Early Star Formation May Have Impacted Cosmic Microwave Background

Early Star Formation May Have Impacted Cosmic Microwave Background
by Robert Schreiber
Berlin, Germany (SPX) May 13, 2025

The afterglow of the universe, known as the cosmic microwave background (CMB), provides critical insights into the early cosmos and the formation of the first galaxies. However, researchers from the Universities of Bonn, Prague, and Nanjing have presented calculations suggesting that this radiation's strength may have been significantly overestimated. If validated, their findings could challenge the standard model of cosmology, potentially reshaping our understanding of the universe's origins.

The Big Bang, which occurred approximately 13.8 billion years ago, marked the origin of the universe. In the first 380,000 years, the cosmos rapidly expanded and cooled, allowing protons and electrons to combine into neutral hydrogen atoms. This event, known as recombination, enabled light to travel freely for the first time, forming the CMB.

However, recent studies indicate that part of this radiation may not be as ancient as previously thought. According to Prof. Dr. Pavel Kroupa from the Helmholtz Institute for Radiation and Nuclear Physics at the University of Bonn and Charles University in Prague, some of the CMB might actually originate from intense star formation in early elliptical galaxies. "Our calculations indicate that some of the cosmic background radiation actually originates from the formation of the elliptical galaxies," says Kroupa. "This accounts for at least 1.4 percent of the radiation but could even account for all of it."

Elliptical galaxies, among the first to form after the Big Bang, condensed vast amounts of gas into hundreds of billions of stars within a relatively short time. Dr. Eda Gjergo of the University of Nanjing emphasized that this early "star fire" would have been exceptionally luminous, potentially contributing significantly to the CMB. If this contribution is confirmed, it could cast doubt on decades of cosmological measurements that rely on the CMB's presumed uniformity.

Researchers have long interpreted subtle variations in the CMB as evidence of slight density fluctuations in the early universe, which allowed gas to collapse into galaxies. However, if even a small portion of this radiation comes from a more recent source, the reliability of these measurements could be called into question. "It might be necessary to rewrite the history of the universe, at least in part," added Kroupa.

Research Report:The Impact of Early Massive Galaxy Formation on the Cosmic Microwave Background