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This Galaxy Becomes The Farthest We've Ever Seen
She was shining 300 million years after the Big Bang
300 million years after the Big Bang, the galaxy HD1 was already shining. The celestial object has just been spotted by scientists, at a distance of 13.5 billion light-years from us.
This galaxy shone in the Universe just 300 million years after the Big Bang. Called HD1, this structure is described as the most distant astronomical object ever observed, in a press release from the Harvard-Smithsonian Center for Astrophysics on April 7, 2022.
Two teams of scientists have worked on HD1, their results having been accepted in The Astrophysical Journal (ApJ) and Monthly Notices of the Royal Astronomical Society Letters (MRNAS). It should be noted that one of the co-authors of the second text is Abraham Loeb: this scientist is a recognized cosmologist (for his work on the study of the structure of the Universe), but he is also at the origin of questionable theories about the interstellar object Oumuamua (despite not specializing in solar system physics). The theme addressed here is part of its original specialty.
What do we know about this galaxy so far away?
HD1 is located 13.5 billion light-years from us. The two teams of scientists wonder about its exact nature. The hypotheses mentioned are the following:
The galaxy is said to be forming new stars at a rapid rate. It may even contain population III stars. This hypothetical group would be that of the very first stars formed at the beginning of the Universe. But such stars have not yet been seen directly;
The galaxy could also contain a gigantic black hole 100 million times the mass of the Sun, which would make it a supermassive black hole.
Determining the characteristics of a galaxy so far away is complex. "It's like guessing the nationality of a ship from the flag it is flying while being far on land, and the ship is caught in the wind and a thick fog", compares Fabio Pacucci, an astrophysicist at the Smithsonian Astrophysical Observatory, the main author of the article published in MNRAS and co-author of the article in ApJ, quoted in the press release.
This Galaxy Becomes The Farthest We've Ever Seen
History of the Universe and formation of the first galaxies. // Source: Harikane et al., NASA, EST and P. Oesch/Yale
To study HD1, the researchers used more than 1,200 hours of observations conducted from several observatories: the Subaru Telescope (Hawaii), the VISTA Telescope (Chile), and the Spitzer Space Telescope (which has not been in operation since 2020). The giant ALMA radio telescope (Chile) was also mobilized to confirm the distance of HD1 and verify that it was more distant than the previous most distant galaxy known, GN-z11 (13.4 billion light-years).
It turns out that HD1 is bright in ultraviolet light, suggesting that the galaxy must be experiencing (or experienced a few billion years earlier) significant energetic processes. Scientists were also able to estimate that the galaxy forms more than 100 stars each year — 10 times more than expected for such a galaxy. It is for this reason that it is suspected that HD1 may not form normal stars, but population III stars… which are thought to be capable of emitting more ultraviolet light than the others.
But the black hole hypothesis cannot be ruled out, because it could quite swallow gas in large quantities and also explain the brilliance of HD1. Confirming the presence of such a black hole in this galaxy would be historic, as it would then be the first black hole known and observed so soon after the Big Bang.
The James Webb Telescope, which will soon be ready for its scientific observations in space, should help verify the distance between HD1 and our planet, and possibly confirm that this galaxy is the oldest ever detected.