Astrum Space - The Universe's Most Powerful Explosions

Episode Date: June 16, 2025

A compilation of ‪episodes all about explosions in deep space.Discover our full back catalogue of hundreds of videos on YouTube: ⁠https://www.youtube.com/@astrumspace⁠For early access videos, bonus content, and to support the channel, join us on Patreon: ⁠https://astrumspace.info/4ayJJuZ⁠

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Plus, unlimited plans started $35 a month. Now that's a deal that doesn't stay. Explore GoogleFi Wireless plans today. Plus taxes and government fees. GoogleFi Wireless is not subject to data traffic deprioritization during times of high network usage. Every year since 2018, astronomers have spotted a mysterious blue flash in the sky. It is one of the brightest phenomena in the universe, an explosion that makes the average supernova look like a faintly lit candle in the distance. Some have been spotted closer to us, and others billions of light years away.

They look similar enough to one another, but no one knows what they are or what causes them. Through rigorous observation and analysis, astronomers began decoding a pattern and formulating a tentative but plausible theory, until in 2023 they saw something that left them completely baffled. These explosions are called luminous, fast, blue optical transients. And there's simply nothing else like them out there. I'm Alex McColgan and you're watching Astrum. Join me today as we dive into the mystery of space's brightest explosions, how they were discovered and why they keep stumping scientists again and again.

Being such a recently discovered event, the data we have on luminous fast, Last blue optical transience, or LF bots for short, is minimal. The first LF bot ever detected was identified just six years ago in 2018, and we've only witnessed a handful of them since. As so little is known about them, it makes agreeing on a universal definition a little tricky. For now, what scientists do all agree on are some common characteristics these LF bots seem to share. So far, they all display a predominantly blue emission, very high optical luminosity, and being bright in x-rays, ultraviolets, and radio waves. They are also very fast, as their

name indicates. LF bots go off like a cosmic camera flash. They reach peak brightness and then dim very rapidly, usually in the space of hours or days. As you must be a moment, might note, a supernova follows the same pattern of brightening and then dimming, but this dimming takes weeks or months. This short-lived nature of LFBots makes them difficult to spot and study. So how did we manage to capture such an elusive event? NASA's Atlas H.K.O. Telescope in Hawaii is part of an early asteroid impact warning system that scans the entire sky several times a night for moving objects. On the 16th of June

2018, Atlas H.K.O. was performing its routine scan when he captured something very unusual, a flash, 100 times brighter than a regular supernova that disappeared within days. The scramble was on. Scientists immediately started analyzing the data to understand what they'd seen. They pinpointed the explosion as coming from the Hercules constellation some 180 million light years away. Officially designated AT 2018 cow, the event was affectionately nicknamed the cow after the last three letters in its name. Once located, it was quickly classified as a type 1B supernova.

This kind of supernova, also known as a core collapse explosion, is formed when massive stars collapse under their own gravity. But something about this particular explosion didn't quite fit. When taking a closer look at the cow's emission spectrum, it didn't look very typical for a Type 1B supernova. It had unusually broad emission lines and very weak helium lines. Scientists thought it appeared more reminiscent of a Type 1C BL supernova, and so was quickly reclassified However, the more scientists poured over the data, the more surprised they were by what

they found. Whatever this explosion was, it started to look less and less like a supernova, at least not the kind of supernova we'd expect. For starters, it appeared out of nowhere. This blast went from inactive to peak luminosity in just a few days. Like we mentioned earlier, Supernova usually take a few months to reach their brightest and dim again at a similar pace. Not only that, it was registered to be 10 to 100 times brighter than an ordinary supernova. Also, everything about the way it exploded was wrong. When supernova explode, they tend to release their energy in a spherical shape.

We know now that the shockwave sent out after a supernova can be asphherical, due to the presence of strong magnetic fields, which can distort the shape of the initial blast. However, upon closer inspection, this mystery explosion did not even explode spherically. The researchers themselves called it the most asphherical explosion ever seen. Soon enough, other theories were being put forward. Some thought the cow could be a monster black hole, shedding a passing star. Others suggested it was a supernova that gave birth to a black hole or a neutron star. But let's step back for a moment.

It's really hard to draw any conclusions when you only have one of something. As the saying goes, once is an anomaly, twice is a coincidence, and three times is a pattern. What research has really needed was a bigger sample size, more instances of this kind of explosion, they could compare observations and deduce any patterns that might arise. Luckily, it didn't take long for scientists to get their eyes on a second similar explosion. A few months later, in September 2018, the cosmic camera flashed again. And again, for a third time in 2020. Keeping in the tradition of pulling animal nicknames from the last three letters of their

official names, we had the beginnings of a LF bot zodiac. The cow was joined by the koala and the camel. And just like that, they had data on three separate LF bot events. They could start hunting for patterns. When analyzing the cow, koala and camel, one of the first things that stood out to researchers was the location of these events. Even though they all happened in different parts of the universe, each blast was registered as coming from inside the spiral arm of a galaxy.

At first, this information emboldened the initial theory that LFbots were just a type of core collapse supernova. Let me explain why. The kind of star that causes a core collapse supernova is a massive star, one of the biggest types of stars you can get. And as you know, the bigger the star, the shorter its lifespan. This means that these stars don't get the chance to travel very far before they die. It would make sense then that their supernovae occur very close to the star cluster where they were born. And what part of the galaxy is known for having such clusters?

Yep, the spiral arms. The exact place we saw all three LF bots. But just as researchers seem to be making progress, something happened that caught them completely off guard again. Like the Atlas H.K.O. in Hawaii, the Tsukki Transient Facility is a very wide angle ground-based camera that scans the whole northern sky every two days. In 2022, it detected another similar explosion. Except after the initial blinding flash, this optical transient started behaving rather strangely. Instead of exploding once and fading away

in a few days like the other LF bots before it, the so-called Tasmanian Devil continued to produce short duration bursts far longer than expected. What's more, each of these bursts seemed to be just as bright as the original explosion, which was very strange indeed. The Tasmanian Devil emitted more energy than hundreds of billions of stars like our sun combined. Researchers were deeply puzzled yet again. It was unlike anything they'd ever seen before in astronomy. Now, I know the skeptics among you may be thinking, Alex, this has got to be due to some

kind of technical error, miscalibrated equipment, a fluke in quality control tests, or a simple mathematical mistake. Indeed, the history of science is littered with scientists shouting Eureka at supposed breakthroughs or discoveries, only to be deflated once someone checked their workings. But this is not one of those moments. The data was corroborated by 14 other telescopes around the world. They confirmed that the Tasmanian devil did in fact pulsate a minimum of 14 times. The total number was likely much higher.

surprising, these mega-powerful pulses were only minutes apart. It looked to scientists like a star that kept dying and being revived again and again. If that's what it is, a strange phenomenon could provide brand new insight into the life of stars. So far, stellar life cycles have only been studied as snapshots of different stages, never as a continuous process. In short, even though the multiple bursts of light from the Tasmanian Devil were unexpected, there was still reason to suspect these explosions could have been a strange type of supernova, seeing as none of the observations directly violated the core collapse supernova theory. But what came next did.

On April 10, 2023, astronomers picked up yet another big blue explosion. with all the same characteristics as their LFBot Zodiac relatives, except this one was not even close to where it was supposed to be. Unlike all the other LF bots before it, the Finch was not in the spiral arm of a distant galaxy. Three billion light years away from us, and 15,000 light years from the closest galaxy, it stood solitary in space. was in the middle of nowhere, and exploded between two galaxies.

This was a huge blow to the leading theory. If these explosions really were the result of massive stars core collapsing, there's no way it would be happening in between galaxies. So it was back to the drawing board for researchers. They came up with two new theories to explain what could have caused the finch to explode where it did. The fear suggests that the finch could be the result of stars being torn apart by an intermediate mass black hole, a black hole that has 100 to 10,000 times more mass than our sun. Except the existence of these black holes has never been proven. Their smaller

and larger relatives, stellar remnants and supermassive black holes, have both been confirmed to actually exist. But this mission. child remains purely theoretical. However, should they exist, could they be responsible for this elusive light show? Astronomers have shown in simulations that stars can orbit intermediate mass black holes as many as five times before being ejected. With each orbit around the black hole, the star is effectively being ripped apart by losing more and more mass. Finally, the remaining stellar matter would be flung back out into the galaxy at speeds as high as 10% the speed of light.

This would be consistent with the speed and brightness observed in LF bots, lending weight to this theory. One of the most likely places researchers would expect to find intermediate mass black holes is in globular star clusters in a galaxy's outer halo. Galaxies have halos that extend far beyond the main disc and bulge. They are most visible in spiral galaxies like our milked In our own home galaxy, the outer halo stretches some impressive 1 million light years from its galactic center.

Some scientists think that it is possible that the Finch could have been located inside a globular star cluster such as this. If this is the case, and intermediate mass black holes do exist there, it could be plausible that the Finch was caused by these unusually sized black holes ripping up large stars. The second theory researchers put forward suggested that the Finch could have been the result of two neutron stars moving towards each other in increasingly tight spirals until they collided. This kind of event causes Achillenova, which is known to be one of the biggest stellar blasts in the universe.

One telltale sign of a kilonova is the presence of gravitational waves, which come through as a hallmark chirp, caused by a rapid increase in frequency. as two massive objects spin around each other, eventually colliding and merging. If we could find something like this when analyzing data from the Finch, it would lend strong credence to the neutron stars theory. However, as bad luck would have it, our chirp detector, the laser interferometer, gravitational wave observatory, or LIGO, was down for maintenance at the time the Finch occurred. That means we don't know if such gravitational waves were emitted as we have no data on them.

One thing we do know is that no gamma-ray burst was detected, which is something you might expect to see with a kilonover of this size. But remember, this explosion happened 3 billion light years away. That's really far, perhaps too far for whatever gamma-ray data there might have been to be detected. All in all, none of this data can conclusively confirm or reject the neutron star theory. It's frustrating to bear witness to such an incredibly rare, new, and powerful phenomenon, and not have the data to conclusively understand what is causing it. I guess patience is an underrated virtue for an astronomer to have, but they are not

sitting on their hands either. Scientists are already planning to use the optics of the James Webb Space Telescope to carry out a surge for any faint, globular clusters in the same location as the Finch. This would hopefully clarify if they are on the right path with the intermediate mass black hole theory. In the meantime, other researchers are focused on broadening the sample size. The more LF bots we can detect, the more we will learn about them. The six we have seen so far have taught us some things, but we have a lot left to learn. The only way we're going to get a larger sample is to keep sweeping the sky with wide-field surveys

like the Atlas H.K.O. and the Zviki Transient Facilities hopes are pinned on the Vera C Rubin Observatory, currently under construction in Chile, a telescope which will scan the entire southern sky every few nights, which I've done a video about here. It is expected to be operational by 2025 and will be able to capture 10 times more level. light than all previous facilities. Follow-up observations with Hubble and ground-based telescopes will help analyze more information which could lead to more breakthroughs. LF bots are a super new phenomenon that we still don't understand well.

Scientists themselves admit that the discovery of the Finch raises more questions than it answers. The more we learn about these bright blue explosions, the more they keep surprising us. All there is left to do is what hundreds of generations of astronomers have done for centuries before us. Point our telescopes out to the sky, watch and wait. On the 14th of September 2015, scientists at the Laser Interphometer Gravitational Wave Observatory detected gravitational waves directly for the first time, a stunning achievement that led to the 2017 Nobel Prize in physics. Why was this significant?

Well, here's an analogy. Let's imagine that human beings evolved without the ability to see light. For thousands of years, we'd fumble in the dark, relying on our other senses, until, one day, someone invented a machine that could perceive light for us. In time, we'd see everything from the tips of our noses to the farthest flung galaxies. This analogy captures the magnificence of LIGO. It's about much more than proving a scientific prediction. LIGO enables us to perceive the physical universe and understand reality on a new level. Like photons, gravitational waves travel at the speed of light as they ripple across space-time.

Their signals are all around us. By listening for gravitational waves with some of the most sensitive instruments ever built, scientists are recording tremors of distant, violent events. events, the formation of black holes, supernova explosions, and potentially exotic phenomena we haven't discovered yet. So what are gravitational waves? What causes them? And why is LIGO's ability to detect them already transforming our understanding of the universe?

I'm Alex McColgan and you're watching Astrum. Join me today as we learn about gravitational waves. unpack the groundbreaking technology behind LIGO and anticipate some of the stunning developments that lie around the corner. Gravitational waves are one of the stranger implications of Albert Einstein's general theory of relativity. As we've covered previously, space-time is a model that combines the three dimensions of space and the fourth dimension of time into a single manifold. All objects with mass create curvature in space-time, and objects with a lot of of mass create a lot of curvature, which we experience as gravity.

The simple way to visualize this is to think of a pool ball resting on an elastic surface and a bowling ball resting on that same surface. The more massive bowling ball will create more curvature. As objects move across space-time, that curvature changes position with them. One of the amazing consequences is that when objects of a certain mass accelerate, iterate, they can send ripples across space-time as gravitational energy. While this requires a special set of conditions, namely a very massive object undergoing acceleration, such a cataclysmic event would send ripples, or gravitational waves outward at

the speed of light. Think of them like ripples on a pond, but instead of water, they travel through the fabric of space-time in all directions. As in the pond analogy, these disturbances become weaker as they radiate outward. To an observer, the distance between objects would appear to expand and shrink as the gravitational wave passes. Mind-boggling to imagine. Yet, although Einstein predicted the existence of gravitational waves, he was pessimistic

about our chances of ever detecting them. He thought that these disturbances would be so small as to escape our ability to measure them. And who could blame him, many of the changes in distance that LIGO seeks to measure are one 10,000th the length of a proton. Yes, you heard that correctly, 10,000 times smaller than a single proton. And yet, these signals would come encoded with all kinds of information about their origins, when they originated, how far they travelled, and what kind of event produced them. This is where LIGO comes in.

It consists of two observatories funded by the United States National Science Foundation and operated by MIT and Caltech. Among its driving forces are renowned physicists Kip Thorne, Raina Weiss, and Barry Barish, all of whom share the 2017 Nobel Prize for their decisive contributions to the detection of gravitational waves. So, is essentially a large-scale and very sensitive interferometer, an invention that's been around since the 1880s. An interphorometer essentially measures what happens when light waves are combined from two or

more sources. For example, you could use an interferometer to test whether light travels at different speeds through different substances, such as through air or water. Even a subtle difference in speed will produce an interference pattern when the light waves combine, much like what happens when two ripples on a pond intersect. If the peak of one ripple hits the value of a second ripple, they will subtract from each other, producing a flat surface. However, if the peaks line up exactly, it means that the waves are in phase and add to each

other. This is essentially what the interferometer measures with light. By seeing how in or out of phase two light waves are, an observer can infer the relative speed of the waves, and the larger and more powerful the interferometer, the more sensitive it is. Here's how it works. LIGO has two observatories, located in Hanford, Washington, and Livingston, Louisiana. Why too?

Well, you need at least two detection sites to triangulate where the signals are coming from. Each observatory continuously fires a powerful laser at a beam splitter positioned at a 45-degree angle. The laser beam has to operate at around 750 kilowatts, powerful enough to vaporize you completely if you've got in its path. The splitter then splits the laser beam perpendicularly. The light in each arm travels down a 4km vacuum cavity with a mirror at the end of it. The beams then bounce between this mirror and the recycling mirror at the other end nearly 300 times, increasing the distance from 4 to 1,200 kilometers. Remember what we said, with interferometers, bigger is better. After completing nearly 300 trips,

the laser beams combine at the beam splitter and head to a photodiode, which is a light-sensitive semiconductor. If undisturbed, the beams will be in phase, meaning their frequencies will will subtract each other, and no light will arrive at the photodiode. But if there's a gravitational wave, the distance each beam travels will be slightly different, and they'll be out of phase. The photodiod will pick up a signal indicating the presence of a gravitational wave. Now, this is how it works in a perfect world, but in reality, the interferometer is constantly picking up noise.

To minimize this, LIGO uses incredibly smooth 40-kilogram mirrors suspended by silica threads. Any particles in the interphotometer's arms are also a problem, which is why LIGO pumps the air from its vacuum chambers to one trillionth of atmospheric pressure. But there's another problem. At these minuscule levels, even quantum mechanics are a nuisance because they introduce randomness into photon behavior. LIGO mitigates this with an optical cavity which squeezes the light. This squeezing minimizes the light phase's noise and squeezes it into amplitude noise,

which the interferometer doesn't measure. In other words, the quantum randomness will show up more in the height of the waves. Quantum randomness is a fact of life. It can't be eliminated, but it can be shifted, much as you might move from the waves. clutter from your bedroom floor to your closet. The chaos isn't gone, just out of sight for the moment. Plus, the goal isn't to eliminate noise completely, but to get the best signal-to-noise ratio possible. That's a pretty good overview of how LIGO works. So what has it discovered? As I mentioned earlier, LIGO detected its first signal in 2015. Named GW-150914, scientists studied the

data and learned that it was caused by the merger of two black holes, about 1.6 billion light years away. These black holes, which were 29 and 36 solar masses, became a binary and spiraled around each other until they merged and released a blast in the final 20 milliseconds that was so powerful. Now get ready for this number, because this is what the scientists actually think. contained 50 times the combined light power of every star in the observable universe. At the risk of sounding crude, that is nuts.

I've read this fact many times over, and I still cannot comprehend what it means. Yet, after travelling for 1.6 billion years and finally reaching LIGO, the disturbance was so faint it moved LIGO's 4 km-aum 1,000. of the width of a proton. To visualize this, imagine the distance between us and Proxima Centauri and changing it the width of a human hair. That is the level of precision LIGO was able to detect. If that's not one of the most astonishing feats in human history, I don't know what is.

And this was just the first gravitational wave LIGO detected. The second detection occurred three months later in December 2015. That signal also came from a black hole merger, which took place 1.4 billion light years away. Over its initial three runs, LIGO recorded more than 80 black hole mergers, and in August 2017 it detected the merger of two neutron stars. Named GW-170817, this signal was notable for being the first gravitational wave to be corroborated by electromagnetic observations from 70 observatories across the planet.

This was a breakthrough, not only in gravitational wave detection, but in multi-messinger astronomy. It turns out, LIGO was just warming up during these three runs. As of May 20203, LIGO has begun its fourth run with better sensitivity than ever. After its latest round of upgrades, which kept LIGO offline for three years, the observatories now have more reflective mirrors, better mirror suspension, and improved light squeezing with lower quantum uncertainty. And this time, LIGO also has the support of Kagra, a new interferometer observatory in Hida, Japan.

Kagra is located underground, making it the world's first subterranean gravitational wave observatory, and also the first to use cryogenic mirrors. During an engineering run on the 18th of May, LIGO scientists say they already received a signal that was possibly caused by a neutron star being swallowed by a black hole. We'll have to wait a while for confirmation, but if these early results are any indication, LIGO is about to blow the doors off our understanding of gravitational wave-generating phenomena. So what other developments lie ahead? India is preparing a collaborative project called LIGO India, or Indigo, which will help LIGO

triangulate better location data. In 2027 to 2028, LIGO will implement its LIGO Voyager upgrade, which will achieve higher sensitivity with four times heavier mirrors and higher frequency lasers. And in the more distant future, a third-generation facility has been proposed. called Cosmic Explorer. This facility would feature two new observatories, with arms spanning 40 kilometers and 20 kilometers respectively. Remember, with interferometers, bigger is better.

But the proposal that really excites me is the laser interferometer space antenna, or Lisa. This would be the first space-based gravitational wave observatory, which would utilize three spacecraft in a 2.5 million-kilometer-long configuration. This interferometer would be so big and so precise, scientists hope it would be adept at uncovering exotic and theoretical sources of gravitational waves, such as cosmic strings and other speculative phenomena. In theory, it could help us stare directly into the fabric of reality. With a planned launch date of 2037 were still over a decade away, but it's never too early to start

counting the years. So there you have it. An overview of LIGO and how scientists are using gravitational waves to better understand the universe. They give us evidence of extremely remote and ancient phenomena that cannot be measured by other means, and they can be a secondary way to measure observations made by other instruments, the Web Telescope or Hubble. In time, this revolutionary field should allow us to understand the nature of our universe, its history, and even its future. I hope you found this episode

as fascinating as I have. In October 2022, a brilliant flash pierced the cosmos, brighter and more intense than anything human civilization had ever seen. And that's not an exaggeration. The strength of the The blast blinded our gamma-ray detectors the world over and unleashed more energy in a matter of seconds than our sun will emit over its entire 9 billion year lifespan. Over the 18 months that followed, it became the most widely studied gamma-ray burst in history, creatively dubbed the boat for the brightest of all time. As researchers began to decipher its cause, their findings unraveled one mystery after another. Scientists have been cataloguing gamma ray bursts for decades, but this one was closer, brighter,

and unexplainably devoid of some key signatures you'd expect to see. It also raises some far-reaching questions about our standard model, the possibility of a dark matter particle, and how heavy elements like gold are made. I'm Alex McCulligan, and you're watching Astrum. Join me today as we dive into the mystery of the biggest and brightest gamma-ray burst of all time. What caused such a colossal explosion? How is it different from other gamma-ray bursts before it? And what can it teach us about our understanding of the universe and the particles that constituted? Where's your playlist taking you? Down the highway, to the

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Listeners of this show will get a $75-sponsored job credit at Indeed.com slash podcast. That's Indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. Gamma ray bursts are brief, intense flashes of high-energy gamma radiation lasting from milliseconds to several minutes. The first of its kind was detected in 1967. when American satellites designed for detecting covert Soviet nuclear testing picked up an unusual pattern of electromagnetic energy. Since then, gamma-ray bursts have been of tremendous interest to the cosmological community, as they allow scientists to study states of matter and physics that are not reproducible on Earth.

Essentially, they provide researchers with a glimpse of how stars are formed and evolve across the whole timeline of the universe. There are two different kinds of gamma-ray bursts. Short gamma-ray bursts last less than two seconds and are attributed to either the collision of two neutron stars or the merger of a neutron star and a black hole. They can be followed by a Kilo Nova, an emission of bright light resulting from the radioactive decay of chemical elements. This decay creates even heavier elements, an important feature of Novi, which we'll discuss more later. Anything lasting, Longer than two seconds is classed as a long gamma-ray burst. These are thought to be caused by the explosive deaths of massive stars and their subsequent supernovae.

The collapse core may form either a neutron star or a black hole. These typically occur close to the edges of the observable universe because they are characteristic of low metallicity stars which formed when there were less heavy elements around. When we see one of these, we are witnessing events from billions of years ago. In the case of both long and short gamma-ray bursts, the newly formed black hole blasts out jets in opposing directions, containing particles accelerated close to the speed of light. When these particles interact with surrounding matter, they emit the gamma rays we detect. So what made the boat so special?

Let's start by analyzing some of its key characteristics. Firstly, the boat lasted 10 whole minutes and was detectable for 10 hours after the fact. It occurred in the Sagita constellation only 2 billion light years away, which is much closer than other gamma-ray bursts we've detected until now. In fact, such a bright explosion so close to Earth is thought to be a 1 in 10,000 year event, meaning the last time one happened, humans had barely started farming. As is the case with other long gamma-ray bursts, we know a collapsing and exploding star was behind it, but this is where things start to get fuzzy.

A supernova alone isn't enough to explain the magnitude of the gamma rays emitted. The boat was a whopping 70 times stronger than any other gamma-ray burst detected. the theory was that this must be the supernova of a ginormous star, the likes of which we rarely see. However, upon closer inspection of the afterglow, scientists found that the supernova behind the boat was shockingly ordinary. To get a clearer picture, astronomers pointed the James Webb Space Telescope in the boat's direction. Webb's near infrared spectrograph revealed that the supernova behind the boat was actually pretty average. It wasn't nearly as bright as you'd given the gamma-ray burst that accompanied it.

So what could have caused such a flash? One idea is that we simply perceive the flash as bigger and brighter because of Earth's relative position to the blast. Imagine a flashlight shining in the dark, diffuse and soft. It lights the path one to two meters ahead of you. Now, imagine capturing all that light and focusing it into a singular laser beam. It wouldn't illuminate the path as widely, but it would reach hundreds of meters into the distance.

And if Earth was in the direct path of that laser, it would register a super bright reading. That doesn't mean the laser released more energy than the flashlight. It just means the way it was concentrated and then detected resulted in higher reading. The same concept can be applied to these gamma-ray bursts. If a massive star is spinning super fast when it collapses, then the shape and structure of the near light-speed jets it emits will be more narrow and focused, and therefore brighter. In fact, the jets seen from the boat are some of the narrowest we've ever seen.

But not only were these particle jets brighter than expected, scientists also detected way more of them going faster than expected. They traveled with such fervor that after two billion years traversing the cosmos, they arrived here and momentarily disrupted the Earth's atmosphere. Sitting just 50 to 1,000 kilometres above the surface of our planet, Earth's ionosphere is rich in electrically charged particles. When the boat struck, it left a mark comparable to that of a major solar flare, pushing the ionosphere down into lower altitudes. If photons from an explosion, 2 billion light years away, can have this kind of effect on our planet,

I don't really want to think about what happens if something like that in our neighborhood explodes. The large high-altitude air shower observatory in Dowicheng County, China managed to capture data on tens of thousands of photons over the course of the initial blast and into the afterglow. This is a quantity unlike anything seen before in gamma-ray astronomy. In fact, it's so far out of pocket that some astrophysicists think that they might be pointing towards something missing from our models.

According to our current understanding, it's very unlikely these super high-energy photons are travelling for 2 billion years. Cosmic microwave background radiation, interactions with intergalactic dust, or redshifting caused by the expansion of the universe are all factors that can interfere with the photon's trajectory. One hypothesis put forward is that photons convert themselves into a hypothetical particle called an axiom, and then convert back into gamma rays upon reaching our galaxy's magnetic field. Axions are thought to be an ultra-light particle responsible for dark matter.

Their existence is currently purely hypothetical. We have no evidence for them, and even if we did, they would lie outside the standard model of particle physics. We don't have time to delve into detail in today's video, but let me know if you'd enjoy a separate video on this in the comments. Okay, so far we've established that boat was caused by a massive star collapsing and turning into a black hole, which incidentally is known as a collapsar. Aside from generating a long gamma ray burst, collapsears are also known for generating something else. Gold. Wait, wait, how is gold connected to gamma rays? Good question.

To understand that, let's take a minute to discuss. how elements are made. The core of a star is a super high pressure environment, some 200 billion times higher than the atmospheric pressure on Earth. In these conditions, nuclear fusion reactions create heavier elements out of lighter ones. For example, one helium atom comes from fusing four hydrogen atoms together. Elements 2 through 26 on the periodic table, that's helium to iron, are made this way.

are made this way, for process known as stellar nucleosynthesis. However, once you get to iron, it isn't energetically favourable to continue making bigger and bigger elements this way. So how do we account for the rest of the periodic table? Where do these heavier elements like gold come from? At the moment, we know two different ways these elements are formed. The first was recently confirmed by the James Webb Space Telescope, when two ultrously In the dense, neutron stars collide, they emit an immense amount of neutron particles.

The surrounding material captures these neutrons, making their atoms temporarily unstable. In order to stabilize, the neutrons undergo radioactive decay into protons, creating new, heavier elements. This process is known as rapid neutron capture, or R-processed nucleosynthesis. Some calculations suggest one neutron star collision can produce up to three. three earth masses worth of heavy elements. However, this explanation alone isn't sufficient to account for all the heavy elements in the universe.

Neutron star collisions are rare, and take a long time to happen in the order of billions of years. On top of that, observations of very old stars show that heavy elements were already present in parts of the universe well before most binary neutron stars would have had a chance to collide. So how do you explain that? There must be another source of heavy elements in the cosmos, which brings us back to our boat. There's another theory that collapse stars like the boat could be another source of our process nucleosynthesis.

In their dying stages, massive stars like the one that caused the boat are surrounded by layers of exploding gas. These explosions leave disks of matter swirling around the resulting infant black hole. As the black hole begins devouring the surrounding material, it can only ingest so much at a time. What it cannot manage is swept away in a neutron dense wind. Here, the same R process nucleosynthesis occurs, forming heavier elements like gold, silver, and platinum.

This seems promising. But unfortunately, even factoring in these kinds of things. kinds of supernova isn't enough to account for the abundance of gold in the universe. To make matters worse, analysis of the boat spectrum didn't show any traces of heavy elements, raising questions about the validity of this collapsar gold-making theory. Some scientists suggest the boat's host galaxy might have something to do with the lack of heavy elements in the explosion. Upon modeling the host galaxy spectrum, researchers discovered it has the last

lowest metallicity of all previous host galaxies where gamma-rate bursts were detected. In other words, maybe the environment didn't have the right building blocks to make heavier elements. How do we know how much gold should be out there in the first place? How do scientists predict something like the relative abundance of elements in the universe? There are two main methods of calculating this. The spectroscopy of stellar photospheres and meteorite analysis. By analysing the absorption lines in the spectra of stars, astronomers can determine the relative

abundances of elements in the photosphere of those stars. The composition of meteorites, remnants of an early solar system, are analyzed in parallel to determine the relative abundances of elements. Meteorites are especially useful for measuring the abundances of volatile elements like hydrogen, helium, and noble gases that are unrepresented in stellar photospheres. The results of both of these methods are usually congruent, indicating we're probably doing something right. But this is physics, so of course nothing is so cut and dry.

One famous exception to this rule is lithium. According to the standard Big Bang nucleosynthesis theory, the early universe should have produced about three times more lithium-7 than is currently observed. The plot thickens when we consider its isotope, lithium 6, where we observe 1,000 times more than our predictions can account for. This discrepancy is known as the lithium problem and remains unsolved, presenting a significant challenge to the standard cosmological model. It highlights the importance of understanding the processes that shape the relative abundances

of elements in the universe and suggest that our current understanding of nucleosynthesis might be incomplete. Just because boat didn't yield gold as expected doesn't mean we should discard these kinds of extreme gamma-ray bursts as places where heavy elements could be made. Observations of nearby stars have provided strong evidence for an early R process that enriched the universe with heavy elements. But the boat findings cannot be ignored,

as they suggest there may be alternative, currently unknown processes responsible for this elemental enrichment of our cosmos. The results may call into question our entire model of understanding regarding collapsars and their role in creating heavy elements. This discovery is much bigger than just the boat or gamma rays. It's about the literal building blocks of our universe as we know it. Where do our different atoms come from? And why do they exist in the proportions they do? How much of our model is accurate and how much is missing? What role does dark matter play in all of this?

We need more time and research before we know for sure, but the boat is a great example of how new findings keep our understanding of physics ever evolving, just like the universe itself. Imagine for a moment that you're looking out your window when a singular bright light suddenly flares into existence in the sky above you. This dazzling star is as luminous as the light, full moon at night, perhaps brighter, and is even visible during the day.

If you can see the light, you might already be in trouble, as that unexpected star is now flooding the atmosphere of the Earth with a catastrophic dose of gamma radiation and x-rays, stripping away our ozone layer and exposing us to the full fury of the sun's deadly radiation. And on its way, jettisoned out at 10,000 to 40,000 kilometers per second, a cataclysmic wave of stellar matter and debris hurdles towards our planet. The dying roar of an exploding star venting billions of tons of burning mass at us, ready to sweep across our planet's surface in a tidal wave of fire. This is a supernova, or at least it's one interpretation of what we might see if one were to occur

near us. But how likely is it for this to actually happen? What constitutes near us on a cosmic scale? How close would a supernova blast have to be before life on Earth would be threatened? What might we on Earth actually experience? And what stars near us have the potential to detonate in this way? USAA knows dynamic duos can save the day, like superheroes and sidekicks or auto and home insurance.

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Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion. I'm Alex McColgan and you're watching Astrom. Join with me today as I discuss an event that could be an Armageddon in our lifetimes. Or could be nothing more than a pretty twinkle in the sky. Let's start with the good news. Supernovae in our galaxy are not that common. While astronomers observe hundreds of supernova every year outside our galaxy, this is mostly

a reflection on how many galaxies there are in the universe. Closer to home though, within our own Milky Way, we likely only see about two to three every century. This means that the odds of one going off tomorrow are not that high. But they're not impossible, and according to archaeologists, the Earth has likely been hit by a supernova before in the course of its four. 4.5 billion years of existence. For starters, we exist in an area of space known as the local bubble, a relatively sparsely populated

region of interstellar space about 1,000 light years across that is thought to have been carved out by a supernova detonation 10 to 20 million years ago, which our planet would have been around for. I talk about that in another of my videos which you can see here. Scientists have found evidence of another detonation that happened to an 1.5 million years ago, due to a high concentration of iron 60 and manganese 53 in a particular layer of the geological record. This supernova happened far enough away to be harmless to us, but this might not always be the case. There are some scientists who believe that the extinction

of woolly mammoths was caused by a massive piece of debris from a supernova crashing into the planet about 13,000 years ago. The impact site in question had magnetic sphurals and radio, radioactive potassium 40, a substance found in supernova ejector. A smoking gun in the era most mammoths went extinct. Even before that, mammoth tusks from 34,000 years ago were found containing tiny impact craters from grains of slightly radioactive iron that had been travelling at 10,000 kilometers per second. If you can recall, that was one of the potential speeds supernova explosions travel at. can't have been a nice experience for the mammoths in question.

An astute observer from this might be able to note an important fact, however. Evidently, if life began on Earth about 3.7 billion years ago, and we faced three supernova explosions that have impacted us in the last 20 million years, and life is still largely ticking along, my condolences, woolly mammoths, if you did die out from one of these, then supernovae as a whole can't be quite as destructive as my over. opening introduction made them out to be. And that's largely true, although it is of course a question of proximity. If I'm 1,000 kilometers away from a nuke going off, I have little to fear.

But it's a different story if one detonates on my coffee table. And when it comes to supernovae, it turns out that the universe has relatively large coffee tables. To understand the scale of these explosions, it's necessary to understand the forces involved. which means we need to understand a little better about how supernova happen. It turns out that there's two main paths stars can take to get to that explosive grand finale, although in each case it has to be the right kind of star. For the first path, resulting in a Type 1A supernova,

it usually needs to be a white dwarf in a binary system that's gradually or speedily siphoning matter away from its neighbouring star until it reaches a point of critical mass. This path is not fully understood, but it's thought that a white dwarf, or a dense star comprising of mostly carbon in a giant super diamond core, is normally finely balanced between two powerful opposing forces,

electron degeneracy pressure and gravity. This simply means that atoms usually object to being squashed too much. Their electrons like to remain at certain distances from the nucleus of the atom and will resist being pushed denser than this point. But gravity is an incredibly powerful force that seeks to draw matter closer, particularly in a dense mass like a white dwarf, where a section the size of a sugar cube has the mass of around a car. And in a binary system where the white dwarf is absorbing

more and more matter from its neighboring star, eventually gravity overwhelms electron degeneracy pressure, and the whole house of cards collapses at once. Carbon fusion begins. Within a few seconds, most of the star undergoes fusion, forming into heavier elements and releasing a whole lot of energy as the matter in the star settles into its slightly more efficient new configuration. How much energy? Around one quarter-wroughtycillion joules.

That's one followed by 45 zeros. If you claim you knew that number before, you're almost certainly a liar. All of this energy is released in just a few seconds. So naturally, the star ejects its entire contents out in all directions, sending it travelling at 6% the speed of light and unleashing a flood of mostly gamma radiation out across the galaxy. The brightness of this event is 5 billion times brighter than our sun, and burns for a few weeks. until the ejector has travelled far enough that the overall energy level has started to dissipate.

The second type of supernova, type 2, is similar, except instead of involving a white dwarf, it involves a massive star, at least five times more massive than the sun at the end of its lifetime. These stars are still burning brightly, and rather than just electron degeneracy pressure, it's also the heat of fusion that keeps the star in balance. However, just like a Type 1A supernova, eventually balance collapses. This time is because the star runs out of fuel, and without this additional fusion energy pushing

the star's mass outwards, electron degeneracy pressure on its own can't cope with the star's weight to similar effect. The only difference is that while some of a massive star will remain, often collapsing down into a neutron star or a black hole, white dwarfs usually vanish completely. Either way, the scale of material and energy released by supernova is vast, so vast that unsurprisingly, anything immediately next to it is not going to last long. This is an energy powerful enough to rip apart a star. A planet is going to have no chance if it's in the immediate vicinity.

Our own sun, thankfully, will never go supernova, as it's not massive enough, but if it did, there is a good chance the Earth would be either partially or completely vaporized, its rocky exterior reaching a boiling point thanks to temperatures 15 times hotter than the surface of our sun and being whisked away in the weeks of the supernova's passing. What is surprising, however, is how quickly this first wave of devastation would dissipate with distance. Indeed, favourisation is realistically not the largest threat supernova poses. In 2011, experts from the University of Cambridge calculated that even planets orbiting their star at the distance of 15 billion kilometres, or about 100 times the distance between the Sun and the Earth,

would remain intact and would instead simply be sent flying out into space now that there was nothing much left to orbit. Of course, such a planet's hyper-stance. a hypothetical ecosystem would probably have different problems to worry about. Things would get very cold, very quickly. Of course, even if the crust of a planet itself remained intact, that doesn't mean that life on said planet would be sustainable. Ignoring the light of a supernova outperforming the brightness of an entire galaxy sometimes, leading to blindness for anyone who saw it.

Simply stripping away our atmosphere would carry problems. levels of radiation, even if it didn't affect us directly, would alter the chemical composition of our atmosphere, negating our ozone layer, vastly increasing our odds of dying of radiation poisoning, and killing our phytoplankton in the ocean, and causing mass extinctions as the consequences of that worked its way up the food chain. Scientists put this kill zone to be within 25 light years. Beyond that, the fury of a supernova begins to calm, as a distance causes a it to wear itself out.

Although admittedly, the asteroid that potentially killed the mammoths came from a supernova that was 250 light years away, if it happened at all, it was likely bad luck. Generally speaking, we wouldn't notice any damage from a supernova this far away, its radiation levels wouldn't be high enough to cause mass extinctions. By 500 light years, we'd hardly notice the event at all, other than perhaps seeing a brighter star in the sky. Which leaves one important question. Within 300 light years, are there any supernova candidates we need to worry about?

Thankfully, scientists are fairly confident that the answer is no. Massive stars are very noticeable, and the only two that are at risk of going supernova are Beeljuice and Antares. Both of those are more than 400 light years away. White dwarfs are a little trickier thanks to their diminished brightness. they've been conventionally hard to spot, making it harder to predict whether we might be at risk from them. However, in 2013, Issa's Gaia Space Observatory released a massive packet of information in its efforts to map the stars that allowed scientists to identify 13,000 white dwarf

stars within 326 light-years of us. Thankfully, in spite of this large number, scientists remain confident that none of these are scheduled to explode anytime soon. meaning within the next few hundred thousand years. Speaking of Beetlejuice, there are some scientists who predict that this red giant might detonate much sooner than that, perhaps within the next few decades. Their research works under the assumption that Beetlejuice has a much larger radius than previously predicted, but if it's true, it might mean that we would get to see a local supernova within our lifetimes. Of course, according to some models, we would have no nothing to worry about. The shockwave travelling out from Beetlejuice would take some time

to get to us, and even once it arrived, it would be travelling with less force than the push of the solar wind. In other words, it wouldn't be our magnetosphere or atmosphere that kept us safe. The protective sheath of the sun's heliosphere would be enough to keep such a supernova abey. So there you have it. While supernovae are perhaps some of the largest explosions in the universe, through some fortunate stroke of luck, our patch of galaxy has nothing really to fear from them. The odds of us being hit by even the neighboring stars like Beetlejuice that are scheduled to go supernova are incredibly small.

True, Earth has plenty of cataclysms of its own, such as floods, earthquakes and hurricanes that can bring devastation to a community in a heartbeat, and space is still a dangerous place. But it's nice to know that of all the things we have to worry about, we can probably cross planetary annihilation from supernova off our list. The search for alien life is a difficult one. How would we know that aliens exist? An obvious answer would be if they visited our planet en masse, if, like in the film Independence

Day, their sources floated above every city in the world. Or perhaps if their envoys met with us, shaking hands with our world leaders, while cameras broadcast at the moment on national television. Or maybe if they started trading with us, and their inventions and resources began appearing in our everyday life. There is, fortunately or unfortunately, not much evidence that this has ever happened. But while visits from aliens would certainly be preferable, that's not the only possible way aliens can prove their existence to us. It's much more plausible that they would do so with their signals. We've spent a lot of time on this channel discussing some of the reasons why aliens

might not have talked to us, but on the flip side, what are the strongest pieces of evidence that they have already done so? Which signals are considered the best candidate so far for a message from an alien civilization? I'm Alex McColgan and you're watching Astrom. And rather than explain why we haven't heard from aliens, today let's look at where perhaps we already have. Obviously, when it comes to alien signals, there is some ambiguity as to what exactly we are looking for. Aliens are, after all, alien.

We are not quite sure what to expect from them, as they will have likely evolved in conditions different to our own, and may well have cultural outlooks that make perfect sense to them, but are completely obscure to us. Their definition of a good way to say hello to the universe might be very different from hours. Researchers looking into possible signals from other planets have to remain very open-minded about what an extraterrestrial signal might look like. But that means such signals can get confused with signals from natural sources that we simply do not understand yet. How can we tell the difference? Let's look at a few examples to show you what I mean. In 2019, as part of the

Breakthrough Listen initiative, the Park's Marie-Yang Telescope in Australia was observing Proxima Centauri, the star nearest to our own. It was recording data to learn more about stellar flares. But when SETI researchers, a collective term for the search for extraterrestrial life, went over the data it had collected sometime later, they found something unusual, A signal, which later came to be known as BLC1. Could the star closest to our own actually harbour advanced alien life? The signal was fascinating, as it could not easily be explained away by conventional sources. It lasted for several hours, which is longer than the time it normally takes a human satellite

to pass by overhead. It had signal drift, its frequency was shifting, which implied possible movement relative to the telescope, so it likely wasn't coming from a stationary object creating interference on Earth. One of the most compelling things it had going for it was its thin, narrow-band signal. In nature, radio waves are never so narrow in their range. They always fluctuate. Unless there exists some natural source out there we've not discovered yet, the only thing that produces such a concise signal as this is technology, either human or alien. When no obvious explanations for existence could be found amongst human sources, naturally scientists wondered,

could this be the signal from alien life they had been looking for? Along with the wow signal, which we looked at in a previous video, BLC1 is one of the strongest candidates for signals that may have been created by alien civilizations. And yet, even this signal has its drawbacks. Scientists could not link it to any sources of obvious images. interference from technology on Earth, but on closer examination of the data, it did match other radio wave signatures that came up on other days of the search, except these other signals occurred no matter what direction the telescope was pointing in. Neither were they able to detect

BLC1, the signal from Proxima Centauri, with later observations. So while they don't know exactly what interfered with the telescope to produce BLC1, the odds of it being interference are nonetheless quite high. Let's take a look at another candidate, a somewhat mouthier, SHGB02 plus 14A. When one of the first SETI experiments, Project Osmer, was started in 1960 by Frank Drake, it began on the basis that if alien life were to communicate with the rest of the universe, they would do so at frequency 1420 megahertz. The logic behind this was that this was the frequency emitted commonly by hydrogen, one of the

most widespread elements in the universe. Aliens looking to establish communication with other civilizations might use such a frequency as a sort of common ground, a wavelength that probably holds a special significance to any race. This might have been a leap of logic, but it certainly made SHGB 02 plus 14A of interest later, because This signal, let's just call it SHG for the rest of the video, for the lack of a punchier name, did indeed broadcast at this exact wavelength. SHG was spotted on three separate occasions in 2003, using the Arecibo telescope and the computational power of 5.2 million home computers as part of the SETI at Home Initiative, a rather cool

program that is sadly no longer running. S.H.G. had no obvious explanation for his origins in nature, and it didn't appear to be interference. But it was also too weak to say for sure whether it was clearly technological or not. On top of that, its location was peculiar. It came from a spot devoid of stars up to 1,000 light years away from Earth, and although it experienced drift, it did so in a manner that made scientists suspicious. If a signal originates from a planet, then there are a few things we might reasonably infer. A signal being broadcast from a planet, either on the surface or an orbit just above it,

would likely experience some Doppler shift as it alternated from moving away from us to coming towards us through the circular path it was taking in space. There would also be movements where it dropped out of view entirely as it moved behind the planet. While SHG did indeed experience fluctuation in its signal frequency, ranging from 8 to 37 hertz per second, this would only come from a planet that was rotating 40 times faster than Earth, which seemed high. It was also strange that each time the signal was spotted again, no matter where it had been when it had last been sighted, it always began at 1-420 megahertz.

The odds of you looking at an orbiting transmitter on three separate occasions and each time spotting it starting off at the exact same location is incredibly slim, which is what you'd need for this to make sense. This observation pointed to it being, more likely, SHG was some kind of glitch in the technology. By looking at the process by which the BLC1 or the SHG signals were evaluated, we gain an interesting insight into how setty determines whether something might be of alien origin. To me, it is a method that lines up best with this quote from Sir Arthur Conan Doyle, in the words of his famous detective Sherlock Holmes.

When you have eliminated the impossible, whatever remains, however improbable, must be the truth. Each time researchers came across a new signal, they began by eliminating all possible alternatives. Could it be interference from passing satellites? Is there anything in nature that we know of that could be producing this effect? Can we in any other way explain why this signal is here and behaving the way that it does? So far, alternative explanations have been found for these contenders for alien communication. Even on the occasions where human interference can be ruled out entirely, that still leaves open the possibility that these mysterious signals might just be undiscovered

natural phenomena. and that is precisely the current discussion around the last candidate for alien signals I'd like to leave you with today, fast radio bursts. If an alien civilization were ever to be detected, it might not be intentional on their part. Powerful engines activating or beams firing all might release bursts of energy that give away a galactic civilization, which makes fast radio bursts or FRBs interesting. They are, just as the name suggests, very fast bursts of radio waves. We have detected hundreds of these strange millisecond-long bursts across the sky.

Scientists theorized that there might be thousands of them occurring every single day. They have mostly been detected outside our galaxy, but one was detected within the Milky Way in 2020, so they're not completely foreign to us. They seem to be coming from extremely powerful magnetic fields. And as of yet, scientists have no clear idea about what their origin might be. There are plenty of theories. Perhaps they are emitted by neutron stars, or maybe black holes. But there is no proof that puts any one theory over another, including that of alien technology.

The Chime Telescope in Canada has a unique design that makes it ideal for detecting these fleeting blips in the cosmos, Avoiding the pitfall of other telescopes, rather than pointing at any one point in the space, Chyme's multiple cylindrical parabolic reflectors are able to draw data from an entire swath of the sky at the same time. It began detecting in 2018 and is still going strong to this day. It has detected FRBs that are repeating, as well as one that is definitely associated with a magnetar star. Perhaps all FRBs can be associated with such stars.

Perhaps not. But that is just the point. Perhaps one day we will be able to identify the origin of all FRBs and will know that they have a perfectly natural origin. Perhaps the search for alien life will have to begin afresh. But there is always that tantalizing hope, that slim possibility that one day a scientist rule out signal after signal that finally one will come in that defies alternative

explanation. If all other explanations can be ruled out, we can say for certain that no natural source caused this. Then, in the words of that great detective, we will have no choice but to accept the improbable. So, these are some of the best candidates for signals from another planet, but even they come with massive strikes against them. We have not yet found a signal that conclusively points to the existence of aliens. But that is not to say that we, never will. It's never aliens, right up until the moment where it is. Thanks for watching! I was honestly blown away by all the incredibly kind comments and messages you've sent me,

and by the numbers of you that signed up to the Patreon. Like I said in the replies to your DMs on Patreon, everyone here at the Astrum team is so grateful to have such an amazing community. If you haven't joined the Patreon party yet, we're still on our long-term thousand patron member drive, so you can go to the link in the pin comment to become a part of that effort. When you join, you'll be able to watch the whole video ad-free, see your name in the credits, and submit questions to our team. Meanwhile, click the link to this playlist for more Astrom content. I'll see you next time.