Astrum Space - We Found a Giant Structure In Space and We Don’t Know What It Is
Episode Date: February 24, 2026This Astrum compilation explores the mysterious and baffling structures astronomers have found in space. From massive megastructures to ghostly spectres following our planet, we explore the cosmic str...uctures that defy explanation. ▀▀▀▀▀▀Astrum's newsletter has launched! Want to know what's happening in space? Sign up here: https://astrumspace.kit.comA huge thanks to our Patreons who help make these videos possible. Sign-up here: https://bit.ly/4aiJZNF
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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 McColigan and you're watching Astrum. Today we're in
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 Kazimierz Kordolevsky 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 Lagrange points of our Earth Moon system.
In case you aren't familiar with Lagrange points, let me quickly explain.
The grange points are positions in space where the gravitational forces of two large bodies
are balanced by the centripetal 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.
Lagrange points were named after the Italian French astronomer and mathematician Yosef Louis
Lagrange, after he published a prize-winning paper about this phenomenon in 1772.
While we're going to be talking about the Lagrange 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 in the Sun.
In any two body system, there are five spots where gravitational forces and orbital motion
create these Lagrange 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-ESA satellite
Soho at L1, or the James Webb 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 Lagrange points, these each make equilateral.
triangles with the Earth and Moon and are resistant to gravitational perturbations.
Because of this, objects like asteroids and dust tend to accumulate in these areas, and that's
where our story picks up.
Kordaevsky's observation of these ghostly faint clouds in the L4 and L5 Lagrange
points, originally named Liberation Clouds, but later known as Kordolevsky 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 the 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 Lagrange
point or the other, and sometimes clouds would be visible in both locations.
A few astronomers, including Kordelevsky himself, captured photographs of the clouds.
But for years, the dust clouds appeared so faint in the photos.
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 Conver Air 990 Jet Laboratory,
operating far from city lights at an altitude of 12,000 meters.
The astronomers on those four NASA flights were able to identify Kodolevsky dust clouds
in both the L4 and L5 Lagrange 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 Siegfried Ruzer at the Max Planck 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 perturbation of the sun, solar wind, and other planets have too strong of a destabilizing effect on the L4 and L5 Lagrange points for KDCs 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 the Lagrange points.
These doubts were further reinforced in 1983, when observers using a 61-centimeter 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
Vinyaski.
From an astronomical observatory in the Biestada Mountains in Poland, Vinyaski observed
the KDCs to be a few degrees in apparent diameter.
These were also the first three-color photometric observations of the clouds, and they revealed
that the clouds appeared much redder than the counterglo, which is the sunlight that gets scattered
by the general dust particles in space.
This observation suggested that the dust in the KDCs 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 KDCs was brought into question, when in 1991
the Japanese Heighton Space Probe did one loop around the L4 and L5 Lagrange 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 Heighton was only able to do one loop around each Lagrange point.
And if the clouds do exist, the dust was likely moving too slowly for it to be picked up
by Heiton's dust detectors.
So as you can see, the scientific debate that begun in 1961 after Kordolevsky'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 Uditsliz Balo and physicist
Garbo Horvath and Andreas Barter 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 of the shape of the
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 kilometers by 70,000 kilometers, which is almost 9 times wide,
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 one millionth of a meter. Individual particles of this
size are only visible through a powerful micro,
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
Sliz Barlow 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 non-uniform, 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 KDCs 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 destroy
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 L5KDC 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 Kortolevsky dust clouds, but one thing is certain.
These observations are not just a mirage, but a real phenomenon within our Earth-moon system.
Though aspects of their structure, evolution, and composition remain under investigation,
there is broad acceptance that KDCs are worthy of further study.
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While these so-called ghost moons
that orbit the Earth moon at Grange 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 KDCs. For one thing,
mini-moons typically come and go within a year, while the gravitational traps, or Lagrange
points, which are theorized to cause these Kordelevsky dust clouds, have existed since our Earth-moon
system formed, making the KDC phenomenon potentially billions of years old. Another day,
A distinct difference is that mini moons and quasi-moons are solid objects, whereas dust clouds
are, of course, clouds of loose dust.
Quasi-moons 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.
Minim moons, on the other hand, are objects that really 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 KDCs.
We should aim to build up more observation data of the L4 KDC, as this feature is historically
underrepresented compared to the cloud at L5.
We could also resurvey 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 have been broadly accepted by the scientific
community, future research can begin to explore how KDCs are replenished over time, their
potential impact on space weather, and their influence on satellite operations.
Whether KDCs 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 faint
scientist, spooky traces of cosmic apparitions can hint at something palpable and is worth investigating.
When 15 supernovae 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 shockwave 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 Celsius in temperature.
This simultaneous Swiss cheesing and heating up of the interstellar medium is one of the interstellar medium,
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 faraway 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
is the local environment that exists around our solar system.
It is a neighbourhood 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 McColgan and you're watching Astrom.
Join me today as we walk in the aftermath of exploding stars and discuss how.
Now 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 super bubble 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
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 million-degree
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 their local hot bubble was the aftermath of around 15 supernova explosions
that occurred sequentially within a span of a few million years, erupting in the middle of
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 the
a special isotope called IN60. This radioactive isotope can come from a few different sources,
but the most common source of IN60 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 half-life of 2.6 million years, and Cobalt 60 has a fairly short
half-life 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 cross samples taken from the Pacific, Indian,
and Atlantic oceans.
indicating two distinct spikes in the radioactive debris, but pointed to several supernova
events in the not-so-distant past, and not too far from our solar system, just 326 light
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 Walsh.
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 supernovae that occurred one after another in close succession.
Astrophysicist Dieter Breitschvert, who led a second team of scientists, identified a likely
source of these supernova explosions, which would have occurred 196 to 423 light years.
from the sun.
These supernovae that created our local hot bubble may have been part of an aging star cluster,
whose surviving members are now associated with the Scorpius Centora stellar group.
Using the iron 60 deposits, the team was able to trace the signals of two supernovae, 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.
two times the mass of our sun, respectively. In fact, our LHB is still growing today, albeit much more
slowly than when the supernovae exploded millions of years ago. The speed of expansion has plateaued
at about six kilometers per second now, according to astrophysicist Catherine 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 Agency's Gaia Telescope, Zaka and her team were able
to construct a 3D space-time map, showing that within 500 light 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.
Stellar nurseries are a field we're learning more about all the time, particularly as new
images are taken by our telescopes.
Here's a spectacular image of the Chameleon One Dark Cloud, one of our nearest stellar nurseries,
taken by a dark energy camera on the Victor M. Blanco 4-meter telescope at Chero Tololo Inter-American
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.
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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 Centaurus Lupus, or the UCL
star cluster, followed by the lower Centaurus 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
the formation of the LHB, the Upper Scorpius Association, and older Ophiuchus stellar populations
are born in the first epoch.
Six million years ago, the second star-forming epoch formed Crona Australis 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 Ophiuchus, 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 son'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
degrees Celsius.
The key lies in that plasma's density.
Look, this 3D map from Zucker's 22 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 soars to around 1 million degrees Kelvin, giving rise to
the diffuse X-ray emissions we have observed around the whole sky, we don't have much.
much to worry about.
Tracking temperatures within the local bubble has provided more evidence of its existence.
The extended Rundgen survey with an imaging telescope array, better known as the E-Rosister
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, Renzhen, Gamma, or
Specter-RG in 2019, data from the E-Rosita X-ray telescope has allowed a team of scientists
led by the Max Planck Institute for Extrrestrial 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 disk.
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 connect
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 Majoris Tunnel, which lies on the Milky Way's Galactic
disk, and is believed to connect our local hot bubble to the Gum Nebula, or another larger nearby
super bubble.
But the 3D map also revealed another, previously unknown interstellar
tunnel, stretching towards the constellation Centaurus, possibly connecting our local bubble
to the neighboring Loop 1 Superbubble.
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 in the powerful.
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.
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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 MIRCAT 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 sense.
center.
These enigmatic filaments stretch for up to 150 light years, yet are only one to three light years
across.
The big question is, what are these strange, supersized strands?
Now scientists are trying to unpick this mere cat image to work it out.
I'm Alex McColgan and you're watching Astrum.
Join me today as we uncover the mysteries around one of the Milky Cat's.
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 years 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 one to two orders of magnitude higher here than anywhere
else in the galaxy. The cosmic ray energy density, a proxy for energetic activity, is two 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 supernovae.
And let's not forget Sagittarius A-star, the supermassive black hole four 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 turn to other
parts of their 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 millimeters to hundreds of kilometers, and the wavelengths in the range of
millimeters 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,
Fahad Yusif Zadeh, 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 solidly.
scientists will tell you is highly annoying. So after much frustration and no luck resolving the
problematic artifacts, he returned to the VLA to image again at another frequency. And that was
when his eureka moment struck. At 4 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 one 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-checked them with the infrared data from that area,
Zade also discovered they had no counterpart in that area of the spectrum.
This told him they were non-thermal 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 synchrotron radiation.
Synchrotron radiation occurs when electrons moving near the speed of light
interact with a strong magnetic field,
which beg 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-thermal filaments
and suggested they were likely related to galactic scale phenomena.
His observations didn't correspond to anything else in the known galaxy
and Zade 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-thermal
filaments were revealed and categorized. Some were even given enigmatic 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 Mirkatz's mind-blowing image.
The Mirat Radio Telescope at the South Africa Radio Astronomy Observatory,
or Saro, is comprised of 64 interlinked antennas, each with a 13.5-meter-parabolic parabolic
dish, spread over 8 kilometers 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, Miehkat has a direct line of sight into the CMZ and the galactic center.
Over the course of three years, an international team led by Dr. Ian Hayward, and including
Zade, now professor at Northwestern University, directed Mirkat 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 L-band radio frequencies of 856 to 1,000,
712 megahertz, equivalent to wavelengths of 18 to 35 centimeters, they split this area into
a 20-part mosaic, directing the telescope to survey each tile in turn over a total of 144
hours on target.
This was the first time Meerkat'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 high-pass filter using a method called
difference of Gaussian. This is a commonly used edge-smoothing technique to remove background noise and in high-passed
the visibility of fine structures especially important for visualizing non-thermal filaments.
And this is the result.
More like a work of art than a scientific study, it captures a wealth of features.
Some are well known, 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 runway pulsar, the mouse, and up on the right,
one of the longest and most famous non-thermal 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 Zade 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 astrophysicological,
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 synchrotron radiation
is a defining characteristic.
Interestingly, the mere cat 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 Hayward, Zadeh and the Miercat team in 2019, these huge
radio-emitting 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 amplify magnetic field lines in its wake,
creating those bubbles and non-thermal 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 Amirat 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 Mirat, alongside the same high-pass filtering used to resolve the
non-thermal 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
synchrotron emission. With this hypothesis in mind, Zaday and the team described the formation
of non-thermerements as magnetized streamers in a cosmic ray-driven 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. Zadr 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 radio filaments 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 supermassive black holes regulate star formation within a galaxy.
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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.
Mir Kat's detailed imagery of non-thermal filaments and the radio bubbles provides us
with compelling evidence that this outflow of energy could have.
happen in discrete but powerful outbursts.
And this is something that has been seen before.
Fermi bubbles, discovered by NASA's Fermi gamma-ray telescope in 2010, are even bigger.
Hourglass-shaped configurations spanning a total of 50,000 light years.
These mind-bogglingly 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 supernovae.
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-thermal 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, Mierkat 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 Mirkat already awarded
by the Royal Astronomical Society for its spectacular observations in radio astronomy, was built
with longer-term goals in mind, namely to be incorporated into the square kilometre array,
With a total collecting area of one square kilometer, 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.
Zarder 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 Fermi bubbles are connected.
There's an elegance in order rising out of chaos, and observing non-thermal 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 Astrum 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.
is a pulling force, or technically it is the curvature of space-time 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 supermassive 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 that we have galaxy clusters.
over extremely large timescales, 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 Magellanic cloud-sized diffuse galaxy called Antlea 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
the Antalier 2 galaxy hidden behind our galactic disk.
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
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 light 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,
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 Antlier 2, the region
where the greater tractor is located is hidden behind our galaxy's disk.
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-attractors
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 greater tractor, there is something even more massive behind it, located 650 million
light years away, called the Shapley Attractor or the Shapley Supercluster.
Located there are many thousands of galaxies densely packed together, with a
mass of 10,000 trillion suns, and everything within 1 billion light years is being pulled towards
it.
On the other hand, looking the opposite direction from the Shapley supercluster, we see an underdense
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 Patreon.
This video had no sponsors, but 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 Astrum 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 matters, making the complexity of space available to everyone.
If you enjoy what we do, come join the Astrum community.
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