Astronomers had goosebumps: the most distant galaxy ever detected, coming from the remote ages of the Universe 13.5 billion years ago, is described Friday in a study whose results have yet to be confirmed by further observations.
• Read also: Nasa’s final mega-rocket test for the Moon suspended
• Read also: Lunar dust at auction
It took more than 1200 hours of observing the sky, using four telescopes, to find “HD1”, a very luminous object whose “red color surprisingly corresponded to the characteristics of a galaxy located 13.5 billion years”, explains its discoverer Yuichi Harikane, in a press release published on the sidelines of the study by The Royal Astronomical Society.
An intuition that additional data, collected by the Alma observatory in Chile, have corroborated: HD1 is located 100 million years further than GN-z11, so far holder of the record for the most distant galaxy.
The galaxy HD1 would therefore have been born only 300 million years following the Big Bang, a period of the primitive Universe. And the light that emanates from it would have traveled for 13.5 billion years to reach the Earth.
To determine its age, scientists measured the redshift of its original light. As the Universe expands, the space between objects expands. And the more we go back in the past, the more these objects are distant and the more their light stretches, shifting towards increasingly red wavelengths.
“When I found this red, I had goose bumps,” says the astrophysicist from the University of Tokyo, one of the authors of the study published in Astrophysical Journal.
A black hole ?
But there is a catch: scientists have also measured an exceptionally strong intensity of ultraviolet radiation there, the sign of an activity that theoretical models of galaxy formation have not considered.
The authors of the study then put forward two hypotheses: the young galaxy would have been a particularly fertile ground for the formation of stars, producing around 100 of them per year – a rate ten times higher than expected.
These might be so-called “population III” stars that astronomers have never observed before. These first generations of stars were “more massive, brighter and hotter than + modern + stars”, according to Fabio Paccuci, of the Harvard Astrophysics Center (United States), main author of the study, quoted in the communicated.
Another track: the presence of a supermassive black hole in the heart of the galaxy. Who by engulfing gigantic quantities of gas would emit powerful radiation in the ultraviolet.
But for that, the black hole would have to be 100 million solar masses. “Reaching such a mass in such a short time is not very credible”, comments to AFP the astrophysicist Françoise Combes, of the Paris-PSL Observatory, who did not participate in the study.
To remove the unknowns, the HD1 galaxy was selected as a target for the James Webb Space Telescope and its unparalleled ability to see the very distant Universe.
