[HN Gopher] James Webb Space Telescope Finds Most Distant Known ...
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James Webb Space Telescope Finds Most Distant Known Galaxy
Author : ArnoVW
Score : 75 points
Date : 2024-05-30 17:40 UTC (5 hours ago)
(HTM) web link (blogs.nasa.gov)
(TXT) w3m dump (blogs.nasa.gov)
| nhatcher wrote:
| This is breathtaking. I marvel at what we are able to see. Small
| quibble though: I wish they would say, '... finds galaxy with the
| highest known redshift.' Maybe not so pompous, but especially
| after all the recent news about the size and age of the universe
| due to JWST observations.
| ziddoap wrote:
| I'm not sure I understand your distinction, can you explain why
| you wish that?
|
| My understanding is that there is a linear correlation between
| the redshift of a galaxy and the distance to the milky way (for
| distant galaxies where the peculiar velocity is negligible).
| So, the most redshifted galaxy is the most distant galaxy.
|
| But, I'm just a layman who enjoys astronomy, so I'd appreciate
| an explanation on why the distinction is important.
| nhatcher wrote:
| You are right, of course. But that is based on our standard
| cosmological model.
|
| But there is some controversy in this respect. It is not as
| clear cut as the relationship with C14 and age, for instance.
| There are some recent discoveries of galaxies that if their
| age and distance are correct clearly contradicts the standard
| cosmological model. But, even if I am right, it is a small
| nitpick. I think from this news I rather just wonder.
| mr_mitm wrote:
| It's linear for small redshifts only. In general it depends
| on what distance you mean, but it's never linear. This does
| not change the validity of your argument of course.
|
| Check https://en.m.wikipedia.org/wiki/Distance_measure
| XzAeRosho wrote:
| >The presence of oxygen so early in the life of this galaxy is a
| surprise and suggests that multiple generations of very massive
| stars had already lived their lives before we observed the
| galaxy.
|
| For some reason this quote blew me away. It's just so hard to
| comprehend the timescales and vastness of the universe.
| colechristensen wrote:
| Very large stars live very short lives.
|
| Our star will live 10 billion years, the smallest stars will
| last trillions of years, the largest stars live less than 10
| million years and some very early stars broke the models for
| how big they were and maybe lived much less long.
|
| What happens is their cores go through stages of fusing an
| element until they run out, gravity takes over and shrinks the
| core until the next element ignites, fuses, and runs out, down
| to iron. At one of those stages the collapse triggers a
| supernova (or one of the class of ways a star can die) instead.
| vlovich123 wrote:
| It's interesting that [1] has a diagram showing that in 2022
| the NASA diagram claimed that stars & galaxies formed 400M
| years ago so this feels like a big shift to having a massive
| galaxy already at 300M with data suggesting it's formed after
| several generations of stars.
|
| > All of these observations, together, tell us that JADES-
| GS-z14-0 is not like the types of galaxies that have been
| predicted by theoretical models and computer simulations to
| exist in the very early universe
|
| This is exciting. Maybe our understanding of the Big Bang is
| extremely flawed & this data is just the first inklings that we
| have to reimagine what we know about it?
| dylan604 wrote:
| > formed 400M years ago
|
| do you mean formed 400M years _after the big bang_ instead of
| 400M years ago from today? That 's like yesterday to the
| Universe.
| Pompidou wrote:
| No. The diagram https://science.nasa.gov/resource/history-of-
| the-universe/ tells us that galaxies and dark matter formed
| 400M years after the big bang. Look at the right of the chart
| legend: "13.8 billion years" is above "today".
| astroH wrote:
| Multiple generations is perhaps an overstatement. The first
| oxygen in the Universe came from what we call Population III
| stars which is the first generation of stars to form after the
| Big Bang and what separates these from other stellar
| populations is that they do not have elements heavier than
| hydrogen or helium (except for minuscule traces left over from
| the Big Bang but these are insignificant). Now we don't know
| much about Population III stars but many models predict they
| are massive and when they die, can release 60 times the mass of
| our sun in the form of oxygen. That's really a lot of oxygen so
| you don't need too many of these to go off to pollute the early
| Universe and probably one of the reasons why we haven't yet
| found Population III stars.
| malfist wrote:
| Big stars burn hot and fast, the more mass, the shorter their
| lives
| throwawaymaths wrote:
| Pop III stars (if they existed) are really a mystery, we
| can't easily extrapolate. These stars would be purely
| hydrogen and helium so it would take them a surprisingly
| long time to get to CNO cycle, for example.
| astroH wrote:
| So I think it is fair to say they did exist. If we
| believe in Big Bang Nucleosynthesis then heavy elements
| had to come from somewhere making the first generation of
| stars (whatever their properties may be) be Population
| III. I agree that without a catalyst it's hard to
| initiate the CNO cycle but indeed models predict that it
| is possible even under these circumstances.
| bmitc wrote:
| The scale of both time and space are the least confusing things
| in our universe, to me at least.
| phaedrus wrote:
| I wonder if a galaxy like this could be so bright as to support
| life on rogue planets i.e. those not orbiting a star?
|
| (If there would be any elements to create a rocky planet from.
| However the article states they were surprised to detect signs of
| dust and oxygen already in such an early galaxy.)
| kloch wrote:
| Only maybe in the dense core of a galaxy because incident
| radiation falls off with the square of distance.
|
| The nearest star to us after the Sun is ~4ly away, or ~250k AU.
| The Sun would have to be ~63 _billion_ times brighter to give
| the same incident radiation at 250k AU, and that is just a
| typical distance between stars in our neighborhood . The Sun is
| also brighter than the average star, especially the older stars
| that congregate near the galactic center.
|
| Galaxies can easily have 1 trillion stars but they are usually
| so spread out as to make this impractical. This is also why the
| Milky Way, Triangulum, LMC, SMC, and Andromeda (nearest
| galaxies) are so faint to the naked eye.
| koolala wrote:
| Is it cool or warm there?
| dylan604 wrote:
| Curious minds do want to know what type of outfits to pack when
| visiting.
| nerdjon wrote:
| It is interesting to think about what could be from a galaxy that
| was formed ~500 million years before ours.
|
| If life had formed in that galaxy, if somehow it had followed a
| similar pattern we did (which is doubtful, but just a thought
| experiment for simplicity). It would be very interesting to see a
| glimps of where life could be with an "extra" 500 million years.
| Even just a few million considering homosapiens did not appear
| until ~300,000 years ago.
|
| It is almost sad in a way that we now know this galaxy exists,
| but we will always be looking at it 13+ billion years away and
| will never know what it is now. Can never really compare what
| that 500 million year head start got it (assuming it still
| exists).
| ajross wrote:
| Just to rub it in, it's worse than that: it's always flying
| away from us, and it looks currently like that rate is
| accelerating. We don't even get to see this galaxy evolve, as
| we watch it will eventually appear to freeze in time from our
| perspective as it dims and red-shifts into the background
| radiation.
| boringg wrote:
| Anyone know the algorithmic approach to finding this? I assume
| they ran an ML over the dataset with a search function to figure
| it out.
| astroH wrote:
| It's a lot less sophisticated than that. They take images in
| multiple filters. In the context of JWST of order 10 filters
| (sometimes more sometimes less). Source extraction is then
| performed on the images by essentially identifying bright spots
| and dropping an aperture (separating ones that are nearby and
| blended if possible). The standard tool for this is called
| source extractor. They then have catalogs of tens of thousands
| of sources per image and the next step is to figure out
| redshift. There is a lot of code to do this but the simplest
| methods require fitting templates of what we think galaxies
| look like to these catalogs. High redshift sources tend to
| "drop" out of filters at shorter wavelengths. This is because
| neutral hydrogen in the early universe essentially absorbs
| almost all of the light at shorter wavelengths than 1216
| angstroms. So if a galaxy is at redshift 10, the flux should
| essentially be zero at all filters that cover wavelengths
| shorter than 1.33 microns. JWST has filters both bluer and
| redder than this wavelength so we see the source appear in the
| redder filters and not the bluer ones. This technique was
| pioneered in the mid 1990s. This gives an approximate redshift
| called a "photometric redshift". There are other features in a
| galaxy spectrum that can mimic this "dropout" so not all
| photometric redshifts are robust. Therefore one has to take a
| spectrum of the galaxy which was what was done in this paper to
| confirm that the dropout is in fact the absorption feature we
| think it is. In this particular case, the authors were
| skeptical early on because there is a source right next to the
| object that is at a redshift where one of these other spectral
| features can mimic absorption by neutral hydrogen (this feature
| is the Balmer break). In any case, it's really an impressive
| demonstration of the power of JWST.
| gwerbret wrote:
| For any astronomers here, or others with the relevant knowledge
| of astrophysics, a question: this discovery would suggest the
| existence of a fully-formed galaxy at ~290 gigayears (Gyr), when
| the _first_ stars are presumed to have emerged between 200 and
| 300 Gyr. How badly does this damage current models of early
| galaxy formation, and what new physics might it suggest?
| astroH wrote:
| I wouldn't say it's too damaging yet. There is a general trend
| where these early galaxies are brighter than we had thought by
| simply extrapolating models that were built prior to JWST, but
| these make numerous assumptions on how efficiently stars can
| form and the properties of these stars. Mildly relaxing any of
| these assumptions can easily solve the problem within our
| current framework and not significantly change what happens
| later in the evolution of the Universe.
| csiegert wrote:
| Your unit is wrong. Giga means billion. The universe is ~14 Gyr
| old.
| forgot-im-old wrote:
| "The data reveal other important aspects of this astonishing
| galaxy. We see that the color of the galaxy is not as blue as it
| could be, indicating that some of the light is reddened by dust,
| even at these very early times."
|
| We continue to see evidence that the universe is older than first
| believed.
| brcmthrowaway wrote:
| Enough of this
|
| We need a Manhattan level project to find life.
|
| That's it.
| perihelions wrote:
| - _" Editor's Note: This post highlights data from Webb science
| in progress, which has not yet been through the peer-review
| process."_
|
| Here's the preprint they won't link:
|
| https://arxiv.org/abs/2405.18485 ( _" A shining cosmic dawn:
| spectroscopic confirmation of two luminous galaxies at z~14"_)
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