Recent advancements in radio astronomy may soon illuminate the universe's dark ages, a period before the first stars and galaxies emerged. Traditional telescopes struggle to observe this elusive epoch, but innovative radio telescope arrays are poised to reveal critical insights.
Scientists have long relied on Einstein's general theory of relativity and quantum mechanics to understand cosmic phenomena, yet mysteries such as dark matter and dark energy remain largely unsolved. The cosmic microwave background (CMB), the afterglow of the Big Bang, has provided a foundation for understanding the universe's evolution over 13.8 billion years.
The cosmic dark ages, lasting from about 380,000 years post-Big Bang until the emergence of the first stars, are characterized by a lack of light. Theoretical models suggest that the first stars formed between 100 million and 400 million years after the Big Bang, ending this dark period.
New observatories, including the James Webb Space Telescope (JWST), have begun to peer into this early universe, revealing galaxies from when the universe was merely 330 million years old. However, JWST has yet to detect light from the very first stars.
A promising new approach involves detecting the 21-cm signal from hydrogen atoms, which can provide a three-dimensional map of the early universe. This signal arises from the spin-flip transition of hydrogen atoms and is influenced by the surrounding environment, including radiation from the first stars and black holes.
Experiments like the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the MeerKAT array have successfully detected the 21-cm signal from nearby neutral gas. The signal from the first stars is redshifted due to cosmic expansion, making it challenging to observe amidst stronger emissions from other sources.
Researchers are employing two main methods to detect this faint signal: global measurements from single antennas and spatial fluctuations using large interferometer arrays. The Square Kilometer Array (SKA), currently under construction, aims to provide a detailed tomographic scan of neutral hydrogen in the early universe.
Future proposals for radio arrays on the lunar far side may further enhance our ability to detect this signal, free from terrestrial interference. As scientists continue to refine their techniques, the potential to uncover the origins of the universe's first stars and galaxies grows closer.