What are Population III stars? In short, the alleged story is as follows:
The super-hot big bang fireball produced only hydrogen (~75%), helium (~25%) and tiny traces of lithium. So the first stars to form (given the name Population III stars) could only form from these gases. Astronomers label all elements heavier than helium as ‘metals.’ Thus they call these type of stars extremely metal-poor. But each successive generation of stars, being formed from the products of supernova explosions of the generation of stars before them, which produced all the heavier elements, became more and more metal rich. The nuclear fusion within stars during their life produced the heavier elements, the ‘metals,’ like carbon, oxygen, and nitrogen, which were released into space when the stars exploded. During the actual explosion it is theorized that the very heaviest elements were produced also. Population III stars allegedly were the first stars formed just shortly after the big bang.
Until now (as claimed) these original stars have never be observed, hence they were nothing more than hypothetical. But their existence is a big bang prediction.
Population I, II and III stars
Astronomers classify stars into three types: Population I, II and III. Population II are those generation of stars, which allegedly formed from the Population III stars and have only a low metal content. Population I stars were allegedly the last to form, hence are the youngest and hottest stars and those with high metal content. Population I and II stars were historically first identified in our Galaxy. Population I stars are found predominantly in the spiral disk of the Galaxy and Population II stars are found above and below the disk. They have other distinguishing features also but their metal content is the major distinguishing feature.
Those early-generation stars also first formed into small galaxies that later by merging with other galaxies grew larger, or so the story goes.1 Growth in galaxy size and in ‘metal’ content is called ‘galaxy evolution.’
The first generation of small galaxies was likely well in place 400 million years after the Big Bang. Following this initial phase of galaxy formation, galaxies then went through an extended phase of merging and coalescence with other galaxies, whereby they built up from masses of several thousand solar masses to billions of solar masses. This buildup process extended until the universe was roughly two billion years old. Then, due to some feedback process — now predominantly speculated to be AGN feedback — it is thought that this buildup process halted and gas accretion and star formation in the most massive galaxies halted and galaxies underwent a much different form of evolution. This later evolution continues to the present day.
This is the big bang evolution story, but it vitally needs those Population III stars or there is no story. Now it is claimed that Population III have been found in a very distant galaxy.
What was found?
A National Geographic online article reported:2
Peering to the edge of the visible cosmos with some of the most powerful telescopes on the planet, astronomers have detected light from the very first generation of stars to emerge after the big bang.
In a galaxy named CR7 they claimed to have detected the presence of Population III stars, but note the following. The distance is determined from the redshift of the galaxy, which is why the reporter writes that it is as on “the edge of the visible cosmos”. But if the redshift interpretation for those very high redshift galaxies is not correct (an unverifiable assumption) then the galaxy is not so distant, nor so large nor so bright as claimed.
“The evidence is convincing,” says Harvard astrophysicist Avi Loeb, one of the theorists who predicted what first-generation stars should look like. “It provides the strongest observational evidence to date for the stars made out of pristine hydrogen and helium, left over from the big bang.”2
Of course the theorist who predicted this would want it to be true. But no detection of a single star was made. Instead, they captured the collective light of stars in the galaxy CR7. They then claimed, based on redshift (z = 6.6) and their assumed cosmology, that the stars in this galaxy are seen at a time 800 million years after the big bang.3
CR7 also has clumps of stars that are not from the first generation. This is consistent with theoretical predictions, Loeb notes. Modern galaxies, including the Milky Way, are thought to have assembled themselves from much smaller proto-galaxies that began forming a few hundred million years after the big bang. CR7 is probably a snapshot of the early stages of that process, in which some parts have recently formed their very first stars while others have already moved on to the second generation.2 (my emphases added)
It is admitted, that the galaxy does not contain only Population III stars. Thus it contains Population II and/or Population I stars, which have much higher metal content. This is probably due to the fact that if a spectrograph was used to detect metals it would see light from the whole galaxy or a large part of it. But they seem to base their arguments largely on the excess of light, meaning the galaxy is very bright for its redshift. Very bright means large hot stars, and large stars means they might be Population III stars.
This is story telling. Whatever is observed can be fitted into the story. The story (as quoted above) allows for mergers and accumulation of mass in smaller first generation galaxies, which allows for the observation of a mixture of types, some with much, some with little and some with no metal content. Then the astronomer can use the observed brightness of the galaxy—which depends on its redshift and assumed cosmology—and whatever metal content they do observe to fit any such candidate galaxy into the story. It is very flexible. If it has more metal, it has evolved more than one which has very little metal.
Evidence to consider
I was recently presented with an argument that there was a systematic trend of decreasing metal content of stars/galaxies as a function of increasing redshift.4 Older galaxies should have higher redshifts and less metals in their constituent stars. How does that fit into any creationist cosmology? It was suggested that the trend is what the big bang expects and in contradiction to creationist cosmologies. But the latter argument hangs on the validity of the source’s redshift as both distance and time indicators. If, as Halton Arp strongly promoted in his lifetime,5-7 there is a component of redshift that is intrinsic to quasars and active galaxy nuclei (AGNs), then their measured redshifts are not a reliable distance indicator, nor can they tell you how young or how evolved the quasars/galaxies might be, as is alleged. This then undermines the alleged trend of lower metallicity at higher redshift, and hence in the ‘oldest’ generation stars. Oldest here means the ones that allegedly formed first after the big bang.
I would make the point that the assumed ‘youth’ of a galaxy, hence how massive it is at a certain epoch of its life, depends critically on accurately knowing ‘when’ it is you are seeing it. But that then depends strongly on the meaning of galaxy redshifts and on any assumed cosmological model. At very high redshifts, to fit galaxies into the trend of metallicity verses redshift, a tuning knob called ‘galaxy evolution’ is used. This is used to make any observation fit into the overall story.8 It provides the needed flexibility.
A Hubble-like law could still apply in a static universe, for example, but only for a component of the total redshift of a galaxy. It would not be from expansion but something else. I have suggested it could be due to ‘tired light,’ which Edwin Hubble considered himself.9 So a large intrinsic redshift could have several components to it, where only a small fraction is due to some Hubble law-like distance relationship. The main problem though is how to separate out the Hubble law-like component.4
Now to answer the headline question: Have Population III stars finally been discovered? No, they haven’t. It is just more big-bang story telling. They would need to identify some stars containing no metals, which according to standard cosmology are located in galaxies that are less than 400 million years old, and hence with measured redshifts of order 12 or greater (and that is granting the validity of the distance/redshift assumptions).
Galaxy formation allegedly started at the beginning of the era of Reionization (dotted line labelled Hubble 2012 in Fig. 2). The first stars allegedly formed before that at a redshift of 20 or greater. The period of most galaxy formation followed that, as the story goes, between the time when galaxies had a redshift (z) of about 12 and lasted until the time when their redshift was about 8 as shown in Fig. 2 (between the dotted lines).8 That corresponds to between 300 and 700 million years after the big bang.
But even then if they did find an example of a galaxy of stars with zero metals, or a group of stars with zero metals, it still would not prove the big bang, because it may be evidence of a prediction in favour of the big bang but it is not sufficient (the fallacy of affirming the consequent). You would have to prove no other model could account for it.
The biblical creation account predicts a creation scenario with various galaxy/star types. They didn’t all start out as embryonic blobs of plasma. God made fully formed stars. After all, the “heavens declare [are telling of] the glory of God, and the firmament [expanse, cosmos] shows His handiwork.” (Psalm 19:1)
- The Beginning of the Universe, firstgalaxies.org.
- M.D. Lemonick, Astronomers Glimpse Very First Stars in the Universe, National Geographic, June 17, 2015.
- This discovery will soon be published in the leading astrophysics journal the Astrophysical Journal, PDF preprint http://arxiv.org/pdf/1504.01734v2.pdf.
- J.G. Hartnett, On metal abundances verses redshift in creationist cosmologies, October 20, 2015.
- J.G. Hartnett, Galaxy-quasar associations, January 1, 2014.
- J.G. Hartnett, What do quasars tell us about the universe? May 10, 2014.
- J.G. Hartnett, Big-bang-defying giant of astronomy passes away, December 31, 2013.
- J.G. Hartnett, Is there definitive evidence for an expanding universe? August 19, 2014.
- J.G. Hartnett, Speculation on redshift in a created universe, February 13, 2015.