YouSaid · the spoken record

Anna Frebel

lines on the record: 167
first: 2023-05-18
most recent: 2023-05-18
sittings or episodes: 1
sources: podcast

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“Um, that's a good question. I mean, you know, it starts with mundane things as in you won your telescope time, you travel there, and the weather is completely cloudy, it rains, and you had three nights, which is a lot, and you go home empty-handed. So that's definitely a low point Probably not what you were thinking of, but there is a certain occupational hazard to it.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“White dwarfs have lost all their outer atmosphere. So it's just the hydrogen helium core. So they look like a metal poor star because that's only hydrogen helium left, right? But the hydrogen ions that you can see in the spectrum of R stars and of the white dwarfs are a little bit wider than normal. So you need to have a good eye just to check, does this look a little bit wider than us? Is this a white dwarf who's fooling me here, right? And so it's like this moment. It's like, oh my God. It's just.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“That was definitely one of those moments I wasn't actually present at the telescope, but we were sent the data immediately from our colleague. And we just looked at it and our eyes got really white and was like, oh my God, this is really what you think it is. So we had to run some numbers and it was. And these are magical little moments. The thing is. Know often we have false positives. And so there's always this kind of period, and often it's, I don't know, 10, 15 minutes where you need to make some tests to kind of make the decision. Is this really something I should keep observing now? Is this really as good as I think? Or am I being fooled by something, right? So actually, if you take a spectrum of a white dwarf, a white dwarf is the leftover core of a star like the sun that has gone extinct.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“But we'd really like a measurement. So we are looking for the last little bit that you could possibly detect. And that's the strong function of the brightness of the star because the telescopes have the size that they do, that that's not going to change for a while. Hopefully eventually it will, but it's going to be at least 10 years out. And so, yes, we're often literally stuck in the noise because we can't make the measurements. So actually the record holder for the most iron poster only has an upper limit. We can't get enough data on this to actually pinpoint a measurement to then take it to our theory colleagues and say like, give me this little iron out of your first star. So it's a bit frustrating, but also super exciting at the same time.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“So, the most iron postas, their iron lines are so tiny. To make detections And the funny thing is, we're looking for the nothingness of, let's say, the iron lines, but then we don't want nothing because if there's nothing in the spectrum, we can't measure anything. We can only get an upper limit.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Well, that's literally what we're doing in multiple ways, actually. So we're trying to find the needle in the haystack. And then we find something. And then it turns out it's just a little bit too faint to actually get the kind of data quality on it that we would like or that would be warranted given the potential of the star, right? Was like”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“That's right because these stars are a little bit like the needle in the haystack, right? They're not that many left over. And certainly the galaxy has made plenty of stars in between. We need to comb through all of those. To get to the goods. So, we always start with millions and then work our way down. And in the end, we have like three good candidates.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Very narrow filters. So it's like you're wearing very specific glasses that only lets so much light through. And so we can do similar things through having several narrow band filters, what we call it, to fish out things that have no absorption over here. So just the straight line and then a little dip here, so a little something there. And that has proven fairly successful in recent years.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“And people had been trying to study those, and they had taken little spectra of all things in the sky. And it turns out, oh, you can fish out the actual stars from that and look for certain signatures that might indicate low metallicity stars or stars with low abundances. And so it was painstaking work to then take medium resolution spectroscopy to get a little bit more information and to use approximations and to kind of get candidates that we can then eventually take to the big glass like Magellan to get a high resolution spectrum. So we really see the dips of all the individual elements that then give us a final answer. Is it yay or nay? These days with another grad student, I developed a new technique to use images actually of all the stars in the sky taken with”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, yes, yes. So to cut a long story short about the searching, we started early on with what's called low resolution spectroscopy of many stars. So for example, my thesis work almost 20 years ago was piggybacking of a quasa survey that had collected, so quasars are basically giant supermassive black holes that are really far away. So you only see one big bright light point. So it looks like a star, but it's actually just a giant supermassive black hole that outshines its own galaxy.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, but it kind of remains really hard. But the thing is that past three, many of us are, okay, we solved that problem. We've done it three times. We can do it. That's a thing, right? That's a population, three iron deficient stars, let's say, right? That's one puzzle piece. Now we can move on to the next thing.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, yes. We have the saying I learned this, I think, from my supervisor. One star is a discovery. Two is a sample and three is a population. So as soon as you found three of roughly the same kind, you're done. But you need to get there.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“It's not random. There's a lot of work that goes into that. I began my career by trying to answer that question as in like doing the search process. That's why I called my book that I've written some time ago, Searching for the Oldest Stars, because searching is one thing. It's very time consuming. And then on top of that, not everyone finds, right? And I often don't find, but I keep searching because, you know, techniques have established that, yes, we can do it if we're just patient enough and keep going because it's a numbers game. And that's often the case in science. And that's something that not enough is talked about, how tedious it is and how long it takes to get to that one. Discovery, right? That moves the field further.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Exactly. And so that's a thumbs up, thumbs down. Are you worth my time or not? In most cases, it's not or it's good enough. We can do a basic analysis, maybe publish this as part of a larger sample, just so we output that we have observed the star and their basic nature, that that's an important part to publish as well. And yeah, I had a run. So now we do remote observing. I do all of this now from my home from my living room all night long. And I often work with colleagues. So we do it over Zoom and we process the data. We look at it. Same thing still. And we just found a star that had a very low iron abundance. And then we decided, okay, that looks interesting. We're just going to keep exposing. So we took more data on it on the spot. And we're writing up the paper right now.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“We actually process our, it's fairly straightforward to do our processing. We do it at the telescope. So I often take a shorter exposure first, let's say 10 or 15 minutes. So mostly when I do discovery work, we would just take a quick look spectrum, then reprocess it while we observe the next, then we take a quick look. We have what I call the summary plot. It's a collection of little areas in the spectrum that have the key positions, the positions of the key elements in it. And it's kind of like reading the tea leaves. I have stared at so many spectra. I just need to know our summary plot and I can tell you exactly what the numbers are going to be.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“But the old stars have so little of all the elements that there are only occasionally these dips that then indicate, okay, that one at that wavelength was iron and here we have carbon and there's magnesium and sodium. Oh, there's a little strontium line here. So we have a much easier way to map out this barcode that the spectrum pretty much is at the end of the day and to then measure the strength of these we call it absorption lines to then calculate with existing codes that mimic the physics of the stellar atmospheres, like how much was absorbed, how many, what kind of elements were present in the stellar atmosphere. And so this is how we get to our abundance measurements and then all together that gives us the chemical composition and that particular signature in that star.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“And so that means that if you are the observer with a spectrograph or without, you will see the starlight, but certain frequencies, certain energies of that light will have been absorbed by all the different atoms in the gas. So you see less of them. And so those are the dips. And the strength of the dips tell us which element was it and how much of that element was or is in the star. So we have many, many, many dips. The solar spectrum for reference, you know, all the dips are overlapping because the abundance of all the elements is so high. It's actually very complicated spectrum. My spectral, I really look like a straight line. And then there's a dip here and then the straight line again is a dip there. The sun doesn't have straight lines. I mean, that's just all absorbed in some form or another.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“But it would be a rainbow with lots of black lines in it, which means certain little pieces of color have been eaten away by a certain amount. And so we can no longer see it as well or not at all. Why is that happening? So, if we come back to our stars, what we're observing, we're observing the stellar surface. We can actually never peer with our telescopes inside. We only ever can go after the surface. And the surface contains the surface layer contains different kinds of elements. Every one of those types of atoms, so elements are just different types of atoms, they absorb different photons that are coming from the hot core where the fusion is occurring.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Now, it's not going to look colorful, just black and white, different colors have, of course, different energies. That's what we record. More specifically, we record it as wavelengths, so wavelengths and frequency and energies all the same at the end of the day. We process in the sense that we do a cross-cut and then sum up a few columns so that we get all the data that we recorded. And what we see is a bit funny to describe just with words, but a wiggly line with lots of dips. So the 2D process spectrum, we call it continuum. So it's just a flat line, basically, and then there are dips. So the interesting things are the dips. If you think back of the rainbow, what we actually see in our stars is not just the rainbow.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“As a spectroscopist, we have to, I guess, talk for a brief moment about what a spectrum is. Everyone, I hope, has seen a rainbow on the sky that is That is basically what we're doing. We don't send the starlight through a raindrop that then gets bounced around and splits up the light into the rainbow colors. We do it with a spectrograph. So basically a prism. So we send the starlight through a prism of sorts. And that splits it up. And then we record exactly that. So it's a little 2D picture actually of a spectrum”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, and it's just you and nature and With modern civilization and all of that, I think we often try a little bit too hard to be removed from nature, you know, to be independent of it and figuring it all out. But at the end of the day, we're just a part of it. And that really helps me to remember that. You know, well, one and the same”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes. And just, you know, this dark sky with the bright stars. And I have described this in my book years ago. If the Milky Way is all bright above you, you don't need a moon or anything. You can walk in the starlight and you will find your way. There are no trees there for safety reasons, but you wouldn't even run into a tree, right? I mean, you can see, you can almost see the shadow, you know, from the starlight because it's such a dark sight and the stars are so bright. And these are kind of moments that kind of change you a little bit.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, yeah. It's just you can't afford to focus on just one thing. And you, it's just kind of does something to you. It's a little hard to describe. But if you then fast forward, maybe I can speak a little bit about that. I have done a lot of astrophotography there as well. And observing faint dwarf galaxy stars, you know, these are like 45 minutes, 55 minute exposures. So you actually have a lot of time. So I would run outside and just lay on the ground under the southern Milky Way. Beautiful right up, you know, there. And I would just lay there like the snow angel, you know, and just stare up there and just kind of let my thoughts sort of pass through my brain and just like I'm one of it, right? We talked about this in the beginning. This is when I personally have the feeling that I'm a part of it. I belong here rather than feeling kind.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Well, you know, when you're on top of a mountain, climbers, I guess, get to see that probably otherwise. It's very calm, and the colors are so beautiful and I always become much calmer when I'm there. I'm just A because I'm just there for one purpose only. That's data collection. I can say no to my emails. I can say no to everything else because I'm observing. So there's literally less distractions because, you know, you're just there to do one thing.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Turn this knob and see what happens. Let's turn that knob and see what happens. No, you know, we only have one experiment, which is the universe. And what we see is what we get. And I think it's so important to take an active role in that. So I really loved going to the observatory. I've taken many students there over the years to teach them and to just show them what it means to be an astronomer because you go to these remote mountaintops and it's such a magical environment and you wait there for the sun to go down and then you get ready and you look outside and it's it's such a serene environment it's a little bit out of this world”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, so it's mostly done for them. Obviously, that's super convenient, but it also takes away a central part of what the work of an astronomer is, which is data collection. Right. We don't have an experiment in the basement where we can go day and night or whenever we please and ask a certain question of the apparatus, right? Let's.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“How many photons get collected sort of per time unit? Because that's always the limiting factor. Prior to the pandemic, we would travel to Chile to do our observations. Those telescopes are the, that's the last observatory where people were sort of supposed to travel there and take their own observations. Most other observatories Basically, have staff there by now who take the observations for you.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Well, let me start by saying I mostly these days use the Magellan telescopes in Chile. They are 6.5 meter telescope, which means the mirror diameter is 6.5 meter. That's not the largest that is out there, but it's among the largest. And I use a spectrograph because I'm a spectroscopist. I don't take pictures. And that particular spectrograph at that telescope is actually unusually efficient so it kind of makes up for the fact that the mirror isn't as large in, let's say, the eight meter telescopes from the Europeans or so. So I'm very happy with that.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Would have blown apart past five supernovae or ten. So that's a really important constraint that we have that these systems are still alive, right? So it helps us to pin down where certain processes could have possibly happened. And so it's just a different type of information that we get.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“We need probably the neutron star mergers, or we need a special kind of supernova that's maybe extremely massive or heavily rotating or does something else funny, right? To really kind of get that particular process going. But the normal supernovae don't do it, right? So only a little bit comes out. But you could come alongside, Anna, why don't you just Take a hundred supernovae together to build up the yield, right? But then I come along and say, like, look, this dwarf galaxy is still intact today. If you would have plugged in 100 supernovae into this little system early on, it would have blown apart.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Probably some heavy elements come out of supernovae here and there, but somehow my theory colleagues tell me that the normal supernova just doesn't have enough oomph to really get that R process going and doing it all.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, and we can get that. And so HE1523, for example, that one is really bright Only it's a red giant, so it's intrinsically bright and it's fairly close. And so the data I got for that was insanely good. And that yielded this uranium detection and thorium detection. I can never get that kind of data for a dwarf galaxy star. So that's a big trade-off. But the environmental information that we get along with the basic information about these stars in each dwarf galaxy is really, really valuable in establishing, for example, these site information, right? Because the galaxy is still there, so nothing crazy could have happened. So to close that loop,”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“To know That's a hard one. I mean, I love them all, of course. They serve different purposes. The stars in the Milky Way, I can get much, much, much better data for them because they're brighter. They're closer. So they're brighter. And that tickles my fancy.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“They're all really ancient because actually, as it turns out, if you have a small galaxy, there was a process early on in the universe called reionization that kind of heated up everything. And together with some supernova explosions in an early shallow bound system, all these little systems lost their gas. It was sort of blown out or it simply evaporated or both, probably both. And so these systems have been unable to continue to form stars since. So it's the best for us, stellar archaeologists that you could hope for because it's a whole bunch of stars still sitting there. It's not just one. It's a whole bunch of them still sitting there ever since and nothing has literally nothing has happened to them. They've just been waiting there for us.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, because they're fairly close, and we detect actual individual stars I've observed some of the fainter stars You possibly observe with current telescopes in these dwarf galaxies because I was like, I need to know what the chemical composition is because there are leftovers from the early universe, right? They did not get eaten. So they are still in their native surroundings. It's like getting the lions in the wild, right? I got to study those And compare to the counterparts that got eaten and are now in the Milky Way. And so”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“It totally is going to be eaten. I can't tell you exactly when. Yeah, the Milky Way remains surrounded by dozens of small dwarf galaxies. There are collections of stars. Some of them, we call them ultra faint dwarf galaxies because they now only contain, I don't know, a few thousand stars, very, very faint”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, yes. And so now we find reticulum 2 and it has the stars show the signature of the rapid neutron capture process, the R process, and we are like, okay, these stars are located in a dwarf galaxy right now. We have environmental information. They are not lost in the galaxy where we don't know where they actually came from. No, we know these stars were formed in that galaxy because they're still in it. And that we already deduced from that that it must have been a neutron star merger that went off in reticulum 2 at early times, that polluted the gas from which all our little stars formed.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“We weren't looking for that. I actually wanted to prove that they had really low levels of heavy elements because that's what we had seen in all the other dwarf galaxies. And I was dead set on showing yet that that is yet the case again and that that is a typical signature of early star formation. We already talked about low strontium and barium abundances and the oldest stars, right? This is what we had seen anecdotally in the ancient dwarf galaxies that are surrounding us.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“It's a bunch of fabric. So that confirmed that one of the sites for sure is for the R process to occur is neutron star mergers. Interestingly enough, I have to mention this here, a year prior in 2016, my former grad student Alex G and I, we discovered a small dwarf galaxy. Is currently orbiting the Milky Way. It's called Reticulum 2 that was full of ancient iron deficient stars. Also had a strong signature of these heavy elements exactly like HE1523.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“This is neutron's galore, right? It's really violent to smash two neutron stars that are so dense already into each other. And in 2017, one of these events occurred and the LIGO and Virgo gravitational wave observatories, they detected that. And then the astronomers pointed their telescopes in that direction and they indeed observed what we call the electromagnetic counterpart. So there was something seen in the sky that faded over the course of two weeks. And that light curve, that light was exactly what you get when you create all these heavy neutron-rich nuclei in the R process and then the neutron flux stops and then it takes about two or three weeks for most of them of these nuclear to decay to stability. So we saw, the astronomer saw in this electromagnetic counterpart the nucleosynthesis of heavy elements occurring.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“The space time continuum basically, what do people say, the ripples of space-time? It's like you drop a rock into water, right? You see the waves coming. So that's exactly what happens when two neutron stars emerge.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Gravitational wave observatory. I mean, we know already that before, but now it's been measured by LIGO. These two neutron stars, they will orbit each other for like forever, but in the process, they will lose energy. So that orbit is what we call it, the orbit decays. And eventually the two neutron stars will merge. And that results in an explosive event that has roughly the energy of a supernova, but the process is completely different. And the cool thing is when these two neutron stars collide, they produce a gravitational wave signature because neutron stars are super dense objects. They are like giant atomic nucleuses. So there's a lot of interesting physics happening already. And so if you basically form a super neutron star by smashing two into each other, more interesting physics happens. And that means that there's this ripple sent out into the space.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, that's right. And so there are not that many options, right? So, where do you find lots of neutrons in the universe? Well, it's neutron stars, right? Neutron stars form in the making of supernovae of the explosions. Okay, so maybe some of this heavy material gets sort of made in the making of the supernova explosion and then gets expelled. you have neutron stars so the you know if the neutron star survive i mean usually that's the leftover of a supernova if you have two from a binary pair so stars usually show up in pairs and so it's not too unusual to um create a pair of of neutron stars that will still orbit each other after both of their progenitor stars have exploded and those two neutron stars will orbit each other diligently but as we know now thanks to lIgo”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“And the whole thing is done within two seconds. So, just to add to the rapid here Literally the snapping on my hand, it's all there. In my talks, I often, I have this nice simulation that illustrates this creation of these heavy nuclei. And I always say, this is the only simulation you will ever see that's slower than real time. Because in astronomy, you know, we show, oh, this is how galaxy forms 13 billion years in 30 seconds really short, right? This is the opposite me showing you this, the elements are a long, long made.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“If you know bombard lots and lots and lots of neutrons onto that seed nucleus within that timescale of the beta decay, that's how you get to this huge fat neutron-rich nucleus that then wants to decay, right? So the rapid process as you have your seed nuclei, they get bombarded, you create these really heavy neutron-rich nuclei heavier than uranium even. The neutron flux stops and then all these heavy nuclei, they decay and they make all these stable isotopes that we know of all the way up to thorium and uranium.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“We can surmise and ponder where that might be the case. But you have this iron atom and you bombard it with neutrons and you do it incredibly fast. Now what happens in the process? That iron atom, you know, you collect lots of neutrons, it becomes really big and unstable. So it's a heavy neutron-rich nucleus. Wants to decay because it's not stable, it's way too big. And so let's say you add only one neutron to it, that would already make it unstable. So it will then, it has a characteristic decay time that's called the beta decay time scale. So it will decay to a stable nucleus. So the neutron will convert to a proton and that makes it stable.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Which, you know, to folks on us on Earth is a really long time, but those kind of timelines are really good when you want to explore the early universe. So there are two questions now that kind of come to mind. Where do these elements come from? And what do they tell us, right? And these, as we know, these heavy elements are made in a specific process. It's a neutron capture process, usually referred to as the R process for rapid neutron capture process. We talked about seed nuclei before, right? So we still don't exactly know where this process can occur. So you have, let's say, a lone iron atom somewhere, and it is in an environment where you have a strong neutron flux, which means there must be lots of neutrons around. And again, when we talk about the site.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“And again, that was the second of its kind. But the uranium abundance could be more well determined. So we had a better grasp on that. Now, why a thorium and uranium interesting, they are radioactive elements. They decay. Thorium has a half-life of 14 billion years, I believe, and uranium of 4.7.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“Yeah, so that one isn't quite as iron efficient as the other one. So probably not a second generation star, but easily second, third, sorry, third, fourth, fifth or so. We can't really pin it down, but it's also not super important for us. What is important is that that star has a very different chemical composition in the sense that, yes, we have all the elements up to iron there. They have sort of normal ratios, which means kind of the same as most other old stars and not too different from the sun, or at least different in quantifiable ways. But it has this huge overload of very heavy elements. And what was so nice about that stand particular was that I could measure the thorium and the uranium abundance.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source
“And so much could have gone wrong, and there would have been another outcome, you know. And it's actually amazing how many things kind of fell in place. I mean, maybe that's all sort of self-deterministic in some ways, right? We are who we are because that was the path. Maybe we would have ended up being robots. I don't know. But it's certainly wonderful to scientists for us to help contribute unraveling our cosmic history, right? I always say the biological evolution on Earth was absolutely facilitated by the chemical evolution of the universe, right? And one doesn't go without the other.”
2023-05-18 · Lex Fridman Podcast · #378 – Anna Frebel: Origin and Evolution of the Universe, Galaxies, and Stars · IDENTIFIED FROM THE TRANSCRIPT · source