[HN Gopher] Light from a rare isotope of helium in a distant galaxy
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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.
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(page generated 2023-01-30 23:00 UTC)