An international team of scientists led by Israeli researchers has developed a method for detecting galaxies of stars that formed when the universe was still in its infancy – during the first 180 million years of its existence.
The universe is estimated to be about 14 billion years old, and the farther away a star is, the older it is. Current telescopes, however, can only identify galaxies about 700 million years old, and only when the galaxy is unusually large or a big stellar explosion has taken place.
Now, Prof. Rennan Barkana of Tel Aviv University’s School of Physics and Anatomy, is using radio telescopes to seek out radio waves emitted by hydrogen atoms, which were abundant in the early days of the universe.
Emitting waves measuring about 21 centimeters long, the atoms reflect the radiation of the stars, making their emission detectable by radio telescopes, explains Barkana. This development opens the way to learning more about the universe’s oldest galaxies.
Barkana explains that these waves show a specific pattern in the sky, a clear signature of the early galaxies, which were one-millionth the size of galaxies today. Differences in the motion of dark matter and gas from the early period of the universe, which affect the formation of stars, produce a specific fluctuation pattern that makes it easier to distinguish these early waves from bright local radio emissions.
The intensity of waves from this early era depends on the temperature of the gas, allowing researchers to begin to piece together a rough map of the galaxies in an area of the sky. If the gas is very hot, it means that there are many stars there; if cooler, there are fewer stars, explains Barkana.
These initial steps into the mysterious origins of the universe will allow radio astronomers to reconstruct for the first time what the early universe looked like, in terms of the distribution of stars and galaxies across the sky, Barkana believes.
“We know a lot about the pristine universe, and we know a lot about the universe today. There is an unknown era in between when there was hot gas and the first formation of stars. Now, we are going into this era and into the unknown,” says Barkana.