Astronomers predict a new observational technique that relies on the detection of faint radio signals will allow them to see the first stars formed in dense clouds of hydrogen shortly after the birth of the universe.
The technique, introduced in a new paper, looks for a signature type of electromagnetic radiation known as the 21-centimeter line, emitted by hydrogen atoms that filled the young universe in the first hundreds of thousands of years after the Big Bang. Had given.
The signal is very weak, about a million times weaker than the radio signal emitted by the object in our galaxy, the Milky Way. It would require complex data analysis to separate the signal from all other interference detected by radio antennas.
“Our method jointly analyzes data from multiple antennas and detects a broader frequency band than equivalent current instruments,” said Eloy de Lera, an astronomer at the University of Cambridge in the UK and lead author of the new paper, in a statement. Acedo said. Space, 23 July 2022.
By measuring the difference between the radiation from the hydrogen cloud and the signal behind it, astronomers hope to ‘see’ the stars as if they were “shadows in the fog”.
“By the time the first stars formed, the universe was largely empty and composed mostly of hydrogen and helium,” de Lera Acedo said in a statement. “Because of gravity, the elements eventually came together and the conditions were just right for nuclear fusion, which created the first stars. But they are surrounded by a cloud called neutral hydrogen, which absorbs light very well, That’s why it’s difficult to detect or observe. The light behind the clouds. Directly.”
The James Webb Space Telescope, which recently released its first science images, is looking for the universe’s first light, but using a different technique. Webb detects infrared radiation, which is basically heat. Because heat can penetrate dust clouds, Webb allows astronomers to peek into even the most impenetrable regions of the universe.
The new radio astronomy method was developed as part of the Radio Experiment for Analysis of Cosmic Hydrogen (REACH) project and builds on previous observations indicating the 21-centimeter line of detection. The previous measurements could not be replicated, leading the scientists to believe that the signal may have been an error.
“If we can confirm that the signal detected in the previous experiment did indeed come from the first star, the effect would be much larger,” said de Lera Acedo.
The researchers used simulations that mimic real observations using multiple radio antennas, increasing the reliability of the data compared to previous measurements that relied on a single antenna. The new measurements will take place later this year in Karoo, South Africa.
“We are excited to see how well the system will work, and we are very confident that we will identify the elusive,” said Dirk de Villiers, a radio astronomer at Stellenbosch University in South Africa and a co-author of the new study. in a statement.
Scientists had previously detected signals from the Big Bang as a cosmic microwave background, but the appearance of the universe’s first stars is still missing after the early Dark Ages of hundreds of thousands of years. The paper was published in the journal Nature Astronomy on Thursday, July 21, 2022.