A recent study by researchers from the Universities of Bonn, Prague, and Nanjing suggests that some of the cosmic microwave background (CMB) radiation—the faint glow left over from the Big Bang—may come from a different source than previously thought. If confirmed, this finding could challenge the standard model of cosmology. The study, published in Nuclear Physics B, points to the formation of massive early-type galaxies (ETGs) as a previously overlooked contributor to the CMB signal.
The CMB has long been used to study the early universe, as it is thought to be a remnant of the first few hundred thousand years after the Big Bang. However, this new research suggests that a part of the radiation may actually come from the formation of ETGs—large galaxies that formed very early in cosmic history.
“The universe has been expanding since the Big Bang, like dough that is rising,” explains Professor Pavel Kroupa from the University of Bonn and Charles University in Prague. “This means that the distance between galaxies is increasing constantly.”
Dr. Eda Gjergo from the University of Nanjing adds that ETGs likely formed very quickly, accumulating huge amounts of gas that ignited intense star formation. These stars burned incredibly bright, producing radiation that could still be detected today.
For decades, scientists have debated how massive galaxies formed in the early universe. Some believed they grew slowly over time, but recent discoveries—including observations from the James Webb Space Telescope (JWST)—suggest they came together much faster. Chemical evolution studies also support this idea, showing that the stars in these galaxies must have formed under extreme conditions.
The researchers estimate that each ETG began as a huge gas cloud around 400 kiloparsecs in size. Based on their spacing in the universe today, they likely formed at redshifts between 15 and 20. The study models their formation within the standard cosmological framework (flat-ΛCDM), incorporating known features of ETGs that align with the integrated galaxy-wide IMF (IGIMF) theory.
The surprising part? These galaxies could be responsible for at least 1.4%—and possibly all—of the CMB radiation measured today. If even a small fraction of this radiation comes from galaxies rather than the Big Bang, previous estimates of the universe’s structure and evolution might need to be reevaluated.
The CMB is used to study the early distribution of matter and understand how galaxies formed. Scientists have assumed that tiny variations in its intensity reflect differences in gas density in the young universe, which helped galaxies take shape. But if ETGs contribute to this radiation, these calculations might not be as precise as previously thought.
“Our results are a problem for the standard model of cosmology,” Kroupa states. “It might be necessary to rewrite the history of the universe, at least in part.”
While more research is needed to confirm these findings, this study raises important questions about how much we really understand about the early universe and its origins.
Source: University of Bonn, ScienceDirect
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