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Paris (AFP) – Astronomers have goosebumps: the farthest galaxy ever detected, born in the early universe 13.5 billion years ago, was described in a study whose results must be confirmed with more leisurely observations.
It took more than 1,200 hours of observation of the sky and the help of four telescopes to find “HD1”: a very bright object whose “red color surprisingly corresponds to the characteristics of a galaxy located 13.5 billion years ago”, explains its discoverer. Yuichi Harikane, in a statement published alongside the study on Friday by The Royal Astronomical Society.
The intuition was corroborated by complementary data collected by the Alma observatory in Chile: HD1 is located 100 million years further away than GN-z11, the farthest galaxy discovered so far.
The HD1 galaxy was born just 300 million years after the Big Bang, in a very early period of the universe. And the light it emanates has traveled for 13.5 billion years to reach Earth.
To determine its age, scientists measured the red shift of its source light. As the universe is expanding, the space between objects widens. And the further back into the past we go, the farther away these objects are and the more their light is stretched, shifting to increasingly redder wavelengths.
“When I found this red, I got goosebumps,” explains the astrophysicist at the University of Tokyo, one of the authors of the study that appeared in the Astrophysical Journal.
Fertile galaxy for stars?
But there’s a problem: Scientists have also measured an exceptionally strong intensity of ultraviolet radiation, a sign of activity that theoretical models of galaxy formation hadn’t predicted.
The authors of the study point to two hypotheses: the young galaxy would be a particularly fertile ground for star formation, producing up to a hundred per year, a rate ten times higher than expected.
It could be the so-called Population III stars that astronomers have yet to observe. They are primitive stars that were “more massive, more luminous and hotter than modern stars,” according to Fabio Pacucci, from the Center for Astrophysics at Harvard (United States), lead author of the study cited in the statement.
Another option may be the presence of a supermassive black hole in the heart of the galaxy that absorbs huge amounts of gas and emits powerful ultraviolet radiation.
But for this, the black hole would have to have 100 million times the mass of the Sun. “Reaching such a mass in such a short time is hardly credible,” astrophysicist Françoise Combes, from the Paris-PSL Observatory, told AFP, who did not participated in the study.
To resolve these unknowns, the HD1 galaxy has been selected as a priority target for the James Webb Space Telescope and its unparalleled ability to view the most distant Universe.
© 2022 AFP