#stellar nucleosynthesis

[charyou-tree]

I need people to understand that Uranium is an eldritch horror

I'm not talking about radiation, or nuclear weapons, or anything that you can do with uranium, I mean its mere existence on Earth is a reminder of cosmic horrors on a scale you can barely conceive of.

When a nuclear power plant uses Uranium to boil water and spin steam turbines to keep the lights on, they're unleashing the fossilized energy of the destroyed heart of an undead star.

Allow me to elaborate:

In the beginning, there were hydrogen and helium. The primordial fires of the Big Bang produced almost exclusively the two lightest elements, along with a minuscule trace of lithium. It was a start, but that's not much to build a universe out of. Fortunately, the universe is full of element factories. We call them "stars".

Stars are powered by nuclear fusion, smooshing light elements together to make heavier elements, and releasing tremendous amounts of energy in the process, powering the star and making it shine. This goes on for millions to billions of years depending on the stars mass (although not how you might think, the bigger stars die young), the vast majority of that time spent fusing hydrogen into yet more helium. Eventually, the hydrogen in the core starts to run low, and if the star is massive enough it starts to fuse helium into carbon, then oxygen, neon, and so on up through successively heavier elements.

There's a limit to this though:

This chart shows how much energy is released if you were to create a given element/isotope out of the raw protons and neutrons that make it up, the Nuclear Binding Energy. Like in everyday life, rolling downhill on this chart releases energy. So, starting from hydrogen on the far left you can rapidly drop down to helium-4 releasing a ton of energy, and then from there to carbon-12 releasing a fair bit more.

But, at the bottom of this curve is iron-56, the most stable isotope. This is the most efficient way to pack protons and neutrons together, and forming it releases some energy. But once its formed, that's it. You're done. Its already the most stable, you can't get any more energy out of it, and in fact if you want to do anything to it and make it into a different element you're going to have to put energy in.

So, when a massive star's core starts to fill up with iron, the star is doomed. Iron is like ash from the nuclear fire that powers stars, its what's leftover when all the fuel is used up. When this happens, the core of the star isn't producing energy and can't support itself anymore and catastrophically collapses, triggering a supernova explosion which heralds the death of the star.

What kind of stellar-corpse gets left behind depends again on how massive the star is. If its really big, more than ~30 times the mass of the sun and its probably going to form a black hole and whatever was in there is gone for good. But if the star is a bit less massive, between 8-25 solar masses, it leaves behind a marginally less-destroyed corpse.

The immense weight of the outer layers of the star falling down on the core compresses the electrons of the atoms into their nuclei, resulting in them reacting with protons and turning them all into neutrons, which creates a big ball of almost pure neutrons a couple miles across, but containing the entire mass of the star's core, 3-5 sun's worth.

This is the undead heart of the former star: a neutron star.

If, like many stars, this one wasn't alone but had a sibling, it can end up with two neuron stars orbiting each other, like a pair of zombies acting out their former lives. If they get close enough together, their intense gravity warps the fabric of spacetime as they orbit, radiating away their orbital energy as gravitational waves, slowing them down and bringing them closer together until they eventually collide.

The resulting kilonova explosion destroys both of the neutron stars, most likely rendering the majority of what's left into a black hole, but not before throwing out a massive cloud of neutron-rich shrapnel. This elder-god blood-splatter from the collision of the undead hearts of former stars contains massive nuclei with hundreds to thousands of neutrons, the vast majority of which are heinously unstable and decay away in milliseconds or less. Most of their decay products are also unstable and decay quickly as well, eventually falling apart into small enough clusters to be stable and drift off into the universe becoming part of the cosmic dust between the stars.

However,

Some of the resulting massive elements are merely almost stable. They would like to decay, but for quantum-physics reasons decaying is hard and slow for them, so they stick around much longer than you might expect. Uranium is one such element, with U-238 having a half-life of around 4.5 billion years, about the same as the age of the Earth, and its spicier cousin U-235 which still has a respectable 200 million year half life.

These almost-stable isotopes were only able to be created in the fiery excess of energy in a neutron star collision, and are the only ones that stick around long enough to carry a fraction of that energy to the era where hairless apes could figure out that a particular black rock made of them was emitting some kind of invisible energy.

So as I said at the beginning, Uranium is significant because it stores the fossilized energy of the destroyed heart of an undead star, and we can release that energy at will if we set it up just right.

When you say it like that, is it any shock that the energy in question will melt your face off and rot your bones from the inside if you stay near it too long?

[kakita-shisumo]

Somebody mentioned the "we are all made of stardust" thing today and it reminded me how much that idea frustrates me. Not because it's wrong, per se, but because it's too simple. It misses out on some of the most important parts of the reality of how our constituent elements got here.

Calling us "stardust" massively understates our connections to the deepest parts of space and time. We're the children of some of the most violent events to ever happen in the universe.

The carbon that makes up every kind of life we know only exists when the heat at a star's core reaches temperatures six times hotter than the core of the Sun, and it is hurled out into the universe from the atmospheres of stars that are heaving their dying breaths.

The iron in our blood comes from a fusion reaction that only triggers when a supermassive star collapses inward, rebounding off of its own core and sending a shockwave slamming into the collapsing outer shell of its atmosphere that sears silicon atoms into radioactive nickel isotopes, burning as much as half the star's remaining mass in the space of a single day. Any elements more massive than iron are born within a single second of that process, in the heart of a supernova explosion, or in the cataclysmic impact of two neutron stars colliding, something that creates echoes in the fabric of space itself that can be heard on the other side of reality.

We are not just stardust. We are phoenixes, born from the ashes of cosmic annihilation. Spacetime carries our birth cries. Our progenitors were blue giants, supernovae, black holes. Stellar systems evaporated to herald our coming. We are what remains on the other side of entropy.

We are celestial fire. Never stop burning.

[kissandkeepbusy]

we are all star stuff.

[transgenderenkidu]

that's a heavy burden, son of the sword

i think sometimes about how the heaviest element a star can synthesize without going supernova is iron, and how when a star's core reaches iron it cant burn any longer

anyway take this intensely self indulgent chapter 18 fanart, kendal is from @comicaurora, the only thing ive read that consistently inspires me to draw full color pieces

[raphohwell]

Okay so nuclear fusion. To be able to ramble at my leisure, I’ll assume you don’t know that much about it.

Contrary to nuclear fission, in which strong pressure and heat is used to separate fissionable atoms using a neutron, nuclear fusion uses pressure and heat to fuse two lighter atoms into a heavier one, subsequently emitting neutrons. This is achieved by pushing the two atoms trough a barrier, which is INCREDIBLY difficult to achieve.

The Sun itself is the primary exemple of nuclear fusion. In it’s core, helium atoms are fused into hydrogen atoms under cataclysmic levels of heat and pressure.

To be clear, this particular reaction is not unique. Different stars types create different elements during different reactions. Over the course of a star’s lifespan, the type of reaction that happens will change from fusing lighter elements to fusing heavier elements.

Now to introduce quantum mechanics into it because we are masochists and a bit crazy.

Quantum mechanics is the study of the nature of things at or below the scale of atoms. The mechanic we are interested in today are quantum wave theory, wave particle duality and quantum probability.

Quantum mechanics can describe things that classical physics cannot. Classical physics can describe many aspects of nature at an ordinary scale, but is not sufficient to describe them at very small scales.

For example; to describe the characteristics of a ball pitched in a baseball match, classical physics are enough. You can calculate the wind speed, atmospheric pressure, temperature, forces on the ball, etc. to get an idea of where that ball will land.

You would use quantum physics to understand where and how a given particle of a very small scale will behave. Using many different mechanics and behavioural patterns, you can set probabilities for how a given particle will engage with its environment.

A basic thing to remember is that following quantum physics, you have what is called the uncertainty principle. In layman’s terms, it simply refers to the fact that no matter how a quantum particle is prepared or how careful we are with experiments, it is impossible to have a precise prediction for a measurement of its position and also at the same time for a measurement of its momentum. In other words, the nature of quantum mathematics is that measuring more things will result in more probabilities and less certainty.

This makes reference to the fact that an object can be both a wave and a particle, or at least exhibit characteristics of both. Classical physics often fail to describe the nature of quantum objects using the concepts of wave or particle.

ALL THIS TO SAY. Quantum physics are less scary than they seem (not really).

Now, you might wonder, but Raph, how does this all fit together? The answer is quite simple; Classical physics cannot explain nuclear fusion, because according to all known laws of physics (hehe), the sun should not be able to produce a fusion reaction with it’s internal pressure and heat.

It takes a special phenomenon, referred to as quantum tunnelling, to ensure nuclear fusion is possible under expected conditions. After all, the sun is very much supporting nuclear fusion, so there must be something we can use to explain it. (Lot’s of quantum physics is like this btw)

Quantum tunnelling is a phenomenon in which an object passes trough a barrier trough which it should not be able to pass, lacking sufficient energy to do so. The smaller the barrier, the higher the probability of an atom or subatomic particle passing trough is.

To understand the phenomenon, particles attempting to travel across a potential barrier can be compared to a ball trying to roll over a hill. Quantum mechanics and classical mechanics differ in their treatment of this scenario.

Classical mechanics predicts that particles that do not have enough energy to surmount a barrier cannot reach the other side. Thus, a ball without sufficient energy to go over the hill would roll back down. In quantum mechanics, a particle can, with a small probability, tunnel to the other side, thus crossing the barrier. The reason for this difference comes from treating matter as having properties of waves and particles.

Imagine, if you will, a sound wave, crashing into a wall. Now my high school physics have been gone for a while, but if I remember correctly, the wave crashes into the wall, is redirected, but by vibrating the wall, it goes trough the other side. Simple as that. Quantum tunnelling is just the nerdier, more complicated, headache inducing version of that.

At least be thankful I spared you the unending mathematical equations. I wasn’t spared and I DO have a headache now.

Still following? I’m not. I’m super confused right now. Rewrote this three times already. Had to occasionally go read Wikipedia articles to make sure not to bullshit you.

Blah blah, Schrödinger’s Cat, Chekov’s Gun, Schrödinger’s Gun, Chekov’s Cat… where was I?

Yes, here. Joining together everything, quantum tunnelling is an essential phenomenon for nuclear fusion. The temperature in stars is generally insufficient to allow atoms to overcome the barrier and achieve nuclear fusion. Quantum tunnelling increases the probability of penetrating this barrier. Though this probability is still low, the extremely large number of atoms in a star is sufficient to sustain a steady fusion reaction.

Holy fuck this took a while. I tried my goddamn best to make it palatable and funny but it still reads like a chore so I’m not sure of the result. I’m not sure of your theoretical level so that was also a challenge because I had to constantly imagine myself trying to explain this stuff to my mom so I wouldn’t use technical jargon and complex equations.

I NEED YOU TO TELL ME IF YOU DIDNT GET SOMETHING THIS IS A TEST IN MY TEACHING ABILITIES.

also if anything is wrong please i beg of you tell me

Also I’m going to sleep now so I’ll probably only see your answer tmr.

is somebody gonna match my freak??

( talk about the universe for hours and eat with me at a dessert buffet )

[spacenutspod]

Water is the most common chemical molecule found throughout the entire universe. What water has going for it is that its constituents, hydrogen and oxygen, are also ridiculously common, and those two elements really enjoying bonding with each other. Oxygen has two open slots in its outmost electron orbital shell, making it very eager to find new friends, and each hydrogen comes with one spare electron, so the triple-bonding is a cinch. Hydrogen comes to us from the big bang itself, making it by both mass and number the #1 element in the cosmos. Seriously, the stuff is everywhere. About 75% of every star, every interstellar gas cloud, and every wandering bit of intergalactic space debris never to know the warmth of stellar fusion in 13.8 billion years of cosmic history is made of hydrogen. That hydrogen got its start when our universe was only about ten minutes old, and all the hydrogen that has ever existed (except for random radioactive decays and fission reactions, but that would come later) formed before our universe turned 20 minutes. A dozen minutes, 13.8 billion years ago. When you quench your thirst with a healthy glass, that’s what you’re consuming. We can understand this epoch of cosmic history, known as the nucleosynthesis era, because over the past century we’ve become rather skilled at dealing with nuclear reactions, and in one of the hallmarks of our species we have unleashed this radical understanding into the physical nature of reality and deployed it for both peacetime energy generation and wartime bombs. Our understanding of nuclear physics tells us that earlier than the ten-minute mark, our universe was too hot and too dense for protons and neutrons to form. Instead their subatomic parts, known as quarks, were unglued in a heaving maelstrom of nuclear forces, constantly binding and unbinding in a seething rage-filled sea of gluons, the force carriers of the strong nuclear force. Once the universe expanded and cooled enough, condensates of protons and neutrons formed like droplets on the windowpane, low-energy pockets capable of keeping themselves together despite the temperatures. Eventually, however, as soon as the party got going it fizzled out: when the universe became too large and too cool, a mere dozen minutes later, there wasn’t sufficient density to bring the quarks close enough together to perform their nuclear binding trick. Some protons and neutrons would find each other in those storm-filled days, though, forming heavier versions of hydrogen, some helium, and a small amount of lithium. And since then those hydrogen atoms have wandered about the cosmos; most lost in the intergalactic wastes, some participating in the glorious construction of stars and planets, and a lucky few finding themselves locked in a chemical dance with oxygen. The oxygen has another tale to tell, also a story of fusion, on its way to becoming water. But not the fusion of the first few heady minutes of the big bang, but in the dance within the hearts of stars. There, crushing pressures and violent temperatures slam hydrogen atoms together, forcing them to fuse into helium, in the process releasing an almost vanishingly small amount of energy. But that forced marriage happens millions of times every second, in every one of the trillions upon untold trillions of stars strewn about the cosmos, enough to light up the universe for all conscious observers to enjoy. Near the end of a star’s life, it turns to fusing the built-up ash of helium piled in its core, The fusion of helium produces two products: carbon and oxygen. Now this oxygen would end up forever closed off from the cosmos, locked behind a million-kilometer thick wall of plasma, if it were not for a trick of physics that happens when the star meets its final days. Our Sun will someday experience this fate, about four and a half billion years now. When it grows old and weary, it will swell and turn red, violently spasming as it draws its last fatal breaths. Those gargantuan shudders release material from the star, launching it into the surrounding system, billowed by gusty winds of fundamental particles streaming away at nearly the speed of light. Fit by ragged fit, the Sun will lose its own self, driving away over half its mass into a spreading nebula, the only sign that distant eyes can perceive of yet another noble star laying down its struggle against the all-consuming night. But in that gruesome death, a miracle. The cycle born anew: the hydrogen and helium, the primordial elements of the star, now mixed with carbon and oxygen drift off into the interstellar void, someday to take part in the formation of a new star, a new solar system, a new world wet with water, and, if the chances are perfect, a new life. The post Thirsty? Water is More Common than you Think appeared first on Universe Today.

[gent-illmatic]

Yes, in a sense, the human body and all life on Earth are composed of elements that originated in stars. This concept comes from the field of astrophysics and cosmology:

Stellar Nucleosynthesis: Elements like carbon, oxygen, and iron, which are essential to life, are formed in the cores of stars through nuclear fusion.

Supernovae: When massive stars explode as supernovae, they release these elements into space.

Solar System Formation: Our solar system, including Earth, formed from a cloud of gas and dust that contained these stellar elements.

Biological Composition: The elements that make up the human body, such as carbon, hydrogen, oxygen, and nitrogen, were originally created in stars.

So, while the term "stardust" is poetic, it accurately reflects the scientific understanding that the materials in our bodies have their origins in the stars.

In a poetic sense, you could say that we are "stars in the flesh" because the elements that make up our bodies originated from stars. This phrase captures the idea that our physical existence is connected to the broader cosmos through the process of stellar nucleosynthesis and the recycling of cosmic materials. Scientifically, it highlights our deep connection to the universe and the remarkable journey of the elements that constitute life on Earth.

[spacetimewithstuartgary]

Simulations with new k−ω model offer insights into massive star convection processes

Researchers at Yunnan Observatories of the Chinese Academy of Sciences simulated the evolution of massive stars with masses ranging from 50 to 150 solar masses during the nitrogen sequence Wolf-Rayet (WNL) star phase.

They employed a newly developed k−ω model to handle the convective overshooting processes within the stellar interior, offering a more precise understanding of this complex phenomenon in massive stars.

This study was published in The Astrophysical Journal.

At the boundary between the convective and radiative zones of stars, fluid retains inertia and overshoots the convective zone, thereby bringing elements from the convective zone into the radiative zone.

WNL stars typically form during core hydrogen burning, with their surfaces becoming enriched in nitrogen due to strong winds that strip away their outer envelopes.

The processes of convection and overshooting transport nucleosynthesis products to the outer layers, resulting in anomalous surface enrichment and altering the stars' evolutionary paths. Therefore, studying WNL stars provides insights into the effects of convection and mass loss on stellar evolution.

The researchers compared the results from the k−ω model with those from the previously used exponential decay model for handling the overshooting zone.

They found that the k−ω model predicted a broader range of mass and lifetime evolution for WNL stars under the same initial conditions, such as mass and metallicity. Additionally, it lowered the model limit for WNL star formation, which was attributed to the k−ω model's ability to expand the mixing zone of materials within the star.

Furthermore, the researchers considered the factor of rotation and found that rotation may play a crucial role in the formation of lower-mass and metal-poor WNL stars. This effect was more pronounced in the previous model.

By utilizing a new model for convective overshooting, this study provides fresh perspectives and more accurate results in revealing the evolutionary patterns of special stellar phases like the WNL stages.

Moreover, the differences in outcomes between the two convective overshooting models offer the researchers alternative options for inferring the initial evolutionary environments and distributions of observed samples.

 The H-R diagram shows the evolutionary tracks of stars across various metallicities, encompassing initial masses from 50 M⊙ to 150 M⊙ in increments of ΔM = 20 M⊙. Credit: The Astrophysical Journal (2024). DOI: 10.3847/1538-4357/ad6b13

[uncontrolledfission]

What is a neutron star merger?

Post #4 on Physics and Astronomy, 08/07/23

I'm not sure where, but somewhere a certain phrase was imprinted into my head. I genuinely have no idea where I got it from, so in this post and the next I'll be exploring that very phrase: 'nucleosynthesis in merging neutron stars.' I genuinely have no idea where it came from. Goodness, I really was born to be a physicist.

Neutron stars are what's left of a star at the end of its life cycle. They're the alternative to becoming a black hole. Neutron stars are one of the universe's most dense stellar objects, save from whatever it is that exists at the heart of the black hole. For reference, they're estimated to pack the mass of the Sun into the size of a city. Wild, right?

Since these neutron stars are packed so tightly, the boundaries of these atoms' nuclei actually disappear. Einstein's theory of general relativity then means that these stars emit gravitational radiation: 'ripples in the geometry of space and time.' (Caltech.) This causes the orbits of those stars to shrink and and gradually bring them closer together. This is no hurried process--it can take place over millions or billions of years.

Just so you can visualise (if you can visualise) it, this process can take place over 1 billion years, eventually climaxing at 1,000 spins per second, followed by the actual merge of the stars in the matter of a few milliseconds. The merger releases a burst of gravitational waves and gamma radiation in the process. Of course, not all neutron star mergers will follow this model, but it's fun to imagine. You can watch a simulation of sorts here.

This merger can lead to the formation of a larger black hole, or just a larger neutron star--which of these outcomes occurs depends on whether or not the Tolman-Oppenheimer-Volkoff limit is exceeded by what's left. This limit, which I'll abbreviate to the TOV limit (NOT to be mistaken with Treaty of Versailles!!) refers to the maximum mass of a neutron star. Current values for this limit are approximately 2.1 solar masses (1 solar mass is around 2 x 10³⁰ kilograms).

This then begs the topic of nucleosynthesis in these merging neutron stars. But that process is so fascinating, I think it deserves an article of its own.

UP NEXT: Nucleosynthesis in neutron star mergers.

Sources:

Gravitational radiation.

General relativity.

Neutron star collision. NASA.

Not a source but something I read as I was writing this: is the boundary of an atom well-defined?

The Tolman-Oppenheimer-Volkoff limit.

Neutron star merger. NASA.

[ghelgheli]

A month ago, NASA released a new image of the supernova remnant Cassiopeia A taken by Webb's near-infrared camera (left). This reveals a more subdued object than an earlier mid-infrared image (right), but both are available in very high resolution revealing structural details.

Cassiopeia A is the youngest supernova remnant in our galaxy, making it an object of intensive study; its progenitor star is estimated to have exploded 340 or so years ago. Supernovae are the strongest known explosions in the universe, and any localized in the Milky Way are likely to be visible to the naked eye, even in daylight. But there is only tenuous evidence of Cassiopeia A entering the historical record at birth.

The remnant has expanded to a size of around 20 light years in the mere three centuries since, reflecting the speeds achieved by matter ejected in a supernova. Even the smallest details visible in the near-infrared image span a hundred astronomical units—twice the distance between the Sun and Pluto when the two are furthest apart. The remnant continues to expand at up to five percent the speed of light.

Long-term study of supernova remnants like this one are often interested in the profile of heavy elements they disperse. Note that astronomically, anything heavier than helium is a "metal", a distinction made to signify the fact that these elements can only be produced in later stages of stellar nucleosynthesis. The truism that "we're made of stardust" often refers to this process and the subsequence dispersal effected by a supernova.

[niobiumao3]

Oh Baylan

So the more I think about it the more I suspect naming Shin and Baylan for Skoll and Hati is not just an affectation.

Skoll and Hati chase the sun and the moon across the sky in Norse Mythology. When they reach them and devour them Ragnarok will begin and the world will end, ushering in the next world.

Baylan says a few key things about creation needing to come after destruction (a bit of stellar nucleosynthesis there to go with his name), and he also 1) blames Ahsoka for Anakin's fall vis a vis her 'abandoning' him, 2) talks about Anakin's legacy being one of death.

So, he's well aware Thrawn's going to start a war, and plainly doesn't care, but he's also not terribly invested in Thrawn or Morgan's designs. Why would that be?

My suspicion stands: he wants the temple remains on Thrawn's ship to get into the World Between Worlds so he can kill Hitler Palpatine.

I actually don't think it's Anakin he intends to kill. My reasoning here is based on the fact that by now everyone knows the Emperor was The Real Problem and Vader was just his instrument. More-over, if Baylan did think Anakin was the root issue I don't think he'd have chatted with Ahsoka the way he did.

This leads me to two things:

It's clear Filoni thinks Anakin was inherently bad, i.e. he was always going to Fall, which is what Ahsoka is no doubt going to discover, so it won't matter if Baylan DOES kill Palpatine

Even if we assume the above weren't true he'd need to kill Palpatine back when he became a Chancellor--and all that does is free up Dooku to do what he wants, and I bet that still means corrupting Anakin.

Anyways, we'll see if I'm right (I'm usually not lol) but I feel a lot of Baylan's revealed motivations and behaviors suggest he feels okay with promising people stuff because he's just going to unmake reality anyways. Sure, Sabine! You can go see Ezra. I'm going to get rid of this timeline anyways. :)

[fimproda]

Habemus titles - Gwynriel + Elucien fanfiction

(Or, I found yet another way to flex my knowledge of Latin and chemistry)

I literally have a biochem PowerPoint doc open on my laptop as I write this. I should be studying. I couldn't care less.

As most of us writers know and experience, long showers are an endless source of inspiration.

I washed my hair yesterday. It was... productive.

So, without further ado:

Gwynriel: Nucleosynthesis

Stellar nucleosynthesis is the process by which elements are created in the nucleus of a star. I learned this in my Inorganic Chemistry 2 course last year, and I've been thinking about it ever since.

The title fits pretty nicely in the "space" theme of the Under the Stars series, and it's also indicative of the STEM-ish plot lines and worldbuilding that I decided to give this story and the Dawn Court as a whole.

Just to drive this point home, the chapter titles will be named after the elements that can be produced in the core of a star—that is, all the elements up to nickel except for hydrogen, which is the starting material.

(If you really want to know, heavier elements can only be produced by the explosion of a supernova.)

I've been literally patting my back for more than half a day at this point. I'm so proud of this title.

Elucien: Sol niger

Sol niger means "black sun" and refers to nigredo, the first stage of the alchemical magnum opus. The chapter titles will have something to do with the sun, as well; I'm thinking of naming them something like Flare, Corona, Eclipse, etc.

I'm sure you can understand the reason behind the "sun" part of this title, but why does this sun need to be black, of all colors?

Nigredo, as the first step towards obtaining the philosopher's stone, is the stage in which all alchemical elements need to be "cooked" together to achieve decomposition and putrefaction. It's a rotten, messy thing, then, but one which ultimately leads to perfection and success.

Remember what I said in my latest post about this story? Among other things, I told you that there would be a third POV, and that I may or may not kill Beron off.

Well, I can now tell you that the third POV is

drum roll

Eris, and all this "black" stuff refers to him and his crusade against his cruel father.

Some real swell stuff, as you can see.

But on the flip side, his hounds will make more than one appearance! So at least I can say that there are some happy things in this plot line, as well.

Reblog and hit like for Eris's doggies 🐶

[lifblogs]

Researching stellar nucleosynthesis for part 2, chapter 2.

[etirabys]

Enormous aliens whose cells perform stellar nucleosynthesis scooping galaxies into Petri Spheres and saying "there are so many microorganisms, spread out so thinly, we'll never understand it all, but we can learn SOME underlying princi... oh, look at the radio bloom in this corner!"

"Hey, wasn't there a bunch of oxygen signature from that corner just ten megayears ago? There was a mass deoxygenation event, THAT's interesting, get me a femtoscope..."

[sakuraswordly]

@ExploreCosmos_: Rigel is the brightest star in the constellation of Orion and the seventh brightest star in the night sky. Its name originates from the Arabic word for "foot" or "leg," reflecting its position as the foot of Orion, the mighty hunter of Greek mythology. 2/ With a visual magnitude of about 0.13, Rigel shines fiercely, illuminating its surrounding cosmic neighborhood. Rigel belongs to the spectral class B8Ia, indicating that it is a massive, luminous star with a surface temperature of approximately 11,000 Kelvin. 3/It is estimated to be around 21 times the mass of the Sun and roughly 78 times its radius. Such immense proportions classify Rigel as a blue supergiant. Rigel's luminosity is staggering, with a brightness approximately 120,000 times that of the Sun. 4/Being a blue supergiant, Rigel burns through its nuclear fuel at a rapid pace. As a result, it has a relatively short lifespan compared to smaller, less luminous stars. Estimates suggest that Rigel is only a few million years old & is already nearing the end of its life cycle. 5/ Rigel does not exist in isolation; it is part of a larger stellar system that adds complexity and intrigue to its celestial narrative. Rigel has a companion star, Rigel B, which is often overlooked due to the brilliance of its primary counterpart. 6/Rigel B is itself a spectroscopic binary system, consisting of two stars orbiting around a common center of mass. These stars are likely smaller and less massive than Rigel A, contributing to the overall dynamics of the system. 7/ While no confirmed exoplanets have been discovered in the immediate vicinity of Rigel, astronomers continue to investigate the possibility of planetary companions around this massive star. The intense radiation and stellar winds emitted by Rigel pose challenges for the ... 8/ formation and stability of planetary systems. However, theoretical models suggest that distant gas giants or rocky worlds may orbit within the habitable zone of Rigel, albeit under extreme conditions. 9/Rigel's radiance also illuminates the surrounding interstellar medium, shaping intricate structures such as the Witch Head Nebula. This nebula, located approximately 900 light-years away, reflects the intense ultraviolet radiation emitted by Rigel, creating a ... 10/ stunning cosmic vista for observers on Earth. Rigel's prominence extends beyond its celestial beauty; it serves as a crucial object of study for astronomers seeking to unravel the mysteries of stellar evolution, nucleosynthesis, and the dynamics of stellar systems. 11/ As a blue supergiant approaching the later stages of its life, Rigel offers valuable insights into the fate of massive stars. Scientists observe its behavior to understand processes such as core fusion, mass loss, and eventual supernova explosions, ... 12/which enrich the cosmos with heavy elements essential for the formation of new stars & planetary systems. We employ a variety of observational techniques, including spectroscopy & photometry, to analyze Rigel's spectrum, luminosity variations & physical properties. These observations deepen our understanding of stellar atmospheres, interior structure, and evolutionary pathways, contributing to broader theories of stellar evolution and galactic dynamics. 14/ With advancements in astronomical instrumentation and space exploration technology, researchers anticipate further discoveries and insights into the Rigel system. Future missions may include detailed spectroscopic studies, direct imaging of potential exoplanets, ... 15/and enhanced simulations to model the complex interactions within this dynamic stellar environment. Rigel stands as a beacon of cosmic wonder, captivating observers with its brilliance and scientific significance.

[tofupunx]

Something we've all heard is that we are "made of star dust" - which is true, but I think it might be cool to see someone talk about what that really means in a Tumblr rant.

Would you have any interest in infodumping about stellar nucleosynthesis, the different classes of stars and their limits of element production, and how we get the naturally occuring elements heavier than iron and nickel?

Yes I absolutely would! I have tried to make this as coherent as possible, but I’m a rambler and I like talking about stars!

So the statement that we’re all star dust is factually correct - I love to remind people that we all came from violent explosions and reactions in the cosmos, and we will all return to that one day too. Very comforting.

So “nucleosynthesis” refers to the creation of atomic nuclei from less complex nucleons, such as hydrogen-1 (literally just a single proton). It started with primordial nucleosynthesis, also known as “Big Bang” nucleosynthesis. This, obviously, happened very early on in the Universe, as in literally minutes after the Big Bang [is theorised to have] happened. Basically, just like in the cores of stars, stuff was really hot and dense. And so from the plasma came neutrons and protons. The hot, dense conditions allowed for your boy Hydrogen-1 to fuse to form heavier elements, such as deuterium (“heavy” hydrogen), helium and lithium. Then everything started to chill out a bit, literally.

Stellar nucleosynthesis is an important part of the evolution of stars. Stars are formed when clouds of gas and dust collapse in on themselves due to their own gravity, becoming very hot and dense in the very centre of what will soon be called a “protostar”.

Now, not all stars are created equal. For those protostars that are pretty small, with a mass typically less than 0.1 times that of our Sun (this is known as solar mass, with 1 solar mass = the mass of our Sun), no nuclear fusion happens in their cores because they are simply not hot enough (although some are able to fuse deuterium and even lithium). These types of stars are known as brown dwarfs.

The next class of star are stellar-mass main sequence stars. As you can probably guess, our Sun is a perfect example of one of these bad boys. They’re pretty average, and relatively common in the Universe. These stars are massive enough to allow for P-P chain (proton-proton chain) reactions, fusing hydrogen into deuterium and helium. For stars on the slightly larger side of this, the CNO cycle can take place (carbon-nitrogen-oxygen cycle). The CNO cycle uses particles such as (surprise surprise) carbon, nitrogen and oxygen as catalysts for nuclear fusion, and in turn releases an enormous amount of energy, usually in the form of gamma rays.

“Main sequence” refers to any star in its prime, where it reaches a state of hydrostatic equilibrium - i.e. the outwards force from the reactions in the core balance out with the inwards gravitational force and keep the star from collapsing. The hotter and more dense a star, the heavier elements can be produced by the nuclear fusion in its core. As temperatures and pressures rise, more complex reactions such as the triple-alpha process (to create carbon from helium) and the alpha process (to create heavier elements from helium) can occur.

Stars around 8 solar masses or more can burn carbon, neon, oxygen and silicon. In short, the more massive the star, the more hot and dense it is, which means it can burn and fuse heavier and heavier elements. That is, as you’ve mentioned, until iron. Iron is an incredibly stable atom, which is why stars have difficulty producing anything heavier or more complex.

So, stars on the main sequence will eventually run out of hydrogen fuel, and this means they won’t be able to balance the inwards force of gravity anymore. Stars of different masses will react to this situation differently, with more massive stars ending their main sequence lifetime with violent supernovae, and low-mass stars gradually fading. Stars like our Sun will eventually collapse and cool, leaving just the dense core known as a white dwarf.

For heavier elements to form, there needs to be suitable conditions for neutron and/or proton capture. There are several methods of these: rapid neutron capture (r-process), slow neutron capture (s-process), proton capture (p-process), and rapid proton capture (rp-process). Saving the details, these processes are pretty mental. A massive star collapsing into supernova provides the conditions for these reactions to occur, and thus for elements heavier than iron to form and be scattered throughout the Universe, potentially going on to form more stars, planets or nebulae. The remnants of these massive stars will become neutron stars or even black holes, but that’s a whole other story.

TLDR: dying stars make heavy shit.