A team of astronomers recently announced to have detected the fingerprints of the very first stars of the Universe. An extraordinary insight into our history that will, hopefully, lift the veil on the early days of our Universe.
Long ago — about 400,000 years after the Big Bang — the Universe was dark: there were no stars or galaxies. On the other hand, the Universe was essentially filled with neutral hydrogen. For the next 50 to 100 million years, gravity caused the densest gas regions to collapse onto themselves, and the light was on. The first stars were born. But what did they look like? How did they affect the rest of the universe?
Today, after 12 years of efforts and experiments, researchers have announced that they have detected the fingerprints of the very first stars in the Universe. Led by astronomer Judd Bowman, of the ASU School of Earth and Space Exploration, the team has indeed detected the oldest stars of the universe. These would have appeared 180 million years after the beginning of the Universe.
“It was a huge technical challenge because the noise sources can be a thousand times brighter than the signal – it’s like being in the middle of a hurricane and trying to hear the flutter of a hummingbird’s wing,” says Peter Kurczynski, program director at the National Science Foundation also behind this study. “These researchers with their small radio antenna in the desert have seen beyond the most powerful space telescopes, opening a new window to the primitive universe.”
The researchers relied on a radio spectrometer at the Murchison Radio Astronomy Observatory (MRO) in Western Australia. They began by measuring the average radio spectrum of all the astronomical signals perceived. This maneuver has been applied to a large part of the southern hemisphere sky, to try to detect power changes – even tiny ones – depending on the wavelength. In this study, the signals that were detected by the radio spectrometer came from the hydrogen that filled the young Universe. These signals are a considerable source of information, providing a new perspective on the formation and evolution of the first stars – and later, black holes and galaxies.
“It is unlikely that we will be able to see even earlier in the history of stars in our lifetime,” says Bowman. In addition, the results obtained confirm the different theories concerning the formation of the first stars and their most important characteristics. “What happens during this period is that part of the radiation from the very first stars begins to allow the hydrogen to be seen, causing the absorption of background radiation. This was first real signal emitted by the stars that began to form,” one can read in Nature.
The researchers also claimed that the gas in the Universe was surely significantly colder than expected. In fact, its temperature would be less than half the expected temperature. This discovery suggests that in their assumptions, astrophysicists have neglected an important element. On the other hand, this could be the first proof of out-of-frame physics: an interaction between baryons (normal matter) and dark matter, which today constitutes 85% of matter in the Universe.
The next steps in this line of research will be to calibrate new instruments to learn more about the properties of the first stars. “Now that we know this signal exists,” says the researcher, “we must quickly bring new radio telescopes online that can extract the signal much more deeply.”