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In a study published in Nature Astronomy, Mike Boylan-Kolchin, assistant professor of astronomy at the University of Texas at Austin, finds that six of the oldest and largest candidate galaxies Webb has spotted so far contradict mainstream thinking in cosmology.
This is because other researchers estimate that each galaxy appears to be 500 million to 700 million years after the Big Bang, but measures more than 10 billion times the mass of our Sun. Even one of the galaxies appears larger than the Milky Way, despite the fact that our galaxy has billions of years to form and grow.
“If the masses are right, we are in uncharted territory,” Boylan-Kolchin said in a statement. “We would need something very new about galaxy formation or tweaking the cosmology. One of the more extreme possibilities is that the universe was expanding faster soon after the Big Bang than we expect, which would require new forces and particles.” “.
In order for galaxies to form so quickly and to this size, they would also have to convert nearly 100% of their available gas into stars.
“We usually see no more than 10% of the gas turning into stars,” Boylan-Kolchin said. “So while converting 100% of gas into stars is technically on the edge of what is theoretically possible, in reality this requires something very different from what we expect.”
Webb presented a troubling dilemma for astronomers. If the masses and time since the Big Bang of these galaxies are confirmed, fundamental changes may be necessary to the dominant paradigm in cosmology, the so-called dark energy + cold dark matter model, which has guided cosmology since the late 1990s. If there are other, faster ways of forming galaxies than the paradigm allows, or if there really is more material available to form stars and galaxies in the early universe than previously thought, astronomers will have to change its prevailing thinking.
The times and masses of the six galaxies are preliminary estimates and will need to be confirmed with follow-up using spectroscopy, a method that divides light into a spectrum and analyzes the brightness of different colors. Such an analysis could suggest that central supermassive black holes, which can heat surrounding gas, may make galaxies brighter to make them appear more massive than they really are. Or perhaps the galaxies were actually seen much later than originally expected due to the dust making the color of the galaxy’s light redder, giving the illusion that they are light years away and thus going back in time.
The galaxy data came from the Cosmic Evolution Early Release Science Survey (CEERS), a multi-institutional JWST initiative led by UT Austin astronomer Steven Finkelstein.
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