What was the universe like 50 million years after the Big Bang? Astrophysicists haven’t known much about it, but a new study from Tel Aviv University (TAU) has predicted for the first time that groundbreaking results can be obtained from a lunar-based detection of radio waves.
The study, published in Nature Astronomy under the title “Prospects for precision cosmology with the 21 cm signal from the dark ages,” found that measured radio signals can be used for a novel test of the standard cosmological model, as well as to determine the composition of the universe and the weight of neutrino particles. In the future, they may also help scientists gain another clue to the mystery of dark matter.
This study was led by the research group of Prof. Rennan Barkana at TAU’s School of Physics and Astronomy, alongside postdoctoral fellow Dr. Rajesh Mondal. “A signal from the dark ages provides a potential new probe of fundamental cosmology,” they wrote. “While exotic physics could be discovered, here we quantify the expected benefits within the standard cosmology.”
Cosmology is the study of the history of the universe that led to the stars, galaxies, and other features of space that we observe today.
The researchers noted that the cosmic dark ages – the period just before the formation of the first stars – can be studied by detecting radio waves that were emitted from the hydrogen gas that filled the universe at that time. While the specific waves from the early universe are blocked by the Earth’s atmosphere. They can be studied only from space, especially the moon which offers a stable environment – free of any interference from the atmosphere and radio communications.
Significance of these findings
Obviously, landing a telescope on the moon is no simple matter, but we are witnessing an international space race in which many countries are trying to return to the moon with space probes and – eventually – astronauts. Space agencies in the US, Europe, China, and India are searching for worthy scientific goals for lunar development, and the new research highlights the prospects for detecting radio waves from the cosmic dark ages.
Barkana explained that “NASA’s new James Webb space telescope recently discovered distant galaxies whose light we receive from the cosmic dawn around 300 million years after the Big Bang. Our new research examined an even earlier and more mysterious era – the cosmic dark ages just 50 million years after the Big Bang. Conditions in the early universe were quite different from today.”
The new study, he added, “combines current knowledge of cosmic history with various options for radio observations to reveal what can be discovered. Specifically, we computed the intensity of radio waves as determined by the density and temperature of the hydrogen gas at various times, and then showed how the signals can be analyzed to extract from them the desired results.”
The researchers believe that the findings could be very significant for the scientific understanding of our cosmic history. A single lunar antenna, the standard model of cosmology, could be tested to see if it can explain the cosmic dark ages or if instead there was, for example, an unexpected disturbance in the expansion of the universe that would point towards a new discovery.
With a radio telescope consisting of an array of radio antennas, the composition of the universe – specifically, the amount of hydrogen and helium within it – could be determined accurately. Hydrogen is the original form of ordinary matter in the universe from which the stars, planets, and eventually humans were formed, the team wrote.
“A precise determination of the amount of helium is also of great importance, as it would probe the ancient period, around a minute after the Big Bang, in which helium formed when the entire universe was essentially a giant nuclear reactor. With an even larger array of lunar antennas, it will also be possible to measure the weight of cosmic neutrinos. These are tiny particles that are emitted in various nuclear reactions; their weight is a critical unknown parameter in developing physics beyond the established standard model of particle physics.
“When scientists open a new observational window, surprising discoveries usually result,” Barkana concluded. “With lunar observations, it may be possible to discover various properties of dark matter, the mysterious substance that we know constitutes most of the matter in the universe, yet we do not know much about its nature and properties. Clearly, the cosmic dark ages are destined to shed new light on the universe.”