Hidden behind dust: the University of Geneva discovers two ancient galaxies
An international team led by the University of Geneva has discovered two previously unknown galaxies. These formed more than 13 billion years ago.
Unexpected signals from apparently empty regions of space: Astronomers led by the University of Geneva, the University of Waseda (Japan) and the National Astronomical Observatory of Japan (NAOJ) have discovered two previously unknown galaxies that are heavily obscured by cosmic dust. This discovery suggests that many more such galaxies may be hidden in the early universe than previously thought. The University of Geneva announced on Wednesday. The discovery of the galaxies that formed more than 13 billion years ago was published in the journal Nature.
The exploration of this early universe is considered to be one of the final frontiers of astronomy. Since the speed of light is limited, examining the most distant galaxies allows a glimpse into the past, when the universe was very young and galaxies were just beginning to form stars.
The discovery was made thanks to the Atacama Large Millimeter Array (Alma) radio telescope observatory in Chile. As part of the Rebels research program, astronomers with Alma observe the emission of 40 target galaxies in the cosmic dawn in the sub-millimeter wavelength range, as it is said. When analyzing the observation data from two of the rebel galaxies, the astronomers encountered strong signals that were well removed from the original targets. It was found to originate from two previously unknown galaxies that are close to the two original rebel targets.
“These galaxies are not visible in the UV range or in optical light because they are quickly completely covered by cosmic dust,” says Pascal Oesch, professor at the Institute for Astronomy at the University of Geneva, in the cited communication.
Suspected more galaxies behind dust
This dust is also the reason why they remained hidden for so long. Because they are not strange compared to typical galaxies from the same period. “These new galaxies did not go unnoticed because they are extremely rare, but only because they are completely covered by dust,” says Yoshinobu Fudamoto from Waseda University. “Our discovery suggests that there could be a large, unrecognized star-forming galaxy that is hidden behind dense dust and undetected by the Hubble telescope.”
The researchers therefore assume that the record of early galaxy formation is incomplete and further investigations are necessary. “Our discovery shows that the very early universe probably confirms many more galaxies than we currently assume,” says Oesch. The researchers place their hopes in the James Webb Space Telescope (JWST) and Alma. “The combination of JWST and Alma data will soon tell us exactly how many galaxies we have missed so far. So we can solve when the first galaxies in the early universe were formed. (abi)