[HN Gopher] Astronomers detect almost 100 new extremely metal-po...
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Astronomers detect almost 100 new extremely metal-poor galaxies
Author : wglb
Score : 86 points
Date : 2023-12-16 04:37 UTC (18 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| evanb wrote:
| In astronomy 'metal' is shorthand for 'all elements except
| hydrogen and helium' [0]. This is a convenient shorthand because
| big bang nucleosynthesis [1] produces only minuscule amounts of
| lithium and even less heavier elements. Nonnegligible presence of
| elements beyond helium is indication some stars' life cycles
| completing and their insides being distributed via explosion. So,
| being metal-poor is an indicator of very young age.
|
| [0] https://en.wikipedia.org/wiki/Metallicity
|
| [1] https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
| vlovich123 wrote:
| Is our solar system considered metal poor?
| abainbridge wrote:
| No. I believe a metal poor solar system wouldn't have rocky
| planets.
| vlovich123 wrote:
| But our sun is quite young afaik (middle aged) and earth is
| not much younger so it's weird to hear the reasoning that
| metal-poor systems implies young system...
| metafunctor wrote:
| Here, "young" means measured from the Big Bang.
|
| Our sun is made from the stuff of previous stars.
| codeflo wrote:
| I'm assuming the poster misspoke and meant that metal-
| poor stars have formed when the universe was relatively
| young, not that the stars are young. It's also my
| understanding that a planet such as ours could only have
| formed a bit later, after enough supernovae had formed
| all the carbon and iron and so on that we need to live.
| Sharlin wrote:
| Making matters confusing is the fact that the phrase "a
| young galaxy" is commonly used to refer to a galaxy
| formed when the universe was young - if it's far away
| (high redshift, z >> 1) and as such we see it the way it
| was when the universe was young!
|
| This specific study, however, looked for more nearby
| galaxies (z < 1, we see the light that was emitted a few
| billion years ago) so these galaxies (as we see them) are
| in fact "old".
|
| I think essentially all existing galaxies either formed
| >10 Gy ago or are the results of galaxy mergers - so in
| that sense there are no "young", recently-formed galaxies
| in the universe at all as the raw material was long ago
| used up. As such in astro-talk "young galaxies" can
| fairly unambiguously mean "far-away galaxies". But
| formally they'd be called high-z or high-redshift
| galaxies.
| rbanffy wrote:
| > after enough supernovae had formed all the carbon and
| iron and so on that we need to live.
|
| And let's not forget some of the atoms we see around us
| have been through even more violent events than
| supernovae.
|
| Population II systems must be very boring.
| pvg wrote:
| 'Metallicity' in that sense is used to describe stars and the
| Sun, being a relatively young star is metal rich.
|
| Edit: 'young' is confusing here as pointed out in sibling
| comments - young compared to the age of the universe rather
| than young in terms of stage of stellar evolution. To make
| this even more confusing, this is 'population I' - younger
| and more metal rich unlike older, metal-poor 'population II'
| stars.
|
| https://en.wikipedia.org/wiki/Stellar_population#Chemical_cl.
| ..
| vlovich123 wrote:
| Ah ok. So this is about the composition of just the star
| and not anything about the broader system.
| pvg wrote:
| Yeah although like most things in exoplanetary astronomy,
| the relationship between metallicity and planetary
| systems is an area of active research with various not-
| totally-intuitive findings:
|
| https://www.space.com/31456-rocky-planet-found-unlikely-
| star...
|
| https://www.nature.com/articles/s41467-023-37195-4
| spookie wrote:
| That Neptune sized planet sure is close to its star.
| Interesting
| pvg wrote:
| Oh they get even bigger and closer and we've seen a bunch
| of those because they're more readily detectable:
|
| https://en.wikipedia.org/wiki/Hot_Jupiter
| defrost wrote:
| Almost pretty much the same thing really.
|
| Consider that our sun contains 99.86% of the mass of our
| Solar System.
|
| Bear in mind the headline is about total spectrum of
| elements in entire galaxies ... eg: as in looking at our
| galaxy, the entire milky way, from a distance that makes
| it dwindle to a near point and difficult to estimate how
| many stars make it up.
|
| Of all the many galaxies that we can see, this is a story
| about a handful that are mostly hydrogen and helium ..
| more so than what we see as typical for galaxies.
| pvg wrote:
| _Almost pretty much the same thing really.
|
| Consider that our sun contains 99.86% of the mass of our
| Solar System._
|
| If you dumped that into a Sun-sized metal-poor star, it
| would probably pass for metal-rich.
| defrost wrote:
| Given our sun is a population I or heavy-element-rich
| star that'd almost certainly be the case ... the elements
| that didn't fall into our sun to make it so remained in
| orbit and are also heavy element rich (obviously
| _relatively_ more so that the mostly H-He sun).
|
| A Sun sized metal poor star wouldn't be surrounded by
| large amounts of orbiting heavy elements .. that would
| suggest even larger amounts failed to orbit and fell into
| that star.
|
| ( I'll freely confess to being decades out of date on the
| conjectured life of stars though, these days I mainly do
| geophysics related to astrophysics (cancelling out ground
| effects from SKA type projects) )
| pvg wrote:
| Oh I just meant that amount of metal for some (entirely
| made up) stars would already be pretty metal. The sort of
| astro out of an Asimov joke story.
|
| _But as the black hole approached, Hieronymus noted
| there was no gravitational effect. He studied it more
| closely and announced, with a chuckle, that it was not a
| black hole after all.
|
| "It's nothing," he said. "Just an ordinary asteroid
| someone has painted black."_
| ozfive wrote:
| Being able to identify both is a feat.
| dudeinjapan wrote:
| We have Black Sabbath, Iron Maiden, KISS, Slayer, and
| Megadeth. I'd say we are doing alright!
| DiogenesKynikos wrote:
| Everything you say is correct up until the last sentence.
| Metal-poor stars tend to be _old_ , because the metallicity of
| galaxies is increasing with time (as fusion in stars and
| supernovae combines light elements into heavier elements).
| maxnoe wrote:
| Young relative to their own lifetime, old relative to us.
| evanb wrote:
| I meant young as maxnoe suggests but you're right obviously,
| a better less ambiguous thing to say is that they are from a
| time/place when/where no other stars have yet had the
| opportunity to die.
| ozfive wrote:
| Wait. That's an interesting statement. "Had" is the keyword
| which implies dual realities.
| magicalhippo wrote:
| Guess a better way to phrase it is that metal-poor stars were
| formed long ago, relatively early after the big bang. If
| they're old or young depends on where in their lifecycle we
| observe them.
| sandworm101 wrote:
| Not age of the star but experiance of the material that formed
| the star, how many past stars was it baked in. There may be
| some pocket of virgin bigbang hydrogen out there that could
| theoretically form a new low-metal star.
|
| A low-metal/high-mass star could be a technosignature of a very
| advanced civilization. Nobody would dare mess with anyone
| capable of building themselves a new star out of only hydrogen:
| the ultimate keep off my lawn sign.
| LeonB wrote:
| If I were* the median atom in the universe, how many times
| would I have been through a full star cycle? 0? 1? 3000?
|
| * I'm not, but I'm just saying, "If I were" (but I'm not)
| anon25783 wrote:
| Zero. Of all the atoms in the Universe, about 98% are
| primordial hydrogen and helium[1], "primordial" meaning
| they formed very shortly after the Big Bang.
|
| [1] https://en.wikipedia.org/wiki/Abundance_of_the_chemical
| _elem...
| simonh wrote:
| That's not quite the same question. Most of the
| primordial hydrogen that goes through stars isn't fused
| into anything else and therefore is still primordial
| hydrogen, but it has been in one or more stars.
| LeonB wrote:
| Who's to say it hasn't been through a dozen stars? Or a
| thousand? It could've blinked into existence five minutes
| ago.
|
| (I could be wrong)
| throwup238 wrote:
| Most of the universe is primordial atoms that haven't fused
| yet but if you were to take an iron atom, it probably would
| have been through only one star cycle.
|
| A main sequence star at least ten times the size of the sun
| goes through several stages as it ages: hydrogen, helium,
| carbon, neon, oxygen, and finally silicon burning. The
| silicon burning stage produces abundant iron and the type
| II supernova that follows spreads it around.
| idiotsecant wrote:
| Such a civilization wouldn't have much incentive to build
| 'keep off my lawn' signs, I don't think, given that the
| answer to such an advertisement should be a trillion
| relativistic snowflakes aimed at every system within a
| thousand lightyears. Anyone observing such a show of power
| would have no choice but to act first before that
| civilization did it to them.
| astroH wrote:
| While in general, 'metal' means all elements except for
| hydrogen and helium, in this specific case, 'metal' really
| means oxygen. They are using the measurement of the [O III]
| 4363 line to estimate a gas temperature which allows for a
| determination of oxygen abundance but this gives no information
| on the other elements. One thing to keep in mind is that the
| method they use, while considered the gold-standard, is known
| to be biased such that metallicity is guaranteed to always be
| underestimated. Regardless, these galaxies are still metal-poor
| but it's not clear how well they mimic those in the early
| Universe which is one of the primary motivations for studying
| such objects.
| thangalin wrote:
| My coffee table photobook shares a timeline of metal-poor stars:
|
| https://impacts.to/downloads/lowres/impacts.pdf
| pineaux wrote:
| Nice timeline. So the future is golf fields with windturbines?
| egberts1 wrote:
| Basically, how metal a galaxy is how many times a star is born,
| expands then collapsed as it rotates around its galaxy.
| dang wrote:
| [Stub for offtopicness]
| kazinator wrote:
| Original should say "extremely metal-poor".
| TaylorAlexander wrote:
| Maybe they're poor and extremely-metal.
| smellf wrote:
| Even if they were you still wouldn't hyphenate there.
| ReptileMan wrote:
| So - all the power and black metal bands in europe?
| troymc wrote:
| Like the Tin Man in _The Wizard of Oz_.
| johntiger1 wrote:
| Honestly I considered this interpretation for far too long
| - "extremely-metal" but poor. Now what that means I don't
| know, but I thought it might have related to something an
| astronomer could tell me
| dang wrote:
| I was waiting for this interpretation. Alas, fixed now.
| raziel2701 wrote:
| Aliens mined the metal, no other explanation.
| gumby wrote:
| That would argue for them being extremely _old_ then.
| supportengineer wrote:
| There must be incredible treasures all over the galaxy. If
| only we could go exploring.
| ozfive wrote:
| The treasures are built from the mind and I suppose
| hierarchical structures of the mind based on scarcity.
|
| I didn't downvote you. Just want to remind people that it
| isn't an absolute.
| onion2k wrote:
| This is a fascinating thing to consider - humans are
| either boring because there's aliens all over the place,
| or we're pretty much unique because life is incredibly
| rare.
|
| If we're not unique then it doesn't really matter if we
| wipe our species out. We'll just get chalked up to the
| great filter and some other species will do some
| archeology on Earth in the future.
|
| I find the idea that we're unique much more interesting.
| If we are then we're effectively the guardians of the
| only intelligent life in the universe, and we should be
| doing a lot more to preserve it. Maybe there aren't
| treasures all over the universe. Maybe they're all here
| on our planet (and a few on the moon and Mars).
| NooneAtAll3 wrote:
| but only extreme metals
|
| and money, that galaxy has no money
| anacrolix wrote:
| Cow kills man with axe
| ozfive wrote:
| Entropy.
| porbelm wrote:
| Ugh, that hyphenation!
| insickness wrote:
| Poorly written-title! They got it right in the article
|
| > Extremely metal-poor galaxies (XMPGs) are the ones with
| metallicity...
| jjgreen wrote:
| Those galaxies really need more extremely-metal.
| mixeden wrote:
| what about gpu-poor galaxies, any news?
| teaearlgraycold wrote:
| You're in one buddy
| BurningFrog wrote:
| "Astronomers detect 95 new extremely-metal poor galaxies" would
| have been a better headline IMHO.
| BigTuna wrote:
| Just think of the billions of planets out there that have never
| heard Black Sabbath
| johnohara wrote:
| Or the plutonium rock band Disaster Area. Long live Hotblack
| Desiato until taxes are due.
| davidw wrote:
| I came here to write that we need to put Ozzy on a spaceship
| and send him there to redress their lack of metal.
|
| "My time on earth is nearly done... I am going to rock on
| among the stars"
| nhatcher wrote:
| A really beautiful book about the subject is Anna Frebel's
| "Searching for the Oldest Stars". One of the best books I've read
| on popular science in the last few years. I am in awe of what we
| can understand looking at those objects
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