Cosmic dawn observed through ground-based telescopes provides a new perspective
In an awe-inspiring moment, scientists have cracked the code on the cosmic dawn, taking Earth-based telescopes back over 13 billion years to witness how the first stars in the universe distorted light from the big bang.
Rising high in the Andes mountains of northern Chile, the ingenious telescopes were able to detect this polarized microwave light, painting a clearer picture of a time period that remains one of the most mysterious chapters in the history of the universe, known as the cosmic dawn.
"People whispered that this couldn't be done from the ground. Astronomy is a field held back by technology, and microwave signals from the cosmic dawn are notoriously tricky to catch," said project leader, Tobias Marriage, a professor of physics and astronomy at Johns Hopkins University. "Beating the odds and measuring these signals from the ground is a massive achievement."
Insights:
- Early star formation during the cosmic dawn significantly affected the big bang's afterglow known as cosmic microwave background (CMB).
- Scientists can trace the path of early cosmic ray photons through the ionized gas cloud created by these first stars, understanding their interactions.
- By measuring the probability that photons encounter freed electrons from neutral hydrogen atoms, scientists can better map the universe's transition from a dark, neutral fog into an ionized cosmos.
Cosmic microwaves have wavelengths just millimeters long and extremely faint signals. In contrast, polarized microwave light is even fainter, about a million times less potent. Earthly radio waves, radar, and satellites often overpower these microwaves, while changes in the atmosphere, weather, and temperature easily distort them. Even under ideal conditions, sifting through this type of microwave requires exquisitely sensitive equipment.
The fearless scientists from the U.S. National Science Foundation's Cosmology Large Angular Scale Surveyor (CLASS) project, unfazed by the challenges, used telescopes specially engineered to detect the unique patterns left by the first stars in the CMB remnants—something only space-based technology like NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck space telescopes had accomplished thus far.
The mind-blowing research, led by Johns Hopkins University and the University of Chicago, was published in The Astrophysical Journal. The team compared their CLASS telescope data with the data from both the Planck and WMAP space missions, finding common polarized microwave signals blowing the lid off a key piece of the cosmic microwave background puzzle.
First author Yunyang Li, a former Johns Hopkins PhD student, explained this discovery like this: "When light hits the hood of your car and you see a glare, that's polarization. To see clearly, you can put on polarized glasses to take away glare. 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, so to speak."
In the aftermath of the big bang, the universe was obscured by a fog of electrons that prevented light energy from escaping. As the universe expanded and cooled, protons captured the electrons to form neutral hydrogen atoms, and microwave light could finally travel freely. When the first stars ignited during the cosmic dawn, their immense energy forced electrons out of their hydrogen atoms. The research team measured the likelihood that a photon from the big bang encountered one of these freed electrons and veered off course.
The groundbreaking findings will help bring clarity to signals originating from the cosmic microwave background and create a clearer image of the early universe.
Charles Bennett, a researcher behind the WMAP mission, summed it up nicely: "For us, the universe is like a physics lab. Better measurements of the universe help to refine our understanding of dark matter and neutrinos, abundant but elusive particles that fill the universe. By analyzing additional CLASS data going forward, we hope to reach the highest possible precision that’s achievable."
This achievement builds on last year's research, in which the CLASS telescopes mapped 75% of the night sky, further solidifying the team's strategy and methods.
"No other ground-based experiment can do what CLASS is doing," says Nigel Sharp, program director in the NSF Division of Astronomical Sciences, who has supported the CLASS instrument and research team since 2010. "The CLASS team has shown that ground-based telescopes, with the right technology and location, can now provide valuable insights into cosmology research, especially when it comes to faint and distant signals from the universe's infancy."
- The Cosmology Large Angular Scale Surveyor (CLASS) project, led by Johns Hopkins University and the University of Chicago, has made significant strides in studying the cosmic dawn by using ground-based technology to detect the unique patterns left by the first stars in the remnants of the cosmic microwave background (CMB), a feat previously achieved only by space-based technology like NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck space telescopes.
- Ground-based telescopes, when equipped with the right technology, can provide valuable insights into the field of cosmology, especially for faint and distant signals from the universe's infancy. For instance, the CLASS project was able to measure the likelihood that a photon from the big bang encountered one of the freed electrons from neutral hydrogen atoms during the formation of the first stars, offering crucial details about the early universe.
- By refining measurements of the cosmic microwave background and continuing to analyze additional CLASS data, researchers hope to gain a more precise understanding of dark matter and neutrinos, elusive particles that are abundant in the universe. This groundbreaking work, following last year's mapping of 75% of the night sky using CLASS telescopes, showcases the potential for ground-based technology in contributing to the scientific understanding of space-and-astronomy and the history of the universe.
