[HN Gopher] Light from a rare isotope of helium in a distant galaxy ___________________________________________________________________ Light from a rare isotope of helium in a distant galaxy Author : theafh Score : 119 points Date : 2023-01-30 15:31 UTC (7 hours ago) (HTM) web link (www.quantamagazine.org) (TXT) w3m dump (www.quantamagazine.org) | FreeHugs wrote: | Astronomers Say They Have Spotted the Universe's First | Stars | | Isn't the size of the universe potentially infinite? | | If that is the case, we can see only an infinite small fraction | of the stars in the universe. Under that assumption, I find it | hard to have a concept of what spotting the universe's first | stars could mean. | | The oldest stars among those that we can see? | [deleted] | chaps wrote: | What does size of the universe have to do with this? ;) | | The question is about the relationship between the age of the | universe (well, after the big bang) and stars that came into | existence afterwards. We have a pretty good idea how old the | universe is, and with the universe expanding, light from the | early days of the universe still makes it to earth from | billions of light-years away. | svachalek wrote: | You could postulate that we arised from A Big Bang rather | than The Big Bang, and somewhere outside the visible universe | some alien species watched it happen. At least as I | understand things, nothing we know about the visible universe | puts any constraints, age or otherwise, on the rest of it. | | But for similar reasons, unless some fundamental | understanding of time and space changes, nothing outside the | visible universe really matters. | ben_w wrote: | > The oldest stars among those that we can see? | | Yes. | | If I've understood the lectures correctly, time isn't really | well-ordered, and on scales like this the deviation makes a | substantial difference. | | However, what we are looking at in cases like this is stars far | enough away that the light took most of the age of the universe | to reach us, so it's not unreasonable to call those stars | (members of the set of) "the Universe's First Stars". | xwdv wrote: | First generation stars are so massive, couldn't there be vast | numbers of planets in habitable zones orbiting one? Seems good | for a sci-fi setting with feasible interplanetary travel and | trade amongst many different worlds. | astroH wrote: | Unfortunately not. These stars have no elements heavier than | hydrogen and helium so you wouldn't be able to create a rocky | planet that's habitable. Furthermore their lifetimes are only 3 | Myr which is much to short to form a rocky planet and also the | explosion from SN if it happens or direct collapse of the star | to a black hole would immediately destroy any life. | xwdv wrote: | Ah fuck, there goes that idea then I guess. | zopa wrote: | Set it in Universe N+1 of a multiverse and mix in a tiny | dusting of metals and such from Universe N. | | Or maybe it's a synthetic population III star, made for | unknown purposes by a now-vanished civilization. You're | allowed to make up whatever you need to get the story | going. | h2odragon wrote: | interstellar travel is so pasky, irritating and slow. A | civilized culture might well cultivate such systems so | that they could have a huge number of worlds in easy | range of each other. | | Allow them those abilities and you might as well be | importing already inhabited worlds from wherever you | like, which saves time. | astroH wrote: | As an expert in this space, I can confidently tell you that | nothing about this observation is conclusive about the presence | of the "First Stars" or what we call "Pop. III" Stars. By | definition, the first stars are nearly completely devoid of | elements heavier than hydrogen and helium. The spectra shows | absolutely booming emission from Oxygen III ions at 5007A so | there are heavy elements in the system and at best there is a mix | of Pop III stars and more normal stars. The lifetimes of the | stars are very short, ~3 Myr, so the chances of seeing them are | very low which is likely the limiting factor (along with their | brightness) and thus there is a strong Bayesian prior against | seeing them with a narrow field of view. The mass of the system | at 10^7.35 solar masses is much greater than what we expect from | theoretical models that form Pop. III stars and you must ask how | it's possible to not have any metals pollute the gas. The main | piece of evidence for Pop III stars is HeII emission at 1640A | which is a prediction of Pop. III stars, but you can also get | this in many other ways, for example X-ray binaries. We see this | plenty in the local Universe and we fully expect this to happen | elsewhere. So to me this is headline chasing with little | conclusive evidence. | LarryMullins wrote: | > _" First Stars" or what we call "Pop. III" Stars. By | definition, the first stars are nearly completely devoid of | elements heavier than hydrogen and helium._ | | I thought Pop III stars _initially formed_ with only Hydrogen | and Helium, but they promptly created heavier elements up to | Iron within themselves through fusion. | dguest wrote: | They create most of the heavier stuff when they blow up. But | that's a pretty small fraction of their lifetime, even for | stars with a relatively short lifetime (a supernova takes | minutes, these things live for millions of years). | astroH wrote: | Indeed, but we define their "metallicity" (mass fraction of | elements heaver than helium) typically by the gas that they | formed from. And the key point is that since they form from | metal-free gas, you don't expect to see emission lines from | metals which come from the star illuminating the surrounding | gas with radiation. | LarryMullins wrote: | It makes sense to me that these stars would lack planets, | and metallic gases around them and whatnot. But wouldn't | you still get metal emission lines from the star itself? Or | can those emissions not escape the star because the heavier | elements are deep inside it? | soiler wrote: | I interpret | | > the star illuminating the surrounding gas with | radiation | | to mean that we're looking at the spectra of the gas | around the star, or at best the corona or maybe the | surface of the star. I think it's very difficult for | photons in the core of a star to reach the surface, so we | probably don't see light from the heavier interior | elements often or at all. | martincmartin wrote: | Inside the star, or even on the surface, there is a lot | of energy, so you won't see the light that specifically | comes from a single electron, in the first excited state | with a well defined energy, that then decays to the | ground state. | | At least that's my guess, I'm not an expert. | UI_at_80x24 wrote: | >~3 Myr | | Just curious, when you mentally say that do you pronounce it: | ~3 MEGA-years or ~3 MILLION-years | | I realized that I keep flipping it back and forth and I can't | settle on the 'correct' version. Like saying data vs data. =) | | In addition, thanks for the comment. The information on Pop. | III stars was great! | Natsu wrote: | Why do the populations seem backwards? You'd think the first | stars would be Pop. I, then the next Pop. II, then III, and | maybe someday we'd get to IV. Instead they seem to work | backwards? | LeifCarrotson wrote: | Because the names were determined by when they found those | groups of stars, rather than when the stars they found were | formed. They only later realized that their distinct | groupings based on observed metal content were caused by | stellar formation processes. | | Regrettably, the stars didn't show up in their telescopes | with labels and histories attached. | soiler wrote: | Same problem with categorizing star luminosity... I wish we | could make a shift to these cumbersome categories, but | cultural inertia is tough to overcome | JumpCrisscross wrote: | > _mass of the system...is much greater than what we expect | from theoretical models that form Pop. III stars_ | | I would have thought the mere presence of a solar system | excludes a star from Population III. Is that inaccurate? | [deleted] | dang wrote: | Thanks! I've replaced the overstated title with what seems to | be a better phrase from the first paragraph. If there's a | better (more accurate and neutral) title, we can change it | again. | perihelions wrote: | The "isotope" part is a mistake in the article. The writers | heard "He II" and very reasonably wrote down "helium-2", and | added some exposition about that (hypothetical) nuclear | isotope. But they're in fact unrelated things: "He II" in | this context is an ionization state of helium (the +1 state) | -- not an isotope. What the research is observing is high- | energy radiation from stars stripping electrons from helium | atoms. No rare isotopes in sight! | astroH wrote: | I think this is perfect! If only we can convince the author | of the article... | omnicognate wrote: | Or the author of the headline at least. The article itself | is detailed and gives most of the caveats you did. | not2b wrote: | Yes, authors of articles rarely get to choose the | headline, at most, they can suggest one. The editors | choose the headline and often their motivation is to | maximize clicks. | | Ars Technica in particular sometimes uses A/B testing, | randomly giving readers one of two headlines to see which | one generates more clickthroughs (they've been | transparent about that, there was an article describing | it). | hinkley wrote: | You're saying a lot of things here, but is one of them that an | event could be detected far away because it's old, or because | it's such a rare event that the chances it happens near us are | vanishingly small? | xtreme wrote: | Pop 3 stars were formed in the very early universe and have | been long gone. So there is no way for us to see the light | they emitted without looking at the most distant galaxies. | [deleted] | astroH wrote: | These systems are very far away because you are looking more | than 13 billion years back in time. The argument is JWST has | a small field of view and these Pop III stars are like | flashes in comparison to the age of the galaxy. So the | probability of catching one that is bright enough to be | detected is just super low. Which is why there is a strong | prior that the HeII could be from other physics that is | relatively well understood. But really the OIII emission is | the biggest sign that this isn't a "primordial galaxy" | didntreadarticl wrote: | If we take the eventual heat death of the universe to be at about | 10^100 years, the era we are in with stars and so on only lasts | about 10^14 years. Which means light and stars and galaxies are | actually just a tiny tiny blip at the start of the lifespan of | the universe. Nearly all of the life of the universe will be dark | with no stars, just black holes and dark distintegrating rocks | and isolated particles. | | https://en.wikipedia.org/wiki/Future_of_an_expanding_univers... | | Sweet dreams | bena wrote: | This sort of thing always fascinates me. This is all true and | it absolutely does not matter. | | The thought of the universe sitting essentially idle for 10^86 | years seems like it should feel wasteful. But why? Wasting | what? Does our consciousness imbue the universe with any | special quality? | | It's all so weird. Even some of our most fantastical science | fiction only projects out a few millennia. | | Star Trek gets to the 31st century (or 3000s). Foundation is at | least 12,000 years in the future. Dune takes place from about | 23,000 to about 28,000. Warhammer 40k gets its name from the | fact it takes place in the 40,000s. The Time Machine reaches to | the 800,000s for the majority of its action. Red Dwarf is set | the furthest at 3,000,000-ish. | | All of which fall way short of even 1 billion years. The | Andromeda and Milky Way galaxies aren't scheduled to meet up | for another 5 billion. | | We aren't even a blip. | anjel wrote: | Try telling that to yeast | hinkley wrote: | They're all dead, everybody's dead, Dave. | bena wrote: | What about Peterson? | [deleted] | hinkley wrote: | _Everybody_ is dead, Dave. | bena wrote: | What? Todhunter? | kldavis4 wrote: | Since you mentioned some works of science fiction, this is | one thing that is pretty awesome about Cixin Liu's Three Body | Problem and how the series encompasses the present and all | the way past the end of our universe. It is a really jarring | perspective change for us as mortal humans that I think is | something that only well thought out science fiction can | accomplish. | euroderf wrote: | A great AR art project for the coming years would be to speed | up the collision with Andromeda by a factor of a zillion, so | that it takes place over a few years. | ridgeguy wrote: | Check out Vernor Vinge's Marooned in Realtime for a murder | mystery and love story that transpires over millions of | years. | lanna wrote: | > The thought of the universe sitting essentially idle for | 10^86 years | | 10^100 years minus 10^14 years is not 10^86 years. It is | roughly 10^100 years. | badcppdev wrote: | Small correction to your maths but not your sentiment. | | 10^100 years - 10^14 years = approx. 10^100 years | | In the same way that: | | 10^6 - 10^3 = 1,000,000 - 1000 = 999,000 which is more or | less approx. 10^6 | | Edit: Although this is one of those relatively uncommon | situations where it doesn't really matter if you're off by | 100 trillion years. | bena wrote: | True enough. I honestly did not care enough to do anything | but the most cursory attempt at math due to the scale | involved. 10^14 years and 10^100 are effectively equal | compared to even our entire species current lifespan. | Taywee wrote: | Yeah, it can be boiled down to "there will be stars for | longer than you can fathom, then there won't be stars for | longer than you can fathom". It's hard to really feel | much about different timespans that are all "forever" | relative to the entirety of human existence. | discretion22 wrote: | Not to give any special credence to Scott Adam's theory | that we are actually a simulation and co-incidences are | examples of the simulation re-using code, just today | youtube fed me a video of @misterwootube discussing 0 ^ 0 | in which he incidentally discusses division and | multiplication of x^y numbers; for division you subtract | and multiplication you add the ^y parts, so the math error | was treating the subtraction of the x^y as if it was a | division. Mister Woo looks fantastic - I'd never heard of | him before; worth a look, youtube.com/@misterwootube | thisismyswamp wrote: | This is meaningless, nothing about those numbers matters | neither does it say anything conclusive about the nature of | reality. It's just our best guess right now, and we are very | early. | Aperocky wrote: | I find this interesting about human nature, that is in the | want to believe in something eternal. | | Even if current theory about Universe is proven correct, it | will most likely have no effect whatsoever on current human | lifetimes. But doesn't preclude us from wanting to believe | that the universe is eternal and constant, that there will be | flashes of life and activity 10^50 years down the line. | thisismyswamp wrote: | I find the reverse interesting - this anti-conventional | desire to reduce scary questions to meaningless quantities | in order to intellectually one up everyone else. | jacquesm wrote: | Or, maybe they're just right. | edgyquant wrote: | Impossible to know but seemingly illogical. | GalenErso wrote: | I refuse to believe that the Universe isn't cyclical, because I | believe the Universe has existed forever, otherwise there is no | answer to the origin of everything other than something from | nothing or God. | kypro wrote: | I've often wondered whether something and nothing are just | concepts that only make sense from the perspective of a | subjective observer. | | Is `1 + -1` something or nothing? And what is `2 + -2`? Is it | something, nothing, or also `1 + -1`? And I could continue | like this proving every number you could possibly imagine can | exist in some manifestation of nothing. | | So perhaps we're just one of the infinite manifestations of | nothing. From our subjective perspective we are something, | but from the perspective of an objective observer nothing is | really happening because all the subjective manifestations | equate to nothing. | | I have no idea what I'm talking about, but this always made | more sense to me than trying to understand why there is | something and how long that something existed for. Perhaps | it's both. | gilleain wrote: | This reminded me of the idea of a 'block universe' - | | https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time. | .. | | which I first heard about in an interview with Alan Moore. | permo-w wrote: | why does there have to be an answer? | edgyquant wrote: | Saying there's no answer is no different than replying with | "God" as an answer | jacquesm wrote: | Because people like the mental comfort of knowing their | lives have meaning as foundation blocks in some eternal | building. To hear that it all ultimately doesn't matter is | not something most people are prepared to accept. The | answer to me is simple: live as if it does matter and don't | fret about the 'but what if it doesn't' question, anything | you'd do different because of that you are likely better | off without. | edgyquant wrote: | You're projecting here. Not all religions have some nice | eternal afterlife. | nh23423fefe wrote: | I'm a "nothing" doesn't exist person | nullspace wrote: | Amusingly (to me) the third attitude towards this is: "It | just is that way. I'm sorry that the answer does not satisfy | you, but the universe does not owe you a satifying answer." | :) | willis936 wrote: | The universe does not owe _an_ answer. Extrapolating 50 | orders of magnitude when we don 't even have an airtight | model of existing observations is... not something to be | confident about. It certainly won't affect my dreams. | GordonS wrote: | But... if there is a god, what created the god? | AnimalMuppet wrote: | Depends. Is the god eternal? Things that are eternal (at | least, eternal into the past) don't have beginnings, and | therefore don't need creators. (Same with an eternal, | cyclical universe - no creator required. It just is, and | always has been.) | nobody9999 wrote: | >Depends. Is the god eternal? Things that are eternal (at | least, eternal into the past) don't have beginnings, and | therefore don't need creators. (Same with an eternal, | cyclical universe - no creator required. It just is, and | always has been.) | | I'd add that if "god" is/was/will be made entirely of | photons (and/or other massless particles), then "god" | moves _at_ the speed of light, which means "god" doesn't | experience the passage of time[0]; so no beginning, no | end and no in-between, just existence outside of "time." | | This is, of course, a ridiculous idea. However, it does | support the fantasy of an eternal being. | | Then again, "there are more things in heaven and earth, | Horatio, than are dreamt of in your philosophy."[1] | | Which isn't to say that such claptrap as I suggest is | true and, based on what we know _now_ , it seems (at | least to me) a ridiculous concept. | | That said, our understanding of the universe(s) is | woefully incomplete. | | [0] | https://physics.stackexchange.com/questions/54162/how- | does-a... | | [1] http://www.shakespeare- | online.com/quickquotes/quickquotehaml... | | Edit: Used the correct conjunction. | edgyquant wrote: | The whole point of god is that it's the first cause. The | unmoved mover. | PUSH_AX wrote: | Why is one of those answers better than the other? | detrites wrote: | Occam's razor. A perpetual universe is only required _to | exist_ - which also happens to be all we can 100% | empirically confirm, whereas the other explanations require | creating extra complexity such as a birth /creator or | before/after. | | Even a before/after of "nothing" is still an extra | complication that violates the principle. Not that Occam's | razor is a law, but given something already as wieldy as | _everything_ , it's probably a prudent application. | pixl97 wrote: | A perpetual universe has it's own set of very complicated | problems, resetting entropy being the largest elephant in | the room. Occam's razor is still twisted into nth | dimensional shapes no matter what choice you make here. | | There are no easy answers, and it's highly likely | whatever answer is true is unknownable. | haswell wrote: | Believing one has a tendency to cause people to | fundamentally alter how they live their lives, optimize for | an afterlife at the expense of the life they actually have, | and then fight wars over the belief that the afterlife is | the only one that matters. | | As a default state of not knowing, one causes far more | material harm in our current reality than the other. | edgyquant wrote: | This seems like your biased interpretation actually. Most | people believe in God and most people don't start wars. | burkaman wrote: | Well God doesn't really answer the question, then you just | have to ask where God came from. I don't have a personal | opinion on "eternal universe" vs. "something from nothing", | they seem equally impossible and unfathomable. | PUSH_AX wrote: | I think they all spawn more questions equally. | edgyquant wrote: | Right now we have to ask where the universe came from. | God is literally a word that means "the answer to that." | The nature of god is a mystery. | efdee wrote: | But "forever" only makes sense within our universe, since | time itself is intrinsically a property of the universe. If | the universe exists within something else, "forever" doesn't | necessarily mean anything there. | Aperocky wrote: | This is YOLO on the universe level. | __MatrixMan__ wrote: | If this haunts your dreams, consider "The Life of the Cosmos" | By Lee Smolin, as antidote. In that book he proposes that each | of those black holes has a child universe associated with it, | some of which have sets of physical constants that allow for | grandchildren. | | It's a fun read. | ye-olde-sysrq wrote: | "How can the net amount of entropy of the universe be massively | decreased?" | andai wrote: | For the uninitiated: | https://users.ece.cmu.edu/~gamvrosi/thelastq.html | dontwearitout wrote: | Thank you for sharing this! | MichaelZuo wrote: | What does 'net amount of entropy' mean? | ye-olde-sysrq wrote: | You can already decrease entropy locally, but net for the | entire universe, entropy (as far as we can tell...) always | increases monotonically. And any action you take to | decrease local entropy still actually increases it in | total. | | So "The Last Question" is also basically asking - "how can | we avoid the heat death of the universe?". | | And phrased yet again differently: "Once all the stars burn | out and all the uranium is fissioned and the coal burned | and the universe is just a homogenous 5 degree kelvin soup | of [I'm sure some physicist could tell me whatever | fundamental particle it'll be that composes this soup] - | what then? Is that just it?" | twawaaay wrote: | Once all stars die you will be able to live very long off | of the heat of dead stars as they slowly cool off to | background temperature. | | And once those stars are completely cold, you can start | converting their mass into energy by dropping them into | black holes, piece by piece. | | And once you dropped all matter you could into black | holes you could live off merging black holes. | | And once you merged black holes you could live off of the | black hole radiation until all black holes evaporate. | | But this would be if the Universe wasn't expanding at a | growing rate. If the Universe is truly expanding at an | ever accelerating pace there will come a Big Rip which | will cause every fundamental particle to get further from | all other particles at speeds faster than light. And then | matter as we know it will cease to exist. | __MatrixMan__ wrote: | I think it means that the speaker is worried that they'll | be misunderstood, and they're trying to rule out other | (potentially incorrect) usages where: | | - entropy is not a measurable quantity | | - there's some other place, besides the universe, where you | might put all that problematic entropy | | Cautious usage like this is probably a good habit to be in | when talking with near-omnipotent computers. | bjornlouser wrote: | "Nearly all of the life of the universe will be dark with no | star" | | Maybe it will turn out that many of the double star systems | were created by intelligent life | ben_w wrote: | How are you thinking about stars in a way that double stars | will help? | SamBam wrote: | Isaac Asimov's _The Last Question_ is an excellent short | story that explores whether future civilizations will ever be | able to reverse entropy. [1] | | Also, Ten Chiang's _Exhalation_ is another short story about | trying to stave off the entropy-death of the universe. [2] | | 1. https://astronomy.org/moravian/C00-Last%20Question.pdf | (pdf) | | 2. https://www.lightspeedmagazine.com/fiction/exhalation/ | ericmay wrote: | I know this is probably a silly question but what is the | significance of locating earlier and earlier star formations | versus other objects? Is it because that's what we can readily | identify and improve accuracy of identifying? | chaps wrote: | Without those stars, we wouldn't have most of the elements we | have today. But these stars no longer exist, so we have to look | really far back. It's an important question! | perihelions wrote: | Am I blind or does the paper not mention helium-2 at all? | | https://arxiv.org/abs/2212.04476 | | It talks extensively about "He II", the astrophysics notation for | singly-ionized helium (a helium atom with one electron removed; | He+). That isn't notation for a helium isotope. I can't see | anything in the paper mentioning isotopes, nuclear reactions, or | anything in that direction. (?) | pfdietz wrote: | 2He is not being observed, as it is not a bound nucleus. | | And this is a good thing! If 2He were bound, the pp fusion | reaction would be much faster, our Sun would long since have | burned out, and we would not be here. ___________________________________________________________________ (page generated 2023-01-30 23:00 UTC)