Breakthrough Discovery: 13-Billion-Year-Old Cosmic Dawn Signal Detected

In a remarkable scientific achievement, researchers from the CLASS (Cosmology Large Angular Scale Surveyor) project have successfully captured a 13-billion-year-old microwave signal, originating from the Cosmic Dawn, using ground-based telescopes in the Andes mountains of northern Chile. This groundbreaking discovery, announced on June 15, 2025, represents a significant leap in our understanding of the early universe and the formation of its first stars and galaxies.

The Cosmic Dawn refers to a pivotal period in cosmic history, occurring between approximately 50 million and one billion years after the Big Bang. During this era, the universe transitioned from a dark, neutral state to one filled with light as the first stars ignited nuclear fusion, emitting intense ultraviolet radiation. This radiation not only illuminated the universe but also initiated the process of reionization, allowing light to travel freely through space for the first time. The CLASS project, funded by the U.S. National Science Foundation, aims to study these early cosmic structures by analyzing the faint signals they left behind.

According to Professor Tobias Marriage, an astrophysicist at Johns Hopkins University and the lead investigator of the CLASS project, detecting such ancient signals from the ground had previously been deemed impossible due to the numerous technological and environmental challenges involved. “People thought this couldn’t be done from the ground,” stated Marriage. “Astronomy is a technology-limited field, and microwave signals from the Cosmic Dawn are famously difficult to measure.”

The microwaves associated with the Cosmic Dawn are extraordinarily faint, approximately one million times weaker than the regular cosmic microwave background radiation. Ground-based observations face significant interference from various sources, including radio broadcasts, radar signals, and atmospheric conditions, making detection a formidable task.

To overcome these challenges, the CLASS team employed custom-designed telescopes strategically placed in high-altitude regions of Chile, where the thinner atmosphere reduces interference. They meticulously cross-referenced their data with previous observations from space missions, such as NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency’s Planck telescope, to isolate the authentic signals from the noise.

The implications of this discovery are profound. The ability to study these microwave signals allows scientists to trace the formation and evolution of the universe's earliest structures. As Dr. Yunyang Li, a co-author of the study and a researcher at Johns Hopkins University and the University of Chicago, explained, “Using the new common signal, we can determine how much of what we’re seeing is cosmic glare from light bouncing off the hood of the cosmic dawn.” This research opens new avenues for exploring the origins of the universe without solely relying on space-based telescopes.

Historically, observations of the Cosmic Dawn have primarily relied on data collected from space, leading to a limited understanding of this formative period. The CLASS project’s findings not only validate the capabilities of ground-based astronomy but also pave the way for deeper investigations into the birth of stars and the formation of galaxies.

As scientists continue to analyze the implications of this discovery, the CLASS project serves as a testament to the potential of advanced ground-based technology combined with innovative methodologies. The insights gained from the Cosmic Dawn signal could fundamentally reshape our understanding of the universe’s history and evolution, marking a new chapter in cosmological research.

In conclusion, this breakthrough signifies a notable advancement in astrophysics, affirming the viability of ground-based observations in unraveling the mysteries of the universe's earliest epochs. Future studies will likely build upon this foundation, offering unprecedented insights into the interactions between early light sources and cosmic matter, ultimately enhancing our comprehension of how galaxies, including our own Milky Way, came to be.