine structures,
especially important for visualizing
non-therrmal filaments. And this is the
result.
More like a work of art than a
scientific study, it captures a wealth
of features. Some are wellnown like
Sagittarius A star seen in the central
saturated area here and clearer views of
previously known supernova remnants and
star forming regions. This here is a
supernova remnant. To its left is a
runaway pulsar, the mouse and up on the
right one of the longest and most famous
non-therrmal filaments, the snake.
As noted by the team, one of the most
startling discoveries was the sheer
number of filaments apparent in the
image, an order of magnitude greater
than all previously known, most of which
had never been seen before.
This was game-changing for Zard and his
colleagues. Now we finally see the big
picture. A panoramic view filled with an
abundance of filaments. He said this is
a watershed in furthering our
understanding of these structures. There
was finally enough data to carry out
meaningful population studies. They set
to work carrying out statistical
analysis of the filaments. This work
published in the astrophysical journal
letters not only further categorizes the
filaments but gives tantalizing clues to
their origin. The new data confirmed
that all of them are magnetized.
In fact, the team found that the
magnetic field was significantly greater
in some cases up to 10 to 100 times
stronger than typical galactic magnetic
fields. The new analysis also confirmed
that synretron radiation is a defining
characteristic.
Interestingly, the MICAT data revealed
that there is a steepening with galactic
latitude. In other words, the filaments
appear to cool as they stretch away from
the galactic plane. This gives us a clue
as to their possible origin. The
electrons further away from the galactic
plane could be older, implying that the
filaments are related to past activity
of Sagittarius a star. And there was
another clue that suggested this too.
Enormous structures known as radio
bubbles. First discovered by Haywood
Zade and the Miacat team in 2019, these
huge radio emmitting structures stretch
symmetrically above and below the
galactic plane, forming an hourglass
shape thousands of light years across.
They are thought to have been created by
a phenomenal outburst from Sagittarius a
star about 100,000 to a million years
ago. An event powerful enough to leave
such a scar on the galaxy could have
been vast quantities of gas and dust
falling into the black hole or a huge
and sudden burst in star formation close
by. An incident like this would have
triggered an intense outburst of energy
and whipped up galactic winds, driving
gas and cosmic rays violently away from
the galactic center, stretching and
amplifying magnetic field lines in its
wake, creating those bubbles and
non-therrmal filaments. What's more,
strong magnetic fields, which as we now
know are a confirmed characteristic of
all filaments, capture cosmic rays. And
the great thing is we can date them.
Those detected in the filaments by a
mircat match the proposed period of the
Sagittarius A star outburst considered
responsible for the radio bubbles. In
other words, they are the same age.
The position and capabilities of Mircat
alongside the same highpass filtering
used to resolve the non-therrmal radio
filaments not only revealed these
bubbles in astonishing detail but showed
almost all of the filaments are confined
within them. This close physical
association adds even more weight to the
argument that the same energetic event
created them. Something powerful enough
to create the bubbles would certainly be
able to accelerate electrons to near the
speed of light with the stretch magnetic
field lines channeling them to produce
the filament's signature synretron
emission. With this hypothesis in mind,
Zard and the team described the
formation of non-therrmofilaments as
magnetized streamers in a cosmic
raydriven wind. It certainly paints a
compelling picture for the possible
origin of the filaments, but it is by no
means conclusive as even the authors
themselves attest. Other theories are
being worked on. With a mystery this
tantalizing, other astronomers have been
studying the filaments, too. But this
single image is still the one that's
told us the most. Zard wasn't kidding
when he said it was a watershed moment.
But with so many unanswered questions,
some going back 40 years, where does
that leave us? Are non-thermal radios
merely a galactic curiosity?
Not by any means. They are a riddle
wrapped in a mystery inside an enigma
and could shed light on one of the
biggest unanswered questions out there.
How super massive black holes regulate
star formation within a galaxy.
Scientists know that the active centers
of galaxies must transfer energy and
matter into interstellar space through a
process called galactic feedback. If
they didn't, star formation would run
away unchecked, using up a galaxy's gas
and dust faster than observations tell
us. But how this feedback happens is
unknown. Mircat's detailed imagery of
non-therrmal filaments and the radio
bubbles provides us with compelling
evidence that this outflow of energy
could happen in discrete but powerful
outbursts and this is something that has
been seen before.
Fermy bubbles discovered by NASA's Fermy
gammaray telescope in 2010 are even
bigger hourglass shaped configurations
spanning a total of 50,000 lightyear.
These mindbogglingly massive structures
colored magenta in this image are
thought to be millions of years old.
Likely caused by a violent outburst from
Sagittarius A star, which calculation
suggests had the energy of 100,000
supernova.
This is much more powerful and ancient
than the event proposed to have made the
filaments and radio bubbles. But
together they paint a picture of
intermittent outbursts from deep within
the heart of our galaxy. Both have the
potential to regulate star formation,
ensuring that the Milky Way doesn't
suffer from burnout. As scientists
continue to unravel the mysteries of
non-therrmof filaments and tackle the
big questions about how the universe
works, the trail doesn't seem to be
going cold again anytime soon. Since the
first full array image, Mircat has found
more of these mystery strands in other
galaxies with very similar properties to
the ones we see in the Milky Way. Their
very existence elsewhere suggests a
common underlying mechanism that alludes
to their role in fundamental galactic
processes.
To conclusively piece together the whole
picture will require another step change
in imaging resolution. And hopefully
that's not too far off as MICAT already
awarded by the Royal Astronomical
Society for its spectacular observations
in radioastronomy was built with
longerterm goals in mind, namely to be
incorporated into the square kilometer
array. With a total collecting area of
one square km, it will be 50 times more
sensitive than any other radio
instrument in existence. and it's
expected to be fully constructed by
2028. Keeping an eye on developments in
other parts of the electromagnetic
spectrum will be important too. Zard
believes that the next breakthrough will
come from gamma ray telescopes. Imaging
at higher frequencies results in higher
resolution imagery which has potential
to show us whether the filaments, the
radio bubbles that contain them, and the
vast fermy bubbles are connected.
There's an elegance in order rising out
of chaos and observing non-therrmal
filaments streaming out through the
cosmic winds certainly fits that notion.
So, keep watching this space. And with
images and phenomena this spectacular, I
certainly have no problem doing that.
If you've been following the Astramm
Answer series recently, you'll notice
that we've talked a lot about how the
universe is structured.
filament structures of galaxies being
pulled apart by the universe's expansion
with bubbles or voids forming in the
gaps.
Because of the universe's expansion,
everything is moving away from
everything. But of course, this isn't
totally true in practice due to a
mysterious force called gravity.
Gravity is a pulling force or
technically it is the curvature of
spaceime caused by uneven distribution
of mass.
On very small scales, gravity is hardly
relevant at all. I don't feel any pull
towards objects around me, only towards
the earth because it is so massive.
Celestial objects close enough to the
sun are most influenced by its gravity.
And all stars in the galaxy orbit around
a super massive black hole at the
galaxy's core. But it doesn't stop
there. You've probably heard that the
Andromeda galaxy is hurtling towards us.
How can that be when everything is
moving apart?
Gravity.
Objects that are close enough together
with a large enough mass are pulled
towards each other by gravity faster
than the universe can expand.
This is why we have galaxy
superclusters. And in fact, we are part
of one. Gravity is keeping these galaxy
clusters bound together, meaning over
extremely large time scales, collisions
aren't totally unusual.
In fact, a new theory has recently been
proposed that the Milky Way may have
recently experienced a collision with a
large melanic cloud-sized diffused
galaxy called Antlia 2.
Scientists have discovered that the
Milky Way has ripples consistent with it
having had a collision in the past, but
we couldn't pinpoint what it collided
with until Gaia discovered the Anier 2
galaxy hidden behind our galactic disc.
This makes it very hard to spot as
although it is massive, it is very
spread out due to the collision and
being behind our galactic disc makes it
hard to see due to the stars and dust in
the way. But that brings us on to the
main topic of this episode, the great
attractor.
In an opposite vein from the supervoids
video, where there are regions of space
where there is an almost total absence
of mass for hundreds of millions of
light years in any direction, the great
attractor is the biggest concentration
of mass for hundreds of millions of
light years. It is so massive that even
though our galaxy is between 150 to 250
million lighty years away, we and all
galaxies around it are currently moving
towards it. Estimates put its mass at
roughly 1,000 trillion suns, which is
enough for many thousands of galaxies.
But what could possibly be there that is
that massive?
Well, for the longest time it was a
total mystery because like Adlia 2, the
region where the great attractor is
located is hidden behind our galaxy's
disc. However, X-ray telescopes can see
through the disc. And recent
technological improvements and advances
in X-ray telescopes have meant that we
have been able to detect thousands of
galaxies in the region where the great
attractor is supposed to be. But the
mass detected didn't add up. There
wasn't enough present to create such a
pull. Further analysis has revealed
something very interesting that while we
are being pulled towards the great
attractor, there is something even more
massive behind it. Located 650 million
lighty years away called the Chappley
attractor or the Shappley supercluster.
Located there are many thousands of
galaxies densely packed together with a
mass of 10,000 trillion suns and
everything within 1 billion lightyear is
being pulled towards it. On the other
hand, looking the opposite direction
from the Shappley supercluster, we see
an underdent region where everything
seems to be moving away from it called
the dipole repeller.
It isn't actually repelling mass, but
due to all the mass around it being
pulled towards more dense regions by
gravity, it creates the illusion that it
is repelling that mass. Although there
are some scientists that do claim that
an unknown repelling force is at work
there.
Simply put, we are still in very early
days when it comes to understanding the
universe.
We do observe certain things like the
motion of galaxies, dense galaxy groups
and absences of galaxies in large voids
or repelling regions. We observe the
expansion of the universe and observe
the filamentary structures. But the
universe is an impossibly large place.
We can only see so far, only live so
long. Plus, our technology is limited.
We have theories which try and explain
what we see. But I really wouldn't be
surprised to see these theories change
as more data becomes accessible. Some
may ask what's the point then? However,
I for one am hugely grateful for the
bright minds working on this as
discovering our place in the universe is
so fascinating. I'm glad humans have an
insatiable need to explore and
understand everything around them. This
innate sense of wonder and curiosity is
what drives the evolution of mankind,
and I am excited to witness it.
A massive thank you to our astronauts on
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it was still made possible thanks to the
hundreds of members we have there. Link
is in the description to join our
growing community. Patreon is where
Astramm truly takes shape. A place for
people who love space, who want to see
these videos keep improving and reaching
more curious minds. Every new member
keeps the channel focused on what really
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available to everyone. If you enjoy what
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