Astronomers had goosebumps: the most distant galaxy ever to come from the universe’s distant epoch 13.5 billion years ago is described in a study Friday, the results of which have yet to be confirmed by further observations.
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Its discoverer Yuichi Hurricane explains, using four telescopes, to find “HD1”, a very bright object whose “reddish color surprisingly matches the characteristics of the Milky Way located 13.5 billion years ago”. It took over 1200 hours to watch. A press release published by The Royal Astronomical Society on the sidelines of the study.
An intuition that additional data collected by the ALMA Observatory in Chile has confirmed: HD 1 is located 100 million years ahead of GN-z 11, the holder of the record for the most distant galaxy ever discovered.
Therefore the galaxy HD1 would have been born only 300 million years after the Big Bang, the period of the primordial universe. And the light emanating from it must have traveled 13.5 billion years to reach Earth.
To determine its age, scientists measured the redshift of its parent light. As the universe expands, the space between objects expands. And the further we go back in the past, the farther away these objects are and the more their light spreads, the faster it is moving towards the red wavelengths.
“When I found it red, my hair went up,” says an astrophysicist at the University of Tokyo, one of the authors of the study published in the Astrophysical Journal.
a black hole?
But there’s a catch: Scientists have also measured an extraordinarily strong intensity of ultraviolet radiation there, indicating an activity that theoretical models of galaxy formation have not considered.
The study’s authors then put forward two hypotheses: Young galaxies may have been a particularly fertile ground for star formation, producing about 100 of them per year – a rate ten times higher than expected.
These may be so-called “population III” stars that astronomers have never seen before. These first generations of stars were “more massive, brighter and hotter than modern + stars”, according to Fabio Pacucci of Harvard Astrophysics Center (United States), lead author of the study, cited in Communications.
Another track: the presence of a supermassive black hole at the center of the galaxy. Who would swallow the gas in huge quantities and emit powerful radiation in the ultraviolet.
But for that, the black hole would have to be 100 million solar masses. “It is not very reliable to reach such a mass in such a short time”, commented AFP astrophysicist François Combs of the Paris-PSL Observatory, who did not take part in the study.
To address the unknown, the HD1 galaxy was chosen as a target for the James Webb Space Telescope and its unique ability to observe the very distant universe.
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