a lot better...we can excite these atoms in a lab and simply measure what comes out. often times don't even need a model because spectroscopy can be fully empirical for many transitions
In my opinion, this article is misleading at best. "...scans of ancient galaxies gathered by the JWST seem to contradict the commonly accepted predictions of the most widely accepted Cold Dark Matter theory, Lambda-CDM." --> LCDM doesn't predict what galaxies should look like, it simply predicts how much mass is in collapsed structures and that dark matter haloes grow hierarchically. In contrast, with JWST we see light and need to infer what the underlying properties of the system are. It was shown very early on that the theoretical upper limit (i.e. taking all of the gas that is available in collapsed structures and turning it into stars) predicts a luminosity function (i.e. number of galaxies per unit luminosity) that is orders of above what JWST has observed (e.g. https://ui.adsabs.harvard.edu/abs/2023MNRAS.521..497M/abstra...). This means that there is plenty of space within the context of LCDM to have bright and seemingly large and massive galaxies early on. Based on current JWST data at these early epochs, there are really no convincing arguments for or against LCDM because it's highly sensitive to the galaxy formation model that's adopted.
> there are really no convincing arguments for or against LCDM because it's highly sensitive to the galaxy formation model that's adopted.
To be fair, that is absolutely not the way ΛCDM would have been described to someone in the pre-Webb days. It was a well-regarded theory and the hope was (a-la the Higgs detection) that new data would just better constrain the edges and get us on to the next phase of the problem.
But instead it's a wreck, and we didn't see what we were expecting at all, and so now we're retreating to "Well, ΛCDM wasn't exactly proven wrong, was it?!"
That doesn't mean it's wrong either, and it for sure doesn't mean MOND is right. But equally for sure this is a Kuhnian paradigm shift moment and I think it's important for the community to be willing to step back and entertain broader ideas.
Again, LCDM and galaxy formation are two different things. "...and we didn't see what we were expecting at all..." It depends on who you ask. There were many pre-JWST models that did well in this regard. A particularly interesting one is this from 2018 (https://ui.adsabs.harvard.edu/abs/2018MNRAS.474.2352C/abstra...). That group even had to write another paper reminding everyone of what they predicted (https://ui.adsabs.harvard.edu/abs/2024arXiv240602672L/abstra...). Another example is here (https://ui.adsabs.harvard.edu/abs/2023OJAp....6E..47M/abstra...) which shows results from a simulation from ~2014. I can provide numerous other examples of this. My point isn't which theory is or isn't wrong, my point is that what is presented in this particular article is not a constraint on any realistic theory of gravity as the sensitivity of these particular observations to galaxy formation modeling is so strong.
Absolutely not in the field, so if you are please completely disregard. But from conversations with physicists (not cosmologists) I always thought people thought a lot of evidence for ΛCDM was dubious at best.
> with JWST we see light and need to infer what the underlying properties of the system are
Every theory of dark matter is based exclusively on light-emitting objects. There is no "contrast" between JWST's methods and those of others. Casting aspersions on JWST because it can only see light is like casting aspersions on Galileo because he could only build telescopes. If we could teleport to the things we study and get more information that way, it would be nice, but we live in reality and must bend to its rules.
> highly sensitive to the galaxy formation model that's adopted
I should only need to remind the reader of the classic idiom "cart before the horse" to remind them that this line of reasoning is invalid.
This is a misrepresentation of what I am saying. By no means am I casting an aspersion on JWST. I am casting an aspersion on this particular observation as a test of MOND and LCDM. Also I highly disagree about your comments on my line of reasoning. The fact that you can obtain a huge range of possible galaxy properties in the context of LCDM indicates that in general, tests of LCDM and MOND that rely on galaxy formation model are in usually not strong tests. This is the key issue with using the abundance of high-z galaxies (or even their masses -- despite the fact that these aren't measured) as a test. In the context of LCDM, you need haloes to form galaxies but it has been shown many times that there are enough haloes to solve the problem (see the paper linked) by a huge amount.
And so you have proved my point. The observations presented in this article can be made consistent with both...as such one should think about stronger tests of both LCDM and MOND.
You are missing the point. JWST is not being singled out as different here, and no aspersions are being cast.
It is the entirely general point that all we can observe is the light, and we have to infer what that means. Maybe things are bright because there's a lot of stars. Maybe there aren't but there is not much dust. Maybe there aren't so many stars but they are bigger and brighter. There is room to fit many different models on the basis of the light that is observed.
I like this point a lot. But then I have to ask... why do I continuously encounter arguments that claim that the fundamental science of these scales is simply settled?
It feels like I read claims that dark matter is both a "given fact" and a "placeholder abstraction" -- from the same person, or at least perspective. They just choose to shift betweeen the two based on what serves their upper hand in a discussion better.
Or reading someone mention that "there is no fundamental difference between mass and energy" while simultaneously defending an entirely gravity-based cosmology that depends on the mass of particles... as if simple energy could not also contribute the same impact of said particles.
I think in general there is a feeling that any theory or speculation which is not dubbed into the dignity of mainstream, accepted dogma needs to be kicked out of the discourse. The fact that we are ultimately inferring in all cases is left out of the discussion and that seems to flatten all "outside" perspectives into a single umbrella of pseudoscience, despite this label accurately fitting -- under the above conditions -- onto heliocentrism, germ theory, chromosonal genetics, plate tectonics, the physical existence of Troy, and just about every paradigm that has resulted in scientific progress in the past.
I'm absolutely not claiming that all things currently labelled psuedoscientific are built the same. I only mean to highlight that science highlights "this is all inference" when it suits it best but otherwise -- in my experience -- discourages such frank reference to its own fallibility when confronted with alternative inferences.
In my experience this mostly occurs when people don't recognize names like Popper and Feierabend, and consider science and humanities to be mutually exclusive. Likely borne of a neurotic desire for certainty in all things. At least, that's my best guess having been steeped in the cultures of academia and industry for so long.
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.
The word "generation" isn't really a thing in astronomy jargon. "Population III" is a population, and it includes stars formed after some supernovae, up to the point where the metals % gets high enough to be Population II.
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.
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.
NB: based on some quick searches, it seems that low-metalicity Pop III stars would rely on the pp (proton-proton) fusion chain. That's going to slow reaction somewhat, and extend lifetime. But for high-mass stars with only a few millions of years expected lifetime in a Pop I/II class, that's ... still a relatively modest difference compared to the several hundred million year lifespan of the early Universe.
Another interesting quirk of Pop III stars is that their initial mass function is expected to form much more massive stars than Pop II or Pop I. So even if Pop III stars are longer lived at the same mass as Pop II or Pop I, there will be a lot more supernovae per time, leading to fast enrichment and then Pop II.
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.
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.
If I understand this correctly its like a mask between filters and the differential makes that differential much more noticeable? Wouldn't one of the challenges be that the pictures have to be almost the exact same time with those filters so that they line up perfectly to provide the differential given the high resolution?
Also thanks for the detailed response - their approach sounds like a smart solution minimizing unnecessary compute cost / algorithm scanning.
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.
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.
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.
Yea, but science fiction seems cooler when a story uses some plausible setting. In any case, another alternative is just to have a large planet with habitable moons in its orbit. Perhaps the planet itself is dead and too hostile for life, and the residents of the moons travel around it to get to civilizations on other moons.
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.
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.
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.
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!
Also, spectra don't vary significantly by isotope - even with deuterium the difference is fractions of a nanometer of wavelength, which is not something detectable in astronomical spectra.
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).
Hello! Author here (for real). Yes I didn't have much say in the headline but I'm fine with it, it's technically what the authors of the paper I covered were saying.
And thanks, hope you enjoyed the article! Regardless of whether this result stands up to scrutiny, I think this was a nice jumping off point to explain Pop III stars, and some of the interesting work JWST is doing here that people are probably not aware of (eg the programs mentioned at the end of the article).
> "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.
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.
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?
> 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.
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.
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).
Agreed, thanks for saying this. I'm also another astronomer by trade and I'm very surprised that Quanta ran with this title. I like the work that Xin Wang has done, and I'm usually a fan of Quanta Magazine reporting and Simons Foundation work -- I'm currently organizing a conference at the Flatiron Center for Computational Astrophysics -- but this is really lowering the bar for science journalism.!
This isn't literally an observation of a single star at that distance is it? If they only lasted a few million years then it will be unlikely to see a cluster of them devoid of other 2nd generation stars. It's doubtful (to me) that they all formed at the same time so as to not co-exist with other types.
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?
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"
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.
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?
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.
Same problem with categorizing star luminosity... I wish we could make a shift to these cumbersome categories, but cultural inertia is tough to overcome
So MOND does predict more galaxies at high redshift however it also predicts earlier reionization than LCDM which it turns out not to be true and the mass function of clusters is not what we see purely based on X-ray temperatures. So getting one thing right at the expense of many others doesn't make this particularly viable.
I have to say, this article is exceptionally disappointing. As someone who works in this space, there are numerous misleading depictions about the state of the field. Almost any respectable simulation shows that disk galaxies are widely present at very early times. This is simply an argument of angular momentum conservation and these rotational states are simply more transient at early times compared to the local Universe.
"Yan found 87 distant galaxies behind the galaxy cluster SMACS 0723" --> this is not true. They found 87 galaxy candidates. To be fair to the article, they do note that these await spectroscopic confirmation but experts only believe those with spectroscopic confirmation. Everything else is tentative and we don't yet have good numbers on confirmation rates. Finally, the Yan et al candidates are wildly inconsistent with almost every other estimate of high-redshift galaxy samples. You can see a comparison in Table 4 here: https://arxiv.org/pdf/2212.06683.pdf. They claim more than double the number of high-redshift sources compared to everyone else. JWST data is still very new and hard to both reduce and analyze. One particular problem is correlated hot pixels which can appear as very high-redshift sources. I don't know if this impacts the Yan et al paper but just an example of something that is not 100% straightforward to deal with. I highly recommend people take this with a healthy amount of skepticism until everything has a spectrum.
Honestly, thank you very much for this comment. As a lay person, I very often fall into taking such news as solid, as am kind of hoping for some great breakthroughs in cosmology (broadly speaking). Thanks for providing details. "One particular problem is correlated hot pixels" has a nice, cooling effect on me and I get the idea that it is an unsolved issue (kind of get it). Same with "experts only believe those with spectroscopic confirmation" - fair enough. An antidote for getting fooled in this way by such articles (or YT video beating some popular notions over and over) is to read core material (like books) and seek some actual lectures, I think. That's a pity you can't skim some topic and have it right. You just can't and it only fills you with fake knowledge.
The need of counterpoints and different views are important especially in academic field. But some debates got us lost as well. I would not say bad against YT but more about lack of quality one. Hope that will come.
Take an example of MONO discussed below. One claimed it is right but wrong in other prediction.
“ So MOND does predict more galaxies at high redshift however it also predicts earlier reionization than LCDM which it turns out not to be true and the mass function of clusters is not what we see purely based on X-ray temperatures. So getting one thing right at the expense of many others doesn't make this particularly viable.”
But the major discussion shifted to dark energy and refracted … and totally ignored that wrong predictions by mono … it is just hard to follow the threads.
