The early galaxies were relatively small and dim, lighter than those of the present day, according to the study
A first-of-its-kind study from Israel’s Tel Aviv University managed to statistically characterize the first galaxies in the universe, leading to groundbreaking results.
The galaxies, which formed only 200 million years after the Big Bang, were relatively young and dim. According to the study published in the journal natural astronomyThe first galaxies were lighter than present-day ones, likely processing only 5 percent or less of their gas into stars.
“This is a very new field and a first-of-its-kind study,” Professor Renan Barcana, of the Sackler School of Physics and Astronomy, described the undertaking and explained that the team was trying to understand the era of the first stars, known as the “cosmic dawn.”
“The James Webb Space Telescope, for example, can’t really see these stars,” Barkana said. “It may only detect a few particularly bright galaxies from a somewhat later period. Our goal is to examine the entire population of the first stars.”
Barkana was one of the first theorists about 20 years ago to develop the concept of using hydrogen as a detector in the search for the first stars and as a way to understand when they were born and in what kind of galaxies.
Hydrogen atoms naturally emit light with a wavelength of 21 cm, which is in the radio wave spectrum. These atoms fill the universe, but in modern times they are mostly ionized as a result of star radiation.
In 2018, the EDGES team tried to use this theory and announced that it had found a 21 cm signal of ancient hydrogen. However, Barkana pointed out a problem with their findings.
“We couldn’t be sure that the measured signal actually came from hydrogen in the early universe. It might have been a fake signal caused by the electrical conduction of the Earth under the antenna.”
He noted that there was a 95 percent chance that EDGES had not in fact detected a real signal, adding, “Now we can say for the first time that certain types of galaxies could not have existed that early.”
“Each year the experiments become more reliable and precise, and so we expect to find stronger upper bounds, which will give us better constraints on the cosmic dawn. We hope that in the near future we will not only have a bound, but also an accurate and reliable measurement of the signal itself.”
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