Astrum Space - We Thought It Was Impossible, But We’ve Finally Seen It

Episode Date: August 31, 2026

In this compilation, we’re revealing the invisible. These cosmic phenomena were previously unseen, but new technology has finally made it possible. We finally pierced through our dense galactic core, discovered the icy shield surrounding our solar system, and even revealed the skeleton holding the entire Universe together. ▀▀▀▀▀▀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

The universe is full of secrets, and some of the most incredible ones are hiding just beyond the reach of visible light. What if I told you that more than 1.5 billion unseen objects, from galaxies and newborn stars, to some of the oldest stars in our entire galaxy, are sitting just out of reach of us, cloaked in cosmic dust? That's a little frustrating to think about, isn't it? Until now, that is, because thanks to the European Southern Observatory's visible and infrared survey telescope for astronomy, better known as Vista, we can finally lift the veil on these hidden wonders. For the first time in human history, we have a pretty comprehensive infrared map of the Milky Way,

one that pierces through the obscuring fog of space to reveal an unprecedented view of our galaxy and what lies beyond. I'm Alex McCulligan and you're watching Astrum. Join me today as we appreciate how this first of its kind map was made and take a look at some stunning images that reveal previously unknown stars across our galaxy. In September 20204, Vista published the largest and most detailed infrared survey of the Milky Way ever undertaken. Encompassing a 13-year period from 2010 to 2023 across 140 nights of observation, this project has captured around 200,000 images and generated 500 terabytes of data.

That's the same amount of data as it would take to stream a 4K video for nearly three years straight. Vista is part of ESO's Paranel Observatory located in Chile, with its main focus being to map large areas of the sky. Using Vista's infrared camera, known as Vercam, the team was able to peer through the dust and gas that permeates our galaxy and uncover some of the Milky Way's most hidden places. Traditional telescopes allow us to view space in visible wavelengths, which range between between about 380 to 700 nanometers. But Vista isn't like traditional telescopes. Instead of relying on visible light alone, Vista operates at infrared wavelengths between 900 and 1,200

nanometers, allowing it to detect otherwise invisible objects like stars obscured by dust, and cold brown dwarfs, also known as failed stars, which don't emit enough visible light to be seen with a traditional telescope. To get an idea of the difference between visible and infrared light, take a look at these two images of the Lobster Nebula, or NGC 6357, one taken in visible light and the other with Vista's telescope. We can see that in the infrared, the dust that obscures our field of view seems to disappear, revealing what look like hundreds of thousands, or maybe even.

even millions of previously invisible stars. The map was created through Vista variables in the Via Latvia, or VVVVVS survey. Via Latvia being the Latin name for the Milky Way, and its companion project, the VVVVVE extended survey, or VVVVX. The data collected from these two companion projects that make up the Vista Infrared Survey have already led to the publication of more than 300 scientific articles. Unlike other recent space maps, this is one of the most detailed ones ever made. It's the first infrared survey to cover nearly 80% of the Milky Way's luminous mass, and

provides the largest infrared catalog ever made of our galaxy's central region. It allows astronomers to study our galaxy in finer detail than ever before. This survey gives us an accurate 3D view of the inner regions of the Milky Way, which were previously hidden by dust. It covers an area of the sky equivalent to 8,600 full moons, and contains about 10 times more objects than any previously published infrared map from 2012. Our Milky Way consists of a central bulge, a dense, bright, puffed-up collection of stars, the flat disk of two spiral arms wrapping from the ends.

This image shows the area of our galaxy that was mapped in the survey. The red squares marked the central regions of the galaxy, which were observed by the original survey, and then re-observed again by the extended survey. And the other square colours show areas that were only observed as part of the extended survey. From this image, you can see that these surveys have focused right on the central plane of our galaxy, spanning part of the disk and most of the nuclear bulge. But what has Vista revealed? Argentinian astrophysicist Dante Minetti, who led the survey project said,

we've made so many discoveries, we have changed the view of our galaxy forever. And as much as I'd love to talk about all of them in this video, it's probably best I stick to some of the highlights. As part of the survey in 2015, Vista turned its attention to the star formation region of Messier 20, also known as the Trifid Nebula, which lies about 9,000 light years from Earth. Viewed invisible light in this image, we can see a beautiful nebula, glowing pink from the emission of ionized hydrogen, and surrounded by a blue haze of scattered light from young hot stars. The cloud of gas and dust is obscured.

the star-filled space behind it. Now look at this second image taken by Vista's infrared camera. Peering beyond the clouds reveals a whole swarm of new stars. This image not only allows us to see through the Trifid Nebula, but by chance it revealed objects on the far side of our galaxy that had never been seen before. To their surprise, astronomers identified two faint, reddened objects as sea-feed variable stars. While they appear in the image to be just behind the edge of the Trifid Nebula, in reality they are very distant, about seven times farther than the nebula that once helped to block them from our view. Seafid variables are a type of bright star that is unstable.

They brighten and fade over a period of a few days, or a few months, depending on their brightness. The first variable star we ever identified in modern times was Omricon SETI, also known as Mirror. It had been described as a Nova until 1638 when Johannes Hallwoods observed it getting brighter and dimmer in a cycle that lasted 11 months. As for this pair of newly discovered stars, they are the only sea feed variables that we have identified so far in this location, which lies beyond the central bulge on the far side of our galaxy. And they can be really useful too.

You can think of them as a kind of cosmic yardstick that can be used up to distances of tens of millions of light years. If you know how long the star's pulsation period from bright to dim is, then you can infer its absolute brightness as well as its. age. You can compare absolute brightness to the apparent brightness, that is, the amount of light that reaches Earth, so you have a measure of how distant the star is. With a few reference points like these, we can build up a real picture of the scale of our

galaxy and beyond. Looking toward the Galactic Center, a team of astronomers and data scientists found even more candidate Seafeed stars, 655. 5, in fact. They then sorted these into one of two classes, and found that 35 of these 655 stars were classical sea-feeds, the younger of the two. This was really exciting, especially since the Galactic Bulge was thought to contain mostly elderly stars that are at least 8 billion years old.

Recording their pulsation periods, the team revealed that all 35 of these sea-feeds were less than 100 million years old, and some of them may be as young as 25 million years old. To put that in context, our own son is about 4.5 billion years old, so the youngest seafeed has only been around for 0.6% of our son's lifespan. The team's exploration of seafeeds culminated in another major discovery. By mapping the 35 classical seafeeds they found, the team was able to trace a completely new feature in the Milky Way, a thin disk of young stars that stretches right across the galactic bulge. Buried behind thick clouds, it had remained unknown in all previous surveys of the region.

In revealing this structure, combined with the discovery of older sea feeds as I mentioned earlier, scientists have inferred that there has been continuous star formation along the midplane of the galaxy for the past 100 million years. There might also be even younger sea feeds that we haven't seen yet, as these stars would be so bright that they would be saturated in the VVV survey. The fact that we found this thin disk of young stars within the galactic bulge is incredible. We used to think that the galactic bulge was an ancient feature of our galaxy's past, where exclusively old stars had formed separately from the stellar disk, but this finding reveals that things

aren't so black and white, and that the formation of newer stars within the bulge could be a natural progression of our galaxy's evolution. But even more inspiring perhaps is a discovery by the Vista Infrared Survey that lies at the ancient heart of our Milky Way galaxy. In 2016, for the first time, a type of ancient star known as A.R. Lairay, another variable star, was discovered in the center of the Milky Way galaxy by a team led by astrophysicist Dante Manitti and Rodrigo Andreas Ramos. This type of star is usually found in globular clusters, which tend to orbit the outer regions

of the galaxy. A globular cluster is a tightly packed group of stars that contains tens of thousands to millions of stars bound together by gravity. They're also really ancient, containing a stellar population that can be over 10 billion years old. The team found 12 RR Lairay stars during the VV survey, which suggests that they might be the remnants of an ancient globular cluster right at the heart of our galaxy. This finding also provides evidence that might help astronomers to decide between the two

competing theories of how nuclear bulges form. While some scientists think that the nuclear bulge forms early in the galaxy's evolution, when multiple smaller galaxies violently collide, others say that it forms gradually over time, where gas is funneled inwards to trigger star formation. Finding these ancient stars here suggest that the bulging center of the Milky likely grew through the merging of primordial globular clusters, therefore supporting the first theory. So not only does it hint at our own galaxy's beginnings, but it also offers compelling evidence

into how these galactic bulges might form in other similar galaxies. Speaking of ancient stars, Vista was able to find two new globular clusters as part of the infrared survey in 2011. In this visible light image, a known globular cluster, U.K.S. 1, can be seen on the right as a hazy red splotch. This cluster had been the dimest known globular cluster until the new discoveries. Now, compare this same patch of sky, but this time in vistas infrared light. Suddenly we can see what we have been missing.

much more faint than the known U-KS-1, we can make out a second globular cluster, this time in the upper left of the image, which has been named VV-V-Cl-001. Another globular cluster, aptly named VV-CL-002, was found soon after, and this small, faint group of stars may be the closest known globular cluster to the center of the Milky Way. Did you know that there were only 158 known globular clusters in the Milky Way before these new ones were found by Vista? For the survey to identify two more of these rare stellar objects is quite a significant accomplishment.

Within this central region of the galaxy, it's easy for younger stars and cosmic dust to obscure globular clusters, especially since their age prevents them from shining as brightly. But now that they've been revealed, the world. These features bring exciting possibilities for further study. It could just be an illusion of perspective, but scientists have wondered whether VVV CL001 is gravitationally bound to U.K.S.1. If this is the case, then they would be the Milky Way's first known binary globular cluster pair.

We found binary clusters in other galaxies, like in Centaurus A and the Large Magellanic Cloud, But scientists think it might be when these gravitationally bound clusters collide that we get the most massive globular clusters, like Omega Centauri. So studying a binary cluster right in our own galaxy could produce some amazing insights into this process. It's all speculation at the moment, but it's definitely cool to think about. In addition to globular clusters, the Vista infrared survey identified a multitude of of other types of star clusters. At least 96 new open or galactic clusters have been found,

which typically contain fewer, younger stars and are much more common than the globular type. Like the globular clusters, they have been hidden by cosmic dust, but Vista's 4.1 meter infrared telescope has lifted the curtain to show them in all their glory. Take a look at just a few of these stunning images. now have of these objects. One of these open clusters, VVVCL003, is much more difficult to make out in images compared to the tightly packed globular clusters. Try and see the density differences in the stars in this section of the image compared

to the surrounding regions. It was found by Vista 15,000 light years beyond the Milky Way center and also happens to be the first of its kind to be discovered on the far side of the galaxy. The sheer scale of this survey is staggering. Covering a vast region of the sky and mapping more than 1.5 billion objects, this data has already led to fascinating discoveries that are rewriting our understanding of the Milky Way and beyond. And that's just the tip of the iceberg. This survey will serve as a foundation for future telescopes and observations, which will hopefully

be able to expand on Vista's legacy with even higher resolution and sensitivity. We now have the most detailed 3D map that has ever been made of the Milky Way structure and objects, one that unveiled hidden wonders previously beyond our reach, and scientists are already uncovering new galactic features and reshaping our understanding of the galaxy. With the information from this groundbreaking infrared survey, as well as the recent work from Issa's Gaia mission in visible light, it's an exciting time to be an astronomer, and we can expect a flurry of new insights about our own galaxy and the universe as a whole. Vista's infrared observations have unveiled dozens of hidden star clusters and millions of previously

unseen stars. They have revealed new stellar nurseries where stars are born, and they have broadened our understanding of the formation of our Milky Way. Looking at the sky through different wavelengths has brought about a new era of galactic exploration and I can't wait to see what else astronomers and data scientists are going to uncover thanks to Vista's 3D map. What if I told you that there is a colossal structure that begins at the edge of our solar system? One that encircles our sun and all of the planets. But we've never seen it. A shell made up of billions or even trillions of ancient, icy chunks, the size of mountains,

marks the outermost boundary of our solar system, or so we think. Jaw-droppingly far away, beyond the reach of even our most powerful telescopes, the ore cloud is a region shrouded in mystery and speculation, where the sun's influence grows faint as it brushes up against the void of interstellar space. What exactly is this aught cloud? If we've never directly observed it, how do we know it's out there? And why do some people question its existence? Let's find out.

I'm Alex McColgan and you're watching Astrum. Join me today as we venture to the farthest reaches of our solar system and beyond to construct an image of this unseen astronomical wonder. You've probably heard of the asteroid belt, and maybe even the Kuiper belt. At two different locations in our solar system, these roughly donut-shaped bands of debris each move in the same direction, and more or less on the same orbital plane as the planets around our sun. The asteroid belt is the closest to the sun of these two debris rings, located between

Mars and Jupiter, and consists of millions of orbiting asteroids. The Kuiper Belt, on the other hand, was first proposed by astronomer Girard Kuiper as the origin of short-period comets in the mid-20th century. It is a massive field of icy debris out past Neptune. Occasionally, a piece of Kuiper belt debris will get pushed by gravity, sending it on a new orbit closer to the Sun. In some cases, this creates a new short-period comet. These comets have orbits of less than 200 years and are often predictable as they continue

to make subsequent orbits around the Sun. At the same time that Kuiper was investigating short period comets, a Dutch astronomer named Jan Ort was contemplating the origin of long period comets. Few scientists of the 20th century made more contributions to astronomy than Oort. In 1927, he calculated our place in the Milky Way galaxy, and in 1936, and in 1930s, he calculated our place in the Milky Way galaxy. And in 1932, he was the first to find evidence of dark matter, to name a few examples of his discoveries. In 1950, Oort was the first to theorize the existence of a thick bubble of swarming, icy debris

that surrounded our entire solar system, now known as the Oort Cloud. But unlike the asteroid belt and Kuiper belt, it's still yet to be directly observed. To understand this theory, let me explain what led ought to this proposition. Unlike comets with short orbits, such as Halley's comet with an average period of 75.3 years, or comet Enka, with a period of just 3.3 years, long period comets were unpredictable. For one thing, their orbital periods were so long that in some cases they could take as many as 30-mills million years to complete one orbit. And curiously, these comets came from all different directions and had various orbital

inclinations. It was a mystery on the grandest of scales, but Oort noticed a few things that all of these long-period comets had in common. Their orbits indicated that these comets weren't coming from far out in interstellar space, that their origin had to be closer to home. However, as I'll explain in a moment, not too close to home. So if these long-period comets weren't coming from the Kuiper belt and weren't coming from far out in interstellar space, where were they coming from? Ord found a peculiar similarity among the orbits of these comets, one that might provide

the answer to that question. The point in a comet's orbit where it is most distant from the sun is called the Apheelian. Oort noticed that all observed long period comets seem to have an Apheelian that all grouped around a certain distance, around 7.5 trillion kilometers from the sun. That's right, trillion with a T. As you can see, when it comes to the distances I'll be talking about in this video, our typical units of measurement fall a bit short. So instead of using kilometres, I will switch to astronomical units.

One astronomical unit, or AU, is defined as the distance between Earth and the Sun, or about 150 million kilometres. So Earth is one AUU from the Sun. The abhealier grouping that ought noticed, where the long period comets reached their farthest orbital distance from the Sun, was about 50,000 astronomical units. To help picture the orbits of these long-period comets, keep in mind that the outermost planet in our solar system, Neptune, is around 30 AU from the Sun, or about 4.5 billion kilometers. The main region of the Kuiper Belt extends from Neptune's orbit at 30 AU out to around 50 AU, but recent evidence from NASA's new horizon spacecraft suggests a second region of the Kuiper Belt called the Scattered Disc, which continues to a

around 1,000 AU. It's with these key findings from observed comets that they didn't come from far out in interstellar space, orbital distances clustered around 50,000 AU, and the fact that they arrived from any direction and orbital inclination, that Aught theorized a special spherical swarm of icy debris that he believed to be the origin of long period comets. In the years since then, mathematical models have shown agreement with the Ord Cloud theory, and astronomers have further theorized various mechanics by which the Ord Cloud came to be in this current state. The leading idea is that the Ord Cloud formed from ancient debris, leftovers from when our planet formed 4.6 billion years ago. After the planets formed, the surrounding area was still

rich with these smaller, leftover chunks of material called planetesimals. The gravity from these early planets then scattered the leftover material in every direction. Some material was flung out of the solar system entirely, but a significant portion was sent into seemingly random, eccentric orbits around the Sun. These scattered planetesimals had eccentric enough orbits that they were influenced by gravitational forces outside of our solar system, while still remaining captured in our Sun's orbit. And it's believed that this is how these billions or trillions of icy chunks came to be part of the Oort cloud. Gravitational perturbations

can force Khyber Belt objects out of place, creating short-period comets. We think that similar forces are what send Oort cloud objects into elliptical orbits with the Sun, thereby creating long-period comets. These perturbations could be caused by passing stars or molecular clouds, or tidal forces from the Milky Way itself. In fact, about 70,000 years ago, Schultz's star gained the title of the star that came closest to our solar system, actually grazing the outer region of the Ork Cloud. But luckily for us, it didn't cause any catastrophic disruptions to the Ork Cloud

or our solar system at large. Schultz's star is a low-mass binary system made up of a red dwarf and a brown dwarf companion. So, 10 millennia ago, even at a much closer distance to the Ork Cloud, the gravitational influence of this binary star was significantly weaker than that of our much more massive sun. However, while most objects experienced little to no impact during the low-mass star's brief encounter with the edge of the Ork Cloud, numerical simulations from 2018 concluded that Schultz's star is believed to have nudged at least some objects out of place. creating and influencing the trajectory of some long-period comets.

But the sun has been around for over 4 billion years, and that's a lot of time for other close encounters with stars in the distant past. Could these interactions have prevented the Oort Cloud from forming? Our models suggest no. However, Oort Cloud material may get exchanged with passing stars over eons. You see, other more reasons. Recent numerical simulations have suggested that odd clouds could exist around other stars too. Our Oort cloud may also have both an inner and an outer region, each with its own distinct shape.

Some scientists suggest that the inner region may be more like a disc, similar to the donut shape of the Kuiper belt, while the outer region is suggested to form the spherical shell more widely associated with the Oort cloud. Altogether, the inner edge of this two region or cloud may be 2,000 astronomical units from the sun at its closest, with the far edge stretching all the way out into interstellar space, potentially reaching as far as 100,000 astronomical units from the center of our solar system. This means the aught cloud could extend more than 1.5 light years across.

To put that into perspective, since we're talking about very, very large distances, consider Voyager 2 spacecraft for a moment. As of the publication of this video, Voyager 2 has traveled to a distance of about 139 astronomical units from the Sun since its launch from Earth at 1 AU in August of 1977. That's about 3.3 AU per year, or about 56,000 kilometers per hour. It's the second farthest human-made object in space, just after Voyager 1. In August 2007, Voyager 2 passed beyond the boundary of the Heliosphere, the outermost layer of the Sun's atmosphere.

It extends out beyond the planets, and three times further than the distance to Pluto. Outside of the Heliosphere, the Sun's constant flow of charged particles called the solar wind is finally impeded by the interstellar medium. And in November 2018, Voyager 2 finally crossed the final layer of solar turbulence called the helioseith and continued on into interstellar space. Despite passing beyond the heliosphere and well past the main Kuiper belt, Voyager 2 would still need to travel for another 300 or so years just to reach the innermost edge of the ore cloud.

That's how far away it is. to fly through the Ork Cloud, that could take another 30,000 years. Even when travelling at 56,000 kilometers per hour, it still takes all that time just to travel around one and a half light years. If you've ever wondered why interstellar or intergalactic space travel is difficult, keep in mind that our nearest stellar neighbour is Proxima Centauri at around 4.25 light years away. However, some still question the existence of the ore cloud, mainly because we're unable to directly observe it.

Another argument has been made that long period comets may come from other places such as interstellar space, and in fact, the first observation of an interstellar comet, one that had origins from outside our sun's influence, was made in 2019 by amateur astronomer Gennady Borisov. Professional astronomers joined in to collect data on comments. Comet Borosov, named after its first observer. They found an unusual composition, a higher concentration of carbon monoxide than the average comet originating from our own solar system, suggesting that this comet may have formed in the presence of a red dwarf, a different type of star than our sun.

And yet, the vast majority of astronomers agree that the ore cloud is really out there, despite the fact that we've never laid eyes on it. of indirect observations and mathematical models show great support for the theory, and the evidence continues to add up. But why is it exactly that we've never been able to see the cloud? After all, with telescopes we can see stars far beyond our own solar system, and even the shapes of distant galaxies. The difference is size and light. Think about it. A piece of The orc cloud debris is roughly the size of one mountain on Earth. Let's consider Mount Everest at around 9 km tall.

Now consider the or the ort clouds' innermost boundary begins somewhere around 3,000 AU, or roughly 450 million kilometres from the sun. The distance from the sun to the nearest piece of aught cloud debris is 50 million times the size of the debris. Talk about looking for a needle in a haystack. But more crucially even, is that stars and galaxies give off light, but aught debris does not. The planets are relatively close to the sun, so they are able to reflect the sun's light and therefore are visible. Likewise, the asteroid belt, and even the Kuiper belt, are close enough to the

sun that we can use telescopes to directly observe their debris. But outside of the heliosphere, the old cloud is just too far and too dark for our telescopes to catch a glist. Despite the Orp Cloud's gargantuan footprint and pivotal role in shaping our understanding of the origin of many long-period comets, for now we can still only infer its existence through mathematical models and indirect observation. But don't let our inability to make direct observations discourage you from following the evidence. I can think of a few other times in history when scientists put forth monumental theories

despite a lack of direct observation. For example, in the 16th and 17th centuries, respectively, Copernicus and Galileo put forth the theory that the planets orbited around the Sun, contradicting a widely held belief at the time that the Earth was the center of the solar universe. Their theory of a heliocentric solar system was not based on direct observation, but rather on indirect observation of the orbit of the planets. As we know, that theory turned out to be spot on. That's the thing I love about science and the pursuit of knowledge.

There's always more to learn. The farther we travel through time, the better our understanding of the solar system will get. Who knows? Maybe in 100 years, future astronomers will have found a way to prove the existence of the Ork Cloud once and for all. Or maybe they'll have found a whole new explanation for long period comets. Until then, the all-cloud remains one of astronomy's most compelling enigmas.

I'm sure we've all seen the breathtaking imagery from the Hubble Space Telescope of beautiful and multicolored nebula. It almost seems as if a contemporary artist flicked different colours onto a canvas, but this isn't just a pretty picture. What you are seeing here are actual structures, tens to thousands of light years across. But how are these images so colourful? Does it really appear like that in real life? Ready to take your investing knowledge to pro level?

This is Fidelity Connects, your daily edge in the markets. Get deep insights on real-time market topics that may impact your investment portfolio. Listen to Fidelity Connects on Spotify today and power your next move tomorrow. To answer this question, let's give you some context. Nebula may appear solid or maybe even like clouds, but that is far from reality. Nebula are extremely diffused gas clouds. On average, you may get about 10 to 100 particles per cubic centimetre. This is far less than any artificial vacuum produced on Earth.

To give you a sense of how little that really is, a comparable cubic centimetre at sea level on Earth contains 10 quintillion particles. That's 10 to the power of 19 particles. On the other hand, if you were to have a nebula the size of Earth, it may only have a total mass of a few kilograms. Orion, perhaps the brightest nebula in our sky, is just about bright enough to be seen with the naked eye on a clear night. However, nebula can be a lot brighter too.

If the tarantula nebula found in the large Magellanic cloud was as close to us as the the Orion Nebula is, it would even be visible during the day. But if nebula are so sparse, how can we see them at all? It's important to remember the scales that are at play here. While nebula are sparse, they are also massive. H2 regions, which are a specific type of nebula, are known as stellar nurseries. These massive clouds can collapse and coalesce, and when they do, they form stars. A single nebula can contain enough mass to create hundreds to thousands of stars, and it

is actually these newly formed stars that light up the gas in a nebula. Solar radiation shoots away from stars within a nebula, ionizing the nebula's particles, which releases this energy at a specific light wavelength. This means H2 regions are known as something called emission nebula, because ionized atoms within are emitting their own light. The process happening in an emission nebula is comparable to what happens in a neon light, where electricity ionizes neon within the bulb, causing it to light up. However, in a nebula, it's not neon that lights up.

In fact, in the Hubble images, each color shows a different ionized atom. Unfortunately though, I can't tell you a blanket rule for colors in Hubble images. So, while in this image of the Kurena nebula, reds correspond to sulfur atoms, greens to hydrogen, and blues to oxygen, in this image of the Swan Nebula, blues correspond to visible light blues, greens to oxygen, and reds to infrared and hydrogen. That's because of the way Hubble takes its photos. Hubble is primarily a visible light telescope, but its optical range does also extend into the ultraviolet and infrared.

When scientists look at a nebula, they often want to see what it is made of, so we'll photograph the object using specific filters. So say they want to see hydrogen in a nebula. They will image the nebula using a filter that lets light being emitted along 658 nanometer wavelengths through, or in other words, the emission band of hydrogen. After that, they are left with a black and white image. Then they may decide to image the nebula again, this time looking for some. sulfur along 672 nanometer wavelengths, and then again looking for oxygen along 501 nanometer

wavelengths. Scientists then assign colors to each of these different photos, and combine them together to produce the colors you see here. As you browse Hubble images on their website, you can see for yourself what the colors have been assigned to by looking to see what wavelengths of light were used. For Hubble images of nebula, they are pretty much always a false color. However, Hubble does also take natural color images too. The sombrero galaxy, for instance, had three different images taken in blue, red, and green, or RGB. So the colors you see here are how you would see this galaxy, were it bright enough

for you to see it. So, if Hubble's images of nebula are false color, what would they really look like to us? Generally speaking, a lot more red. The European Southern Observatory also looks at a lot of the same objects Hubble does, although often using different color filters. Going back to the Kurena Nebula, on ESO's website, we see that the color bands are RGB or natural light, so we know that what we are seeing here is the Krena Nebula as we would see it.

Here's ESO's version of Orion, except this time with ultraviolet and hydrogen overlaid on top of natural colors. So far, we've only discussed the most famous nebula type, H2 regions, or emission nebula. However, it is worth mentioning that there are a few other types of nebula too. You also have reflection nebula, where the energy from stars isn't enough to ionize the nebula. Instead, it reflects or scatters the starlight, meaning these nebula tend to have similar frequency spectrums to nearby stars, often appearing slightly blue.

You also have dark nebula, or nebula with no stars around them to illuminate them. These almost appear pitch black. All in all, nebula are not as colourful as you may have initially thought, but to me that doesn't make them any less interesting. Looking through these filters means we can understand a lot more about nebula than we otherwise could have, and they do make for beautiful images. Despite existing on a small planet in the tiny corner of the cosmos, astronomers know exactly how much visible matter the entire universe should contain.

The problem is that for decades, 40% of it has been missing. And I'm not just talking about the ever mysterious dark matter and dark energy. Galaxy clusters don't seem to have as much visible mass as our model's sales. They should be there. Entire galaxies seem to have lost huge reservoirs of the material they were born with. Even the space between galaxies, enormous cosmic deserts, are emptier than our best theories predict. This missing mass has to be out there.

That, or all our models of cosmology, are wrong. But every time we've looked, we've found nothing. Believe me, we've tried. We've used our most powerful telescopes, deepest surveys, and most sensitive detectors in the search. The missing mass just remains invisible, slipping past our instruments like a ghost. That is, until now. For the first time in history, we may have finally found where the missing mass of all the universe

has been hiding. It's in plain sight. Astronomers have captured images of vast, gaseous filaments that stretch 23 million light years between galaxy clusters. It may just be one filament, but finding it has huge ramifications. Is this the very first detailed image of the cosmic web? As scientists now hunt for more, this discovery has the power to determine whether our cosmological models are correct.

I'm Alex McColgan and you're watching Astrum. Join me as we reveal how astronomers have snatched a glimpse of the near invisible network that underpins the cosmos, finally revealing the hiding place for our universe's missing visible matter. And with it, let's start unraveling the truth behind our cosmic evolution. When we measure all of the gas, dust, planets, stars and galaxies, everything we can see in the whole universe, using everything from infrared to visible light and beyond to gamma rays, it adds up to a colossal amount, more than 100 sextillion kilograms.

That's 10 with 53 zeros after it. But really, this only accounts for a small fraction of the total matter that scientists predict to exist. In fact, this visible ordinary matter is thought to make up just 5% of the universe. The rest is stuff we don't completely understand. Dark matter is believed to account for 27%, and dark energy 68%. Despite their names, dark energy isn't related to dark matter. What they have in common is that we can't detect or see them.

Dark energy is thought to be a seemingly invisible type of energy, causing the universe's expansion to accelerate over time, and dark matter is a type of matter that has mass, but is invisible to us, as it doesn't absorb, reflect, or emit any light. I've talked about dark energy in previous videos, and that is truly its own mystery. You can explore those if you're interested to find out more about the topic. But for this video, I'll just focus on the matter at hand. So 95% of our universe is likely not made of visible ordinary matter, and of the 5% that is technically visible matter, also known as barionic matter, about 40% has been missing since

the Big Bang 13.8 billion years ago. Now, I know what you're thinking. How do we know it's missing if we've never seen it? We certainly weren't around back then. Thankfully, the early universe itself left us the answer. Measurements of the cosmic microwave background have allowed cosmologists to calculate exactly how much barionic and non-barionic matter was created as a result of the Big Bang, to an accuracy level of better than a few percent.

That gives us a precise budget for how many atoms should be in the universe today. But just because it's made of stuff that's visible to us doesn't mean it's easy to see. When astronomers go out and count up all the stars, gas, dust and plasma we can see, with the help of models and simulations, we only find about 60% of what should be there. The rest has to exist for early universe physics to make sense, but unless we can find it, we can't prove that our models are right. Maybe we've got it all wrong. Thankfully, scientists haven't been that quick to give up, and instead turn their attention

to working out where the missing mass may be lurking. And they came up with an intriguing hypothesis. Missing barionic matter is not the only missing mass, and perhaps they're hiding together. Nearly a century ago, Swiss-born astronomer Fritz Zviki noticed that galaxies in the coma cluster moved too quickly for the amount of gravity that would be created by their visible matter alone. Yes, including the missing stuff. Instead, he thought another form of mass must be there, and in 1933, Zviki dubbed this missing substance Dunkel Materi, the German for dark matter.

In the 1970s, American astronomer Vera Rubin had a similar experience. She was observing spiral galaxies and wondered how stars on the outer edge of the spiral galaxies were able to move so quickly without flying off into space. Again, some unknown mass must have been pulling them back in, and she concluded the same as Zviki. There must be dark matter holding them together. This new type of stuff interacts with its ordinary barionic counterpart through gravity, but it doesn't interact with the electromagnetic spectrum, meaning that it doesn't absorb, reflect, or emit any light. This makes dark matter extremely difficult to find, and seemingly impossible to observe,

at least directly. Yet it influences the cosmos on a galactic scale. It may even be helping to conceal our missing barionic matter. the 1980s, early observations of galaxy distribution have revealed a cosmic pattern, a web, like a backbone across the universe. This skeleton-like structure has become known as the cosmic web. It's thought to have formed as a result of slight density fluctuations in the early universe, which can be seen in the cosmic microwave background, or CMB, a fingerprint of our universe's ancient microwave radiation from about 380,000 years after the Big Bang.

These tiny fluctuations in density laid out a blueprint for where matter would collect over space and time. Where there were higher densities, more mass would be drawn in, until this great structure was formed. We already know that CNB simulations using supercomputers estimate that dark matter accounts for five times more of the universe than ordinary matter, So it's perhaps no surprise that the cosmic web is thought to contain primarily dark matter. Permeating every corner of our universe, it's made of filaments stretching tens to hundreds of millions of lighters across the universe. Where filaments intersect, the concentration of mass is so great that high density nodes

are able to form, containing hundreds or even thousands of galaxies. The cosmic web is real. We've mapped large swaths of it. Our galaxy is part of what's known as the local group, a collection of a few dozen neighboring galaxies near to our own. Our local group belongs to a larger collection called the Laniercea supercluster, which contains some 100,000 galaxies and measures 500 million lighters across. As you might have guessed, all these galaxies are strong along the cosmic web.

like beads on strings, perched along the edge of great voids. But even though we've been mapping this cosmic web for decades, most of what we can see is the beads. The distribution of galaxy clusters along the web, not the strings that hold them together or the filaments themselves. Or is it? Whilst most of the visible matter in the universe is tied up in galaxies, not all of it is. The dark matter in the cosmic web has a pretty strong pole itself. There, bound up as vast, diffuse gas in those long strings or filaments, is where large-scale cosmological simulations have predicted we might not only find dark matter,

but our missing invisible matter too. This low-density, diffuse gas is known as the warm, hot, intergalactic medium. But simulations, are one thing. Detecting these diffuse filaments is another. And this is where historically, we've not had much luck, although that started to change about 20 years ago. In 2005, NASA's Chandra X-ray Observatory imaged two huge intergalactic clouds of diffuse gas. We'd seen clouds like this around our own galaxy and in others local to us, but not between distant galaxies. Could it be gas on the cosmic web? This was some of the first evidence that the cosmic web was hiding our missing mass, but the light was too faint to completely isolate it,

so scientists couldn't quite be sure. Then, in 2012, a combination of 18 Hubble images was used to infer the presence of a filament funneling matter into the galaxy cluster, Max J0717. Scientists found it by studying the distortion of light from background galaxies due to the gravity of the filament's dark matter. But again, it wasn't a direct detection. We still couldn't say we've actually seen them. Inching ever closer to a discovery, it was just two years later that astronomers moved beyond indirect detection and statistical evidence into the realm of the visible.

A team led by Sebastiano Cantalupo from the University of California observed an enormous filament of hydrogen gas. At nearly 2 million light years across, they spotted it after it was illuminated by a giant cosmic flashlight, a bright quasar shining at it from 10 billion light years away. This was the first time part of the cosmic web had been seen directly. Using the same illumination principle, in 2019, astronomers revealed whole networks of hydrogen filaments surrounding a massive proto-cluster, directly imaging the web on megaparsec scales. But these detections were only possible thanks to our cosmic flashlights.

To understand cosmic filaments as they typically exist, in darkness, we needed a new imaging technique. And in 2023, scientists made a breakthrough. At the WM. Kek Observatory in Hawaii, a team of astronomers had designed a dedicated instrument to search for filaments of hydrogen. More specifically, dim Lyman Alpha emission, the spectral fingerprint of hydrogen as it absorbs and reemits radiation. And it worked. In fact, they've made entire 3D maps of these filaments. This was just the start of the discoveries. In January 2025, the picture sharpened dramatically. A team of international astronomers captured one of the clearest direct images yet.

Using the multi-unit spectroscopic explorer, or muse, mounted on the very large telescope at the European Southern Observatory, they imaged a pair of quasar host galaxies with a cosmic filament about 3 million light years long. And using supercomputer models built on the muse data, researchers were able to simulate a filament that matches the one they observed in real life. This was a spectacular achievement. But there was a catch. These observations were from the early universe.

They traced cooler hydrogen gas, billions of years in the past, not hot, diffuse material thought to contain most of the universe's missing baryonic matter today. Our models predict it stretched along thin filaments of the cosmic web in the local universe, but here the signal is far fainter and harder to isolate. We were stuck. In June 2025, astronomers finally found what they were looking for. They were able to isolate and spectroscopically measure the hot, low-density gas of an individual cosmic web filament in the local.

universe, marking a breakthrough moment in our quest to locate the missing baryonic matter. A team of European researchers headed by lead author Konstantinos Migas at Leiden University in the Netherlands used Jax's Suzaku X-ray Space Telescope to map a single filament in faint X-ray emissions over a wide area of space. They then use the X-MM Newton to pinpoint sources of X-ray contamination, in this case supermassive black holes, which had to be removed from the data in order to map the filament. In this image, you can see what they found. A filament of the cosmic web connecting four galaxy clusters to on each end, each one

as a white spot surrounded by colour. The band of purple stretched between them, resembling a honeycomb or bone marrow-like texture, is the filament of X-ray emitting hot gas. Located in the Shapley Supercluster, a supercluster of more than 8,000 galaxies, the filament stretches across a distance of 23 million light years, which is the equivalent of about 230 Milky Way's end-to-end. Its mass comes in at roughly 10 times that of the entire Milky Way galaxy, and the temperature of the filament's hot gas is a score watching 10 million degrees Celsius. It reveals in detail for the first time how galaxy clusters are connected over colossal distances

and uncover the vast cosmic web that underpins the structure of our entire universe, like the very bones of a cosmic skeleton upon which everything else forms. And according to the paper's co-author, the filament is exactly what we expected from the best large-scale cosmological simulations of the universe. We got it right. The latest breakthroughs in observing filaments lend important evidence and support for our current standard model of cosmic evolution, known as the Lambda called Dark Matter model.

The model is underpinned by dark matter, which has been too complicated for us to catch a glimpse of thus far. So observing this, once thought missing visible matter, on the cosmic web is a big step in the right direction. But to truly know whether our models match reality, we need more than one or two filaments. We need to map the entire skeleton, or at least much more of it. And that is where another mission, Euclid, comes in. Launched in 2023, he says Euclid mission is designed to piece together a more accurate picture

of the cosmic web structure and history and dig into the world. nature of dark matter and dark energy. Euclid will help us measure galactic shapes with precision, revealing how dark matter distorts space through gravitational lensing and measure red shifts, giving us a 3D position for each galaxy. This combination will allow Euclid to infer their locations of the dark matter filaments, not just the galaxies on them, and give us precise locations to look for more gas. By 2030, Euclid will like to light likely be able to confirm if the Cosmic Web matches results from the XMM Newton filament discovery and the pattern seen in the cosmic microwave background.

If it's a perfect match, that would be one of the strongest confirmations of the Big Bang model in the history of science. If not, then something is fundamentally missing in our standard model, whether it's our understanding of dark matter, gravity, or the early use. universe. Either way, with the help of Euclid and the latest observations of these cosmic filaments, cosmology is poised to be changed forever. A massive thank you to our astronomers 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.

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