The James Webb Space Telescope discovers enormous distant galaxies that should not exist

Six distant galaxies discovered in early James Webb Space Telescope images appear surprisingly large for their age.
These six galaxies may force astronomers to rewrite cosmology books. (Image credit: NASA, ESA, CSA, I. LABBE)

Nobody expected them. They were not supposed to be there. And now, nobody can explain how they had formed. 

Galaxies nearly as massive as the Milky Way and full of mature red stars seem to be dispersed in deep field images obtained by the James Webb Space Telescope (Webb or JWST)  during its early observation campaign, and they are giving astronomers a headache. 

These galaxies, described in a new study based on Webb's  first data release, are so far away that they appear only as tiny reddish dots to the powerful telescope. By analyzing the light emitted by these galaxies, astronomers established that they were viewing them in our universe's infancy only 500 to 700 million years after the Big Bang.

Such early galaxies are not in themselves surprising. Astronomers expected that first star clusters sprung up shortly after the universe moved out of the so-called dark ages — the first 400 million years of its existence when only a thick fog of hydrogen atoms permeated space. 

Related: 12 amazing James Webb Space Telescope discoveries across the universe

But the galaxies found in the Webb images appeared shockingly big, and the stars in them too old. The new findings are in conflict with existing ideas of how the universe looked and evolved in its early years, and don't match earlier observations made by Webb's less powerful predecessor, the Hubble Space Telescope.

"We had specific expectations for the type of galaxies that live in the early universe: they are young and small," Joel Leja, assistant professor of astronomy and astrophysics at Penn State and one of the authors of the study, told in an email. "Previous studies of the early universe with Hubble and other instruments tend to find small, blue, baby galaxies at early times: objects which have just recently formed out of the primordial cosmic soup and are themselves building their early stars and structures."

Young stars in general shine bright blue. With age, stars develop a redder glow as they burn through their fuel and cool down. In ancient galaxies that Webb was built to spot, astronomers had not expected to see old red stars. They also had not expected to find galaxies more massive than perhaps a billion suns. But those reddish dots revealed in Webb's deep fields appear 50 times more massive than that, Leja said. 

"The most massive galaxies in our sample are estimated to have masses [two to four times lower] than that of our own Milky Way," Leja wrote. "This was astounding — we're finding galaxy candidates as massive as our own galaxy when the universe was 3% of its current age."

Leja said that before astronomers start rewriting cosmology theories to explain how these galaxies came together so quickly after the Big Bang, they will have to ensure the odd red dots they are looking at are not something else. Most of the alternative explanations, however, also require entirely new concepts, Leja said. 

"For example, stars in the early universe might emit light in exotic ways due to their lack of heavy elements, and perhaps we're not incorporating those in our models," Leja wrote. "Or alternatively, perhaps our understanding of how stars form locally, e.g. how many stars form from gas as a function of the mass of the stars, is totally inapplicable in the early universe. These things would also be exciting to discover and would also overturn our understanding of star formation in the early universe — just in a very different way."

The images that revealed these puzzling galaxies were obtained by Webb's Near Infrared Camera (NIRCam) as part of the Cosmic Evolution Early Release Science (CEERS) program. Astronomers plan to soon turn Webb's mirror to these galaxies again to, this time, obtain light spectra of those distant dots. Spectra break down the observed light according to its wavelength composition and thus reveal the chemical and physical properties of its source. 

"The most important thing is that spectra give very precise distances to these objects," said Leja. "The "distance" and the "identity" of these objects is correlated: if we know the distance, we can pin down the identity, and vice versa. So a spectrum will pretty immediately tell us if our hypotheses are correct."

Only a little more than six months after the Webb team released the first observations from the grand observatory, scientists are already challenged to rewrite their theories about the early universe.

"We looked into the very early universe for the first time and had no idea what we were going to find," Leja said in a Penn University statement. "It turns out we found something so unexpected it actually creates problems for science. It calls the whole picture of early galaxy formation into question."

The study was published in the journal Nature on Wednesday (Feb. 22). 

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Tereza Pultarova
Senior Writer

Tereza is a London-based science and technology journalist, aspiring fiction writer and amateur gymnast. Originally from Prague, the Czech Republic, she spent the first seven years of her career working as a reporter, script-writer and presenter for various TV programmes of the Czech Public Service Television. She later took a career break to pursue further education and added a Master's in Science from the International Space University, France, to her Bachelor's in Journalism and Master's in Cultural Anthropology from Prague's Charles University. She worked as a reporter at the Engineering and Technology magazine, freelanced for a range of publications including Live Science,, Professional Engineering, Via Satellite and Space News and served as a maternity cover science editor at the European Space Agency.

  • rod
    Same issues here as I discussed in post #61 above. The only objective way to verify galaxy evolution models is to compare their present dimensions at their look back time distance (what we see on Earth and redshift) with what they look like at the comoving radial distances (not observable from Earth) because of the immense distances in the BB model for expansion. Something like the Sparkler galaxy in post #61 is a good example.
  • Atliberty
    The cosmic egg exploding at the moment of creation theory known as the big bang will fade into history like the flat Earth geocentric theory and give way to an infinite universe theory.
  • Sabo
    Gosh, and here I was simply pointing out that the writer apparently didn't bother to read the published article she's reporting on... There's a big difference between "500,000 to 700,000 years" (which she had to conscientiously type out), and 500 to 700 MILLION years after the 'Big Bang'.

    Understand how, as a new reader, I might become immediately skeptical of a publication's quality when their writers fail to pay attention to critically significant numbers involving the discussion.

    Just saying...
  • Decarboxylate
    Atliberty said:
    The cosmic egg exploding at the moment of creation theory known as the big bang will fade into history like the flat Earth geocentric theory and give way to an infinite universe theory.

    Absolutely. But this will take a lot of time. The hubris of modern scientists (I'm looking at you Neil DeGrasse Tyson) is astonishing. They forget that every generation of scientists before also thought they had it figured out for sure.
  • Decarboxylate
    Flat Earth gave way to...

    Geocentric Universe which gave way to...

    Heliocentric Universe which gave way to...

    One Galaxy gave way to...

    Accelerating Expansion of a finite universe will give way to...

    Point is, there's no reason to think the Big Bang Theory is the end all. We still know almost nothing and we need to be ready for the next paradigm... Whatever that may be.
  • murgatroyd
    What difference does it make whether or not the universe is infinite? We cannot interact with nor even observe what lies outside of the observable universe, so why bother?
  • billslugg
    When you get out past the edge of the observable universe the Dollar Stores really start thinning out.
  • mikekrumm
    How do we know we're not looking at our own stellar neighborhood in a looped universe?
  • rod
    The reference cited in the article, ref - A population of red candidate massive galaxies ~600 Myr after the Big Bang,, 22-Feb-2023. "Abstract Galaxies with stellar masses as high as ~ 10^11 solar masses have been identified1–3 out to redshifts z ~ 6, approximately one billion years after the Big Bang. It has been difficult to find massive galaxies at even earlier times, as the Balmer break region, which is needed for accurate mass estimates, is redshifted to wavelengths beyond 2.5 μm. Here we make use of the 1-5 μm coverage of the JWST early release observations to search for intrinsically red galaxies in the first ≈ 750 million years of cosmic history. In the survey area, we find six candidate massive galaxies (stellar mass > 10^10 solar masses) at 7.4 ≤ z ≤ 9.1, 500–700 Myr after the Big Bang, including one galaxy with a possible stellar mass of ~10^11 solar masses. If verified with spectroscopy, the stellar mass density in massive galaxies would be much higher than anticipated from previous studies based on rest-frame ultraviolet-selected samples."

    My observation. can be used to show calculations, z=9.1 light-time or look back distance is 13.178 Gyr or 13.178 billion light-years from Earth. The age of the universe at z=9.1 is 0.543 Gyr and comoving radial distance is 30.802 Gly. Using H0=69 km/s/Mpc space is expanding 2.1735932 x c velocity at the comoving radial distance. Any galaxies seen by JWST with such deep or large redshifts, presently sit in the universe immensely farther away and evolved into what? Unknown morphology and mass evolutionary changes it seems when comparing the look back distance with comoving radial distances in the expanding universe model. Little mysteries like this appear when you dive deeper into BB cosmology and redshift interpretations.
  • karlp295
    All this speculation and in time we will develop new theories that get closer to reality, whatever that is. We are always mostly wrong and it is normal that theories will change. One day I am hopeful that we will begin to understand about creation which we know nothing about at present.