This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A tiny UK-developed satellite, roughly the size of a small carry-on suitcase, could help answer one of the biggest questions in cosmology: What happened during the roughly 150 million years of the cosmic dark ages, before the universe's first stars appeared? An international team of scientists led by the University of Cambridge will use the far side of the moon as a "shield" so the satellite—called CosmoCube—can block out all the noise from Earth and listen for a faint whisper from the very early universe.
This whisper, known as the 21-centimeter line, is a signal emitted by hydrogen atoms in the period between the afterglow of the Big Bang and cosmic dawn, when nuclear fusion lit up the first stars. No one has directly observed this era before. Detecting this signal from more than 13.5 billion years ago is extremely difficult with Earth-based telescopes because Earth's ionosphere blocks the right frequencies, and interference from FM radio, satellites and telecommunications drowns it out.
However, the moon provides a natural shield. As CosmoCube orbits the far side of the moon, it will be shielded from all the noise from Earth for roughly 40 minutes of each 2-hour orbit. Over an expected 2-year mission, it will build up 1,000 hours of data on one of the last unexplored periods of the universe, helping us understand how the universe transitioned from dark and nearly empty to the complexity we see today.
The mission has received funding from the UK Space Agency, and the researchers hope CosmoCube can be launched within the next five years. Details are published in the journal Nature Astronomy. In addition to exploring the universe in the period before the first stars, CosmoCube will also explore the role of dark matter—the mysterious force that holds galaxies together.
"This emission from hydrogen after the Big Bang, but before the first stars, will hopefully allow us to understand the role of dark matter in the early universe, how it worked to pull together hydrogen into the first stars and galaxies," said lead author Professor Eloy de Lera Acedo of Cambridge's Cavendish Laboratory. To study this period, CosmoCube will operate at extremely low frequencies—between 10 and 50 MHz—far outside the range of ground-based telescopes, which is why the moon will be used as CosmoCube's "fortress of solitude." "There's no other place where you can get the sort of shielding you need to detect such a faint signal, while at the same time looking at all of space," said de Lera Acedo, who is also affiliated with the Kavli Institute for Cosmology. "The far side of the moon is really the only option: It solves multiple problems at once, opening a clear window to the very early universe." Once in orbit around the moon, CosmoCube will unfold a long, lightweight radio antenna sensitive enough to detect the 21-centimeter signal from hydrogen atoms in the early universe when the satellite is on the moon's far side.
While in lunar orbit, CosmoCube will constantly check and correct its own electronics using a "Dicke switched" calibrator, which will flip between the sky and several built-in reference sources. This will help cancel out tiny drifts and noise inside the satellite that could otherwise masquerade as cosmic signals. Once CosmoCube's data is back on Earth, the team will use advanced Bayesian statistical methods to remove foreground noise—mainly radio emissions from our own galaxy.
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