An international team of astrophysicists and astronomers has developed a new method for detecting galaxies of stars that formed during the first 180 million years of the Universe’s existence.
Hubble image of UDFj-39546284, one of the oldest galaxies ever observed. Astronomers believe that its light has taken 13.2 billion years to reach us. The galaxy has a redshift of 10.3. The new method allows to detect objects with redshifts as high as 20 (NASA / ESA / G. Illingworth / R. Bouwens / the HUDF09 team)
“The method is able to observe stars that were previously believed too old to find,” said Prof Rennan Barkana of the Tel Aviv University’s School of Physics and Astronomy.
The new method, described in a paper in the journal Nature (arXiv.org version), uses 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 cm long, the atoms reflect the radiation of the stars, making their emission detectable by radio telescopes,” Prof Barkana said. “This development opens the way to learning more about the Universe’s oldest galaxies.”
“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 much 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,” Prof Barkana explained.
“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, specifically in terms of the distribution of stars and galaxies across the sky.”
“This field of astronomical research, now being called ‘21-centimeter cosmology,’ is just getting underway. Five different international collaborations are building radio telescopes to detect these types of emissions, currently focusing on the era around 500 million years after the Big Bang. Equipment can also be specifically designed for detecting signals from the earlier eras.”
“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.”
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Bibliographic information: Eli Visbal et al. 2012. The signature of the first stars in atomic hydrogen at redshift 20. Nature 487, 70–73; doi: 10.1038/nature11177
