Astrum Space - These Orbits Are Not Normal

Episode Date: June 15, 2026

This compilation explores the weirdest orbits that could ever exist. We’ll explore backwards-orbiting Moons, strange orbits at the outer edge of our Solar System, and theorise how planets could exist with multiple suns. Join us to find out how these weird orbits actually work, and why some don’t behave how you’d expect. ▀▀▀▀▀▀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

This episode is brought to you by Activia. You might already be eating yogurt, but not all yogurts are created equal. Activia contains over one billion probiotics per serving to survive and reach the gut alive. When it comes to gut health, Activia is the number one family doctor-recommended probiotic yogurt brand. Choose Activia. Feel good from the inside out. Visitactivia.ca for more details. In our solar system, we like to keep things simple. the one star found in the centre, with everything else orbiting around it, as is the case

for most planetary systems found in the universe. However, there are some planetary systems out there where things get a bit more complicated, specifically multi-star systems, where there are two or more stars that orbit each other. In such configurations, what happens to any planets orbiting them? In fact, can planets orbit them at all with the gravitational tugs from different directions? To answer the latter question, the simple answer is yes. Planets can orbit in such situations, although to answer the former question, there is no one answer fits all rule about how a planetary system in a multistar system might look.

What we can do, however, is explore some of the possibilities out there. But before we look at planets, it would be good to understand. how multistar systems work. For the most part, stable star systems have organized themselves into hierarchical systems. This is due to the proximity in which they formed with each other, which we will touch on a little later. Binary star systems are generally simple enough. Binary stars orbit around a barric center, or in other words, their center of mass.

If the masses of these two stars are similar, then nearly symmetrical elliptical orbits are often seen. Although, there can be occasions where they orbit in circles in a similar fashion to Pluto and Sharon. In the case that one object is more massive than the other, then the more massive objects orbit doesn't take it as far out compared to the less massive object. Beyond binary systems, you can have 3, 4, 5, 6, 7, or more stars in the same system, And as you will see, there is a structure within these systems to keep them stable.

In the case of three stars, you'll have two stars orbiting each other in a binary configuration, with the third orbiting around a barric centre with the other two. This keeps the system stable, because if three stars had their orbits cross, one would certainly get ejected from the system at some point. In a three star system, two of the stars are contained in their own enclosed little system, acting as one star in the grand scheme of the whole system itself. We group this binary configuration into a tier, with that tier acting together in its association with the single star.

In a way, once you have grouped the binary configuration in the system, this upper tier now acts like a two star system again, with the two stars and the one star orbiting each other. In the case of four stars, you'll either have two binary configurations orbiting around a barrisome, center, or one binary system orbiting a barricent with a third star, and all three of those stars orbiting around a barric center with a fourth star. From here on is where the hierarchical system really comes in handy. With a chart like this, you can easily see how the system works. In the two-binary configuration case, you have the two binaries orbiting the system's center

of mass. In the single binary and two single stars configuration, you'll add another lower tier in the configuration. You have the binary here, which orbits this third star, and all three of these stars are orbiting together with the fourth star. If there are more stars in the system, say five, you can have an array of configurations with various binaries or single stars on a variety of tiers. Yet with this chart you can easily see where the mass lies.

You can do the same for systems with 6, 7 or more stars, but anything above 7 is exceptionally rare, and probably won't remain stable, although maybe there are examples somewhere in the universe where it exists. So let's add planets into the mix. Could there be a planet out there with 7 suns in their sky? Well, yes. Let's have a look at this hypothetical 7 star system again. By here, there are three stars in a configuration, two in a binary configuration and a single star.

We see that the single star has planets that specifically only orbit that star. They have one sun. Beyond that, there are planets that orbit both that star and its binary companions. These planets could be said to have three suns as they are orbiting three stars. Going to the top tier, there is a planet here that orbits the other. the entire system. This planet could be said to have seven suns. Let's see what that looks like outside this graph.

Interestingly, in a seven star system, from this distance it only looks like the orbit of a binary. That's because each set of stars is found in one of these two points. Here is the planet with seven suns. Its orbit takes it so far out that these stars aren't very bright in the sky, so even though Though it has seven suns, they don't really provide much in the way of warmth or light. Zooming in on the set containing three stars, we see the planets which orbit all three of these stars.

These stars would appear much larger in this planet sky compared to the planet sky that was orbiting all seven. In this example, the two in the binary configuration appear almost too close together to distinguish, with a single star clearly separate. The other four stars that are part of the other set in the system are dim in the sky, they are very far away, and again don't provide much in the way of light or warmth, meaning there is a clear day and night on these planets. Interestingly though, this other set of stars would get marginally brighter and dimmer during

their orbits, and the distance between their systems orbits would get more noticeable as they get closer. Lastly, let's look at a planet orbiting just the one star in this system. It orbits closely to the star and is tidily locked, although the night side would be disrupted by the binary configuration this star orbits with, as the planet's orbit can take it between the single star and the binary stars. The binaries orbit together closely, and so wouldn't easily be distinguished in the sky without a filter.

Then, the other set of stars in the system, would be dim and appear far away. This may make you wonder how many systems out there have more than one star. Are we unusual? Or is it the trend that there is only one star per system? Well, if you look up into a clear night sky, it may surprise you to know that most of these stars are binaries. The brightest star in the sky, Sirius, is a binary. The centauri, the closest star to us, is a binary, or maybe even a trinery if you include proxima.

Polaris, the North Star, is also a binary. So for the longest time, astronomers thought that we were the unusual ones. However, it's coming to light with the improvements in technology that this is not the case, and that most star systems only contain one star. Perhaps the reason why the brightest stars in our sky are binaries is because, you know, they are giving off twice the light. Single stars are just generally dimmer and harder to see in comparison. It doesn't help either that 85% of all stars in existence are red dwarfs, and it seems that only about 25% of them have companions. In fact, it's interesting

that binaries occur much more frequently with the really massive stars, the blue and white giants. This could be because of how these stars formed. Red dwarfs weren't pumped with as much material as they were forming, hence why they never attained the mass of a blue giant. In an environment where forming a blue giant is possible, however, models suggest that several stars could form at the same time. At first these systems would be chaotic, the stars would be ejected until order could be found. The ones that remained and survived were the ones that ended up absorbing the most interstellar

medium, thus becoming the most massive of stars. The interstellar medium that ended up caught in protoplanetary disks around these stars later form planets. In such turbulent conditions, it is likely that it's harder for planets to form compared to around a single star, however, it's certainly not impossible. So perhaps there is indeed somewhere out there where there is a planet with seven suns. What a cool sight that would be too. I just can't help letting my imagination run with what that would be like.

However, it probably wouldn't be so great for a nice, consistent day and night cycle. So there we have it. How planets orbit in multi-star systems. Saturn is easily the most recognizable planet in our solar system. And some of its moons are the most famous too. Titan, Enceladus and Ria. All move like clockwork and an elegant dance around this ringed giant. And out in the far reaches of Saturn's gravitational influence, millions of kilometers from

the planet, prowls an object that does not belong. It is dark, scarred and solitary. It moves backwards, crashing against the flow of the rest of the system. It is a time capsule from an era when the giant planets migrated and the solar system tore itself apart. This is a world of landslides, of frozen carbon dioxide, and a hidden ring of dust so massive it dwarfs Saturn itself. It is a moon that shouldn't be there, a visitor snatched by Saturn's gravity and held

prisoner for 4 billion years. This is Phoebe. I'm Alex McColgan and you're watching Astrum. Join me today as we journey to the edge. of Saturn's domain, to unravel the secrets of its darkest, most mysterious moon. The story of Phoebe begins with a quiet revolution. For thousands of years, astronomy was limited by what it's possible to see with the human eye. First astronomers used the naked eye, and then, in the early 1600s, the invention of the telescope revolutionized what it was

possible to see. But it wasn't until the 19th century that the dry plate photographic revolution changed everything. For the first time, astronomers could leave a camera shutter open for hours, allowing light to accumulate on glass plates, revealing objects thousands of times fainter than what Galileo or Castini could have ever dreamed of observing themselves. In 1898, a Tijuana from the Harvard College Observatory, led by William Henry Pickering, set up an outpost in the thin, dry air of Arequipa, Peru. Using the 24-inch Bruce Telescope, they began a deep photographic survey of the southern sky. The work was tedious. The glass plates were shipped back to Cambridge, Massachusetts, where they were poured over by computers, human analysts

using magnifying loops to spot new objects on the plates. Then, in 1890, Pickering was examining plates taken the previous August when he found a speck. It was faint, magnitude 15.5, roughly 4,000 times fainter than the limit of the naked eye. But what was most fascinating about this object was that it moved. Pickering traced its path across multiple nights. The stars stayed fixed. Saturn moved, but this spec moved with Saturn, yet not like the other moons we already knew of.

On the 18th of March 1899, he announced the discovery of Phoebe. It was a landmark moment, the first natural satellite in history to be discovered not by direct observation, but by an image on a photographic plate. As astronomers tracked Phoebe in the early 20th century, the excitement of discovery turned into confusion. Phoebe wasn't just far away. It was wrong. The solar system has rules.

Because everything formed from the same spinning disk of gas, the planets in their moons almost universally spin an orbit in the same direction, counterclockwise or program. Phoebe breaks this law. It orbits Saturn clockwise in the opposite direction to the planet's rotation and the other moons. This is known as a retrograde orbit. Now when we find a moon orbiting backwards, we know one thing with absolute certainty. It did not form there.

If Phoebe had formed from the dust surrounding the infant Saturn, the drag from the gas cloud would have forced it into a pro-grade orbit. A retrograde orbit is a smoking gun, pointing to a very violent history. It means Phoebe is an immigrant, a captured object that formed elsewhere and was ensnared by Saturn's gravity. And the distance of this moon is staggering.

Phoebe orbits at a mean distance of nearly 13 million kilometers from Saturn. That is nearly four times, further out the niaputus, and almost a quarter of the distance from the sun to Mercury. It takes 550 days, about 18 months, for Phoebe to complete a single, lonely lap around the ring planet. It's so far out that from the surface of Phoebe, you would not be able to see the rings of Saturn with the naked eye.

All you would see is the glare of a tiny but bright planet in the night sky. Because it is so far from its host planet, Phoebe went uninvestigated for nearly a century. Even Voyager 2, which flew through the system in 1981, only saw it as a jagged, dark blob from 2.2 million kilometers away. We knew it was there. We knew it was weird, but we didn't know what it was. That changed with Cassini. When mission planners were designing the trajectory for the Cassini spacecraft, they realized

they had a unique problem. To enter orbit around Saturn, Cassini had to break. This meant approaching the planet from the outside in. They realized that on this arrival leg, before the critical engine burn that would trap the probe in Saturn's gravity, they could pass by Phoebe. It was a one-shot chance to get a close-up look at the this elusive moon. The encounter had to happen on the 11th of June 2004, 19 days before orbital insertion, because once Cassini fired its engines and settled into the inner system, that was it. It would never have the fuel to go back to Phoebe or match its backward speed. For a few frantic hours, the dark moon filled the cameras, transforming from a dot into a complex world.

The relative velocity of the flyby was a staggering 5.8 kilometers per second, and then Phoebe was gone, receding into the darkness. The images Cassini Beamback revealed a world that looked nothing like its siblings. Phoebe is roughly spherical, about 213 kilometers across, but it looks absolutely beaten. It is dark, with an albedo of just 10%, making it as black as asphalt. Cassini's cameras mapped the surface in detail, revealing the crater saturation and brightness variations. Spectrometers analysed the surface composition, detecting water ice, carbon dioxide, iron-bearing minerals, and signatures consistent with primitive carbonaceous materials found in meteorites expected in outer solar,

and bodies. Dominating the surface is the Jason Crater, a massive impact basin 101 kilometers wide, nearly half the diameter of the moon itself. The fact that Phoebe survived such a hit is not only astonishing, it tells us it is a solid body and not a loose pile of rubble like some asteroids we've been visiting, but the most striking features were the landslides. Gravity on Phoebe is weak, but strong enough that when meteorite strike, they destabilise the crater walls. Cassini saw bright white streaks where the dark surface material had slumped away. Phoebe isn't a rock, it's a dirty ice ball.

It is an ice-rich body coated in a thin veneer of dark dust, perhaps only a few hundred meters thick. The true nature of Phoebe was hidden in its density. By measuring how much the moon tugged on Cassini during the flyby, scientists calculated its density to be about 1.63 grams per centimeter cube. This is the key. Saturn's regular moons are mostly pure, porous ice, about one gram per cubic centimeter. Phoebe is much denser, implying it is around 53 to 66. 7% rock. This density is similar to Pluto and Triton. It suggests that Phoebe is a planetary

embryo, a world that started to differentiate, separating into a rocky core and an icy mantle, but was stopped sometime in its development. The chemical fingerprint confirmed it. Yacini spectrometers detected carbon dioxide trapped in the surface rocks. On the inner moons, volatile CO2 would have boiled away. a year's ago. Its presence here confirms that Phoebe formed in the deep freeze of the outer solar system, far beyond the orbit of Neptune, a survivor from the Kuiper Belt that found its way to Saturn and got caught up in its gravitational pull, and Phoebe's story doesn't end with its capture. For billions of years, this dark moon has been subjected to a relentless

rain of micro-meteroids. Every tiny impact, black, a little bit of that dark surface material into space. Because Phoebe's gravity is so weak, this dust escapes easily, entering a retrograde orbit around Saturn. Over billions of years, this dust has accumulated into a structure that remained hidden from humanity until 2009. Using the Spitzer Space Telescope, astronomers discovered the Phoebe Ring. And it is enormous. This This ring is invisible to the naked eye, but in infrared, it glows. It spans from 6 million to 16 million kilometers from the planet. You could fit roughly 1 billion Earths within its volume, and if you could see it from Earth,

it would be the width of two full moons in our sky. It is the largest ring in the solar system, and Phoebe orbits right in its heart. the dust particles within it are spread extraordinarily thin, making it virtually invisible in reflected sunlight. Spitzer could only detect it by sensing the faint thermal glow emitted by the sparse dust grains themselves. Crucially, this gigantic ring is tilted by 27 degrees relative to Saturn's main flat ring plane, perfectly matching the inclination of Phoebe's own orbit. It also shares Phoebe's retrograde motion. The ring's composition, inferred from its infrared signature,

is consistent with the dark, primitive material making up Phoebe's surface. The source was confirmed. Micrometeoroid impacts on Phoebe are, in fact, generating this vast, diffuse halo of dust. This discovery solved one of the oldest mysteries in astronomy. In 1671, Giovanni Cassini discovered the moon Iappitus and noticed it had a ying-yang appearance. One hemisphere as whiter snow, the other black as coal. Well, now we know. Phoebe orbits retrograde or clockwise, while Iapetus orbits prograde or counterclockwise.

As the dark dust from the Phoebe ring spirals inward towards the planet, it slams head head on into the leading face of Iappitus. Phoebe is effectively spray painting its neighbor from millions of kilometers away, like an interstellar banksie, creating the stark contrast that puzzled astronomers for 300 years. But how did this dark, dusty moon, born far beyond Neptune, end up at Saturn, so much closer to the sun? The leading theory, known as the Nice model suggests that four billion years ago, the giant planets migrated, violently disrupting the primordial Kuiper belt. In that gravitational chaos, countless icy bodies were thrown into the sun or ejected

into interstellar space. But a lucky few like Triton and Phoebe were captured and became moons. Phoebe then is more than just a moon. It's a relic. It is a surviving piece of the building blocks that formed the outer solar system, preserved in deep freeze of Saturn's gravity. It tells us of a time when the planets moved, flinging rocks around the solar system to be captured by the huge gas giants that dominated.

And while we've learned much, questions remain. What lies beneath the dark surface layer? Does it have a differentiated internal structure? a rocky core surrounded by an icy mantle. Can we definitively pinpoint its origin region within the Kiva belt or scattered disk? Phoebe remains an object of intense interest. A primordial messenger holding clues to the materials, processes and dynamics that governed the early solar system.

It's a reminder that planetary systems are not static, but dynamic places where objects can wander, be captured and leave their imprint far. from where they originated. Phoebe, the dark intruder, continues to orbit Saturn, a lonely sentinel that has left a permanent mark on the Saturn system.

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Old Navy's drapey denim wide leg. 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

Ork 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 Oort 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. 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 aught. In 1927, 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 Oort to this proposition.

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 million years to complete one orbit. And, curiously, these comets came from all their day. 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,

but 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? Oort 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. Port noticed that all observed long period comets seem to have an upheelian 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 kilometers, 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 AU from the Sun, the abhealia 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 average planets 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 around 1,000 AU.

with these key findings from observed comets that they didn't come from far out in interstellar space, the 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 Aort cloud theory, and astronomers The performers have further theorized various mechanics by which the Ord Cloud came to be in its 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. The 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 aught 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 Orch 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 Orc 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 recent numerical simulations have suggested that Oort clouds could exist around other stars. stars too. Our Ord 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 Ork Cloud. Altogether, the inner edge of this two-region Ork 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 Oort 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 heliosheath 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 Ork Cloud. That's how far away it is. And to fly through the Ork Cloud, that could take another 30,000 years. Even when traveling 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 neighbor is Proxima Centauri at around

4.25 light years away. However, some still question the existence of the all-cloud, mainly because were 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 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. Plenty of indirect observations and mathematical models show great support for the third theory, and the evidence continues to add up. But why is it exactly that we've never been able to see the old 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 orc cloud debris is roughly the size of one mountain on Earth. Let's consider

Mount Everest at around nine kilometres tall. Now consider the all of the all of the all of 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 Oort Cloud is just too far and too dark for our telescopes to catch a glimpse. Despite the Oort 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 father 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 orc cloud remains one of astronomy's most compelling enigmas.

Why does Pluto and his big moon Sharon orbit around a point in empty space? Is there something invisible and hugely dense there? As the New Horizons probe approached Pluto and Sharon in 2015, it saw this orbiting phenomenon up close and in detail. But in reality, scientists were expecting this before New Horizons even arrived, even though they had never detected anything present at that point. This is because everything in space, not just Pluto, orbit around a barricentor. A barry centre is the centre of mass between two objects. To help

visualise this, if I get a nice butternut squash on one end of a stick and a kiwi on the other end, we can see that the centre of mass is more towards the butternut. For most of the planets, they have a much greater mass than the moon's orbit in them. So the centre of mass in these situations resides within the planet itself. meaning it just wobbles as the moon's gravity tugs on it. With Pluto and Sharon though, they are much more similar in mass, which means the point in which they orbit is outside of Pluto, making it appear like they are swinging around an invisible object in space.

The only other place that this happens with all the other big celestial objects in the solar system is, surprisingly, the Sun and Jupiter. Thanks to the phenomenal mission of the Gaia Sky Survey, we now know that there are at least 300,000 stars within 326 light years of us, and we have recorded their velocity and the direction they are moving through the galaxy. Most stars are heading in the same way, although you'll immediately notice some that are heading in any direction, some leaving the galaxy altogether. Eighty million years into the future, the stars have spread out a lot, but due to what is believed

to be density waves within the galaxy, a lot of the stars are still. stars reconvene at the galaxy's arms. The bright clumps within these stars are star clusters, all of which tend to have the same velocity and direction, meaning that while the cluster stretches over time, generally they stay together. Eventually, the stars that once surrounded us will form a ribbon around the entire galaxy. Uranus is a world of mystery. It is one of the least explored planets in our solar system due to its remarkable distance

from us. Out of all the planets, only Neptune is further away. In 1986, the Voyager 2 spacecraft whizzed by and found out some very interesting information about the planet that wasn't known before. But out of all its unusual characteristics that set it apart from any other planet, its axle tilt is perhaps the most peculiar. To find out the reason for Uranus's weird axle tilt, I visited Michael Brightmore, president of the Gleesorp's Astronomical Society. Visit BetMGM Casino and check out the newest exclusive. The Price is Right Fortune Pick.

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Well, if I can just demonstrate, Sean, using this little prop. When the solar system was formed, it was formed from this great big disk of dust and gas. So everything in the solar system, when this dust and gas solidified into the rocky planets and the gas giants and the ice giants, Everything was perpendicular to the plane that the planets eventually orbited him. So Uranus would have started out like this, you know, as did the Earth and all the other planets. At some stage in the distant past, and probably early, soon after his formation, something hit Uranus, and from going like that, it ended up with an axial tilt of about 98 degrees. So it's now revolving like that.

And of course it's often described as rolling around the sun. And that's what it does all the way around the sun. The Earth doesn't have quite so pronounced an axial tilt, it's just 23 and a half degrees. So the Earth is going round like that, whereas Uranus is just over 90 degrees, and it's actually rotating about its axis in that way. You know, this is very unusual. And it leads to, you know, a lot of considerations. about its weather. The Earth's seasons and weather are all based on our axial tilt.

You know, sometimes the Northern Hemisphere is tilted towards the Sun. That's our summer in the Northern Hemisphere and the Winter in the Sun hemisphere. You know, and as it goes round we go past the Equinox, where it's neither tilted towards or away from the Sun. And then back round the Sun to winter, where the Northern Hemisphere is away from the Sun, that's our Northern Hemisphere Winter and the Southern Hemisphere Winter. the Sun-Nemisphere winter. But it makes you wonder what on Earth the weather would be like on Uranus that's tilted

with often its axis pointing towards the sun. It takes 84 years for Uranus to actually orbit all the way around the sun and back, whereas the Earth does that in just one year. So for a lot of that orbit, its axis and its North Pole is pointing directly towards the sun. and the equatorial regions are getting very little sun. Now that's interesting because it was in that position when Voyager 2 actually flew past it. It had got its southern axis pointing directly towards the sun.

And what Voyager 2 didn't see, which it expected, was a lot of weather patterns on the surface. You know, as we see all the time with Jupiter, we see these lovely bands and vortexes and the great red spot. But Uranus at that time in 1986 was quite bland. You know, there was no cloud structures. It wasn't realised at the time that that was a phenomenon of this position in the sky.

Later on, as it got a quarter of the way around its orbit, you know, in about 2007, the Hubble Space Telescope was looking at it and a lot more weather features started to appear. So, you know, depending on where it is in its orbit, dictates the sort of weather patterns. And it does have weather. I mean it has winds up to 800 miles an hour.

They're largely hidden by the atmosphere, but using different wavelengths such as infrared. You know, we are able to see these now. But unfortunately Voyage 2 didn't get much of a look at them. So that's the actual tilt of Uranus. It's almost on its side and it's like rolling around the sun in its 84 years. then it's 84 year old.

Since Voyager 2, we haven't been back to Uranus. But if there will be future missions, hopefully we'll get more information on why Uranus is the way it is. There are a lot more unanswered questions about Uranus that we haven't got into today, and hopefully as we learn more, it won't only be the planet that is known for being the butt of jokes. A massive thank you to our astronauts on Patreon.

This video had no sponsors. 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. Hey y'all, it's Kelly Clarkson with Wayfair. Ever order furniture online and wonder

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