Astronomers Capture 13-Billion-Year-Old Signal From Universe's Dawn
Imagine listening to a sound that started its journey before our galaxy even existed. Astronomers are doing exactly that right now. They are picking up faint signals that have traveled for more than 13 billion years to finally reach Earth. These signals come from a time when the universe was still very young, long before the Milky Way took shape.
Reading the Universe's Earliest Diary
This discovery is like reading the universe's earliest diary pages. Scientists are not digging or studying fossils. Instead, they are examining very weak radio and microwave signals left behind after the Big Bang. The Milky Way formed billions of years after the Big Bang. However, some light and radio waves we detect today were emitted during the universe's first billion years. These signals have been traveling ever since, slowly stretched by the expansion of space, until they finally reached our telescopes.
In a rare achievement, astrophysicists from the CLASS project have detected a 13-billion-year-old microwave signal from the Cosmic Dawn. They used Earth-based telescopes located in the Andes mountains of Chile. The US National Science Foundation funded this research. The team is led by professor Tobias Marriage of Johns Hopkins University.
They captured faint polarised microwaves that reveal how the first cosmic structures influenced light left over from the Big Bang. This marks the first time such a signal has been detected from the ground. It defies earlier assumptions that only space telescopes could achieve this.
The Universe's Early Timeline
Right after the Big Bang, the universe was hot and dense. As it cooled, particles joined together to form neutral atoms. About 380,000 years later, light could finally move freely. This light still exists today as the cosmic microwave background.
After that came a long dark period. There were no stars, no galaxies, and no visible light. Scientists call this phase the Cosmic Dark Ages. Between about 50 million and one billion years after the Big Bang, the first stars and galaxies began to form. Researchers call this period the Cosmic Dawn.
Signals from this time are especially valuable. They show how the universe moved from darkness to light. Known as Population III stars, the early stars were massive. They were composed almost entirely of hydrogen and helium. These stars burned out quickly. Their ultraviolet radiation ionised surrounding hydrogen gas. This allowed light to travel freely and marked the universe's transition from darkness to light.
"It's one of the most unexplored periods in our universe," a research scientist at the International Centre for Radio Astronomy Research in Perth, Australia, told Live Science. "There's just so much to learn."
The Signal Scientists Are Chasing
One of the most important clues from the early universe comes from hydrogen. Hydrogen filled most of space after the Big Bang. Neutral hydrogen naturally produces a weak radio signal known as the 21-centimetre line. By tracking this signal, scientists can learn how hydrogen behaved billions of years ago. They can also understand how the first stars and black holes affected it.
As the universe expanded, this signal stretched to longer wavelengths. Its polarisation means the waves align in specific directions. This can reveal the distribution and motion of early matter. It provides a map of the universe's large-scale structure. Polarisation is a key tool for understanding cosmic evolution.
Unlike light from distant galaxies, which can be very hard to see, the hydrogen signal tells a bigger story. It shows what was happening across huge regions of space, not just where bright objects existed. These ancient microwaves are not only faint but also polarised. Their waves align in specific directions due to interactions with early matter.
Detecting them from Earth is extremely challenging. They are easily drowned out by terrestrial radio noise, satellites, and atmospheric conditions. The CLASS team overcame these challenges. They used high-altitude sites in Chile. They cross-referenced their data with space missions like Nasa's WMAP and ESA's Planck. They carefully filtered interference to isolate the genuine cosmic signal.
Projects like REACH and the future Square Kilometre Array are designed to expand these observations. They aim to detect similar signals across the universe. When the first stars switched on, they gave off ultraviolet and X-ray radiation. This changed how hydrogen behaved. Those changes are recorded in the 21-centimetre signal.
By studying its strength and pattern, scientists can work out when the first stars formed. They can also determine how powerful these stars were.
How Astronomers Detect Old Signals
Telescopes like the James Webb Space Telescope look for light from early galaxies. But for these ancient hydrogen signals, scientists rely on radio telescopes. Radio observations complement optical and infrared studies. While JWST shows the actual galaxies and stars forming, radio signals reveal the state of the surrounding gas and large-scale structures.
Together, they give a fuller picture of the early universe. These ancient signals are extremely weak. They are easily buried under radio noise from Earth, satellites, and our own galaxy. That is why scientists need very sensitive instruments and remote locations. Future observatories may even be placed on the Moon, where Earth's interference is blocked.
JWST has already found surprisingly mature and chaotic galaxies from the universe's early years. Combining JWST data with radio measurements allows scientists to understand both the environments and the galaxies themselves.
What a 13-Billion-Year-Old Signal Reveals
Recent observations from ground-based telescopes in Chile have picked up signals dating back around 13 billion years. These signals suggest that hydrogen gas was already being affected by energetic radiation during the Cosmic Dawn. This shows that stars influenced their surroundings much earlier than previously thought.
By examining polarisation and 21-cm signal patterns, researchers can estimate star formation rates, star sizes, and the intensity of early starlight. The earliest stars were not like the ones we see today. They formed from hydrogen and helium, with almost no heavier elements. Scientists believe these stars were very large and burned out quickly.
Observations also indicate that early galaxies formed faster and were more chaotic than expected. This challenges older ideas about gradual structure formation. It raises questions about how matter clumped together so quickly.
What Comes Next in the Search for Cosmic Origins
Despite new discoveries, many things remain unclear. Scientists still want to know exactly when the first stars formed. They aim to understand how massive these stars were and how quickly galaxies grew. Researchers also want to learn how early black holes shaped their surroundings and the intergalactic medium.
Future instruments like SKA, REACH, and Moon-based observatories may finally resolve these mysteries. Learning about the universe's first billion years helps scientists understand how everything came to be. It informs theories about matter, energy, and the forces that shape the cosmos.
Even though we cannot travel back in time, these ancient signals allow us to read the universe's earliest chapters. By examining polarised microwaves, scientists trace how early stars and galaxies influenced their surroundings. They study how these structures shaped large-scale cosmic formations and laid the foundations for modern galaxies.
Ground-based technology is now enabling discoveries that once only space telescopes could achieve. Detecting signals older than the Milky Way is altering our understanding of cosmic history. By combining radio observations with powerful optical telescopes, scientists are slowly building a clearer picture of the universe's earliest days.
Each new signal adds another piece to the story. It tells us how darkness gave way to light and how the universe we live in today first began to take shape. The next decades promise even more revelations about the Cosmic Dawn, its stars, galaxies, and the origins of the cosmos itself.
