In the summer of 2022, astronomers shared their findings from the first observations of very distant (and therefore very young) galaxies by the James Webb Space Telescope (JWST). As reported by Evolution News at the time (here, here, here), they expressed their great surprise at finding so many mature looking, yet very young, galaxies. A long-time critic of the Big Bang theory, Eric Lerner, took the opportunity to claim that these new data disprove it.
As Stephen Meyer pointed out in September 2022 (here), even if the initial JWST observations were taken at face value and showed that galaxy formation did not agree with predictions, it would not disprove the Big Bang theory. It would just show that theories of galaxy formation need revision. This is because the Big Bang theory rests on three observational pillars: the cosmic microwave background radiation, the abundances of the light element (H, He, Li) isotopes, and the Hubble-Lemaître redshift-distance law. For details about these observations and their historical context see my two Evolution News posts (here, here). At most, observations of early galaxy formation offer only a weak test of the Big Bang theory.
Learning to Be Patient
I’ve learned to be patient about making too much of the very latest scientific discoveries. “Let the dust settle,” I say. These are the most distant galaxies astronomers have seen, and these were among the first observations they made with the JWST. Astronomers must be sure that they properly calibrate the data and account for the relevant biases statistically. All this is very tedious and takes time. Another possible concern is that the early JWST galaxy redshifts were based on photometry using filters. This method is not as reliable as spectroscopy, but it is easier to do. As spectroscopic redshifts continue to trickle in, the results are placed on a more secure footing.
The Needed Bookkeeping
Well, it looks like some astronomers have done the needed bookkeeping. One study compared a suite of cosmological simulations to the JWST observations of distant galaxies.1 They found that standard early galaxy growth models can explain the JWST observations without invoking nonstandard cosmology or ad hoc fine-tuning of models. In particular, their simulations show that bursty star formation needs to be taken into account in these early times, rather than a smoothly varying one. Neglecting it can lead to biases in estimating the number of bright galaxies in early times.
Another recent study (not yet peer reviewed) concluded that early JWST observations of distant seemingly massive and mature galaxies were misinterpreted.2 The galaxies they studied were selected according to a certain spectral feature called a double-break (highly redshifted Lyman and Balmer breaks). For five of the galaxies, the colors were due to emission lines in star-forming galaxies which caused them to be misclassified as massive double break galaxies. They observed more galaxies and over multiple fields than the early studies, giving them a much better handle on the statistics. The field-to-field cosmic variations can cause the maximum mass to be vastly overestimated. They conclude that the double-break galaxies they surveyed do not contradict standard cosmology.
While they haven’t received much attention, a couple other recent studies provide a clean and simple test of the Big Bang theory. One of them3 determined the age of an ancient star cluster. Clearly, to be consistent with the Big Bang theory the ages of the oldest stars cannot exceed the cosmological age. To date, observations of the cosmic microwave background radiation have yielded the most accurate and precise cosmological age (13.80 ± 0.06 billion years).
M92 is one of about 160 known globular star clusters in the Milky Way galaxy and is estimated to contain about 330,000 stars. Given its proximity, astronomers have been studying it for over a century, each decade bringing to bear better observation tools and/or better models. This latest study yielded an age of 13.80 ± 0.75 billion years and determined that the observations are consistent with the stars in the cluster having formed nearly simultaneously. To date, this is the most accurate and precise determination of age for a group of coeval stars. Within the quoted error, M92 formed up to 0.75 billion years after the Big Bang, which is enough time for M92 to have formed according to standard cosmology. If M92 were found to be, say, 16.5 ± 0.75 billion years, then that would pose a major challenge to the Big Bang theory.
The Best Age Determinations
A recent study4 summarizes the best age determinations greater than 13.3 billion years (see their Table 2). What is telling is their consistency, despite the very different methods employed. These include individual stars, globular clusters, ultrafaint galaxies in the Local Group, nucleochronometry (uranium and thorium abundances), and the white dwarf cooling time. None of the values are in clear contradiction of the age derived from the microwave background. The current record holder for the oldest individual star is HD 140283. The study cited by Cimatti and Moresco from 2013 (second to last value in their Table 2) gives it an age of 14.46 ± 0.8 billion years. However, a more recent study5, using a more accurate GAIA spacecraft parallax (to get the distance), confirms its age is near 14 billion years. However, they don’t give a precise age or errors.
In summary, the Big Bang theory has passed a strong test and a weak one. That’s not to say there are no tensions between theory and observation. There are, and that’s what makes cosmology so interesting.
- G. Sun, et al., “Bursty Star Formation Naturally Explains the Abundance of Bright Galaxies at Cosmic Dawn,” The Astrophysical Journal Letters 955 (2023): L35.
- G. Desprez et al., “LCDM Not Dead Yet: Massive High-z Balmer Break Galaxies are Less Common than Previously Reported,” Monthly Notices of the Royal Astronomical Society, submitted (October 2023).
- J. Ying, et al., “The Absolute Age of M92,” The Astronomical Journal 166 (2023): 18
- A. Cimatti and M. Moresco, “Revisiting Oldest Stars as Cosmological Probes: New Constraints on the Hubble Constant,” The Astrophysical Journal 953 (2023): 149
- M. Spite, et al., “12C/13C Ratio and CNO Abundances in the Classical Very Old Metal-poor Dwarf HD 140283,” Astronomy & Astrophysics 652 (2021): A97