Suitcase-sized spacecraft may reveal what happened before first stars formed

CosmoCube could use the Moon’s far side as a natural shield from radio interference generated on Earth.(Image: Surrey Space Technology Ltd)A proposed suitcase-sized satellite could give astronomers a new way to study the universe’s earliest stages by listening for faint radio signals from more than 13.5 billion years ago. The mission, called CosmoCube, would operate near the Moon and use the lunar far side as a natural shield against radio interference from Earth. Researchers say the concept could help scientists study the poorly understood period between the Big Bang and the formation of the first stars.Why the early universe is difficult to observe After the Big Bang, the universe entered a period known as the cosmic dark age. It lasted roughly 150 million years before the first stars began to form. Although there were no stars yet, the universe was filled with hydrogen. These atoms produced a faint radio signal known as the 21-centimetre line, which carries information about conditions in the early universe. Detecting this signal from Earth, however, is extremely difficult. Earth’s ionosphere blocks the relevant low-frequency radio waves, while human-made signals from FM radio, telecommunications systems, and satellites can further overwhelm the extremely faint cosmic signal. The result is a major observational gap in our understanding of the universe’s early history. CosmoCube would use Moon as a shield The international team behind CosmoCube proposes placing the small spacecraft in orbit around the Moon, allowing it to collect measurements as it passes behind the Moon’s far side.Story continues below this ad The Moon would block radio noise originating from Earth, creating a much quieter environment for the spacecraft’s instruments. According to the researchers, CosmoCube would spend around 40 minutes on the far side during every two-hour orbit. Over a proposed two-year mission, the satellite could collect roughly 1,000 hours of data at extremely low radio frequencies. The measurements could offer scientists a clearer picture of the cosmic dark age and the transition towards the formation of the first stars and galaxies. What could the signal reveal? One of the major questions CosmoCube could help address concerns dark matter and its role in the early universe.Story continues below this ad Scientists believe dark matter’s gravitational influence helped pull hydrogen and other matter together, eventually contributing to the formation of the first stars and galaxies. Studying the 21-centimetre signal could therefore provide clues about how these structures emerged from the early universe. Eloy de Lera Acedo, an astronomer at the University of Cambridge and co-author of the study, said the far side of the Moon offers a unique combination of protection from Earth’s radio interference and a broad view of space. A small spacecraft with a difficult job Despite its relatively small size, CosmoCube would require sophisticated systems to distinguish the faint cosmic signal from noise produced by the spacecraft itself and other sources. The satellite would use a lightweight radio antenna to detect the early-universe signal. It would also repeatedly determine its own position using onboard information and observations of its surroundings.Story continues below this ad These checks would help researchers identify interference originating from the spacecraft and prevent it from being mistaken for a genuine cosmic signal. After the mission, mathematical models would be used to remove additional foreground interference, including radio emissions from the Milky Way and other sources. Will Grainger, an astronomer and study co-author, said the mission would require “clever design techniques” to carry out ambitious science from a small spacecraft operating in a challenging environment. Mission could be ready within five years The researchers are working with partners to develop and test CosmoCube models,