An international team of astronomers has discovered the most distant astronomical object observed so far, a galaxy that has been baptized as HD1 and that is about 13,500 million light years away.
Details of the find are described in Magazine Astrophysical Journal, and in an accompanying article, published in Monthly Notices of the Royal Astronomical Society Letters, Scientists put forward the first hypotheses about the type of galaxy it may be.
HD1 could contain primitive stars never observed
The team of astronomers, including researchers from the Harvard Center for Astrophysics and the Smithsonian, propose two ideas: that HD1 is forming stars at an astonishing rate and that it even contains Population III stars – the first in the universe – that have never been seen before. have been observed, or contain a supermassive black hole with a mass a hundred million times that of our Sun.
“Answering questions about the nature of such a distant source can be challenging,” says Fabio Pacucci, lead author of the study and an astronomer at the Center for Astrophysics.
“It’s like guessing the nationality of a ship from the flag it flies, being far away on land, with the ship in a gale and heavy fog. One can see perhaps some colors and shapes of the flag, but not in its entirety. It is a long game of analysis and exclusion of implausible scenarios,” he warns.
For now it is known that HD1 is extremely bright in ultraviolet light, which means that “some energetic processes are happening there or, better yet, they happened a few billion years ago,” says Pacucci.
HD1, forming stars at an amazing rate
At first, the researchers assumed that HD1 was a standard galaxy that is creating stars at a high rate, but after doing the math, they found that HD1 is producing them at an “incredible rate” of more than 100 stars per year, a figure “at least 10 times higher than what we expect for these galaxies”, comments the astronomer.
That’s when the team began to suspect that HD1 might not be forming run-of-the-mill stars.
“The first population of stars to form in the universe was more massive, more luminous and hotter than modern stars,” says Pacucci.
“If we assume that the stars produced in HD1 are these first, or Population III stars, then their properties could be more easily explained. In fact, Population III stars are capable of producing more ultraviolet light than normal stars, which that could brighten the extreme ultraviolet luminosity of HD1,” he reasons.
Supermassive black hole?
However, another possible explanation for HD1’s extreme luminosity could well be the existence of a supermassive black hole, since by engulfing huge amounts of gas, the region surrounding the black hole could emit high-energy photons.
If so, it would be by far the earliest supermassive black hole known to mankind, much closer to the Big Bang than the one that currently holds that record.
As Avi Loeb, an astronomer at the Center for Astrophysics and co-author of the study, explains, “HD1 would represent a giant baby in the delivery room of the early universe.”
But, in addition, “forming a few hundred million years after the Big Bang, a black hole in HD1 must have grown from a massive seed at an unprecedented rate. Once again, nature seems to be more imaginative than we are.” Loeb concludes.
Corroborating observations with data from the James Webb Telescope
HD1 was discovered after more than 1,200 hours of observing with the Subaru, VISTA, UK Infrared Telescope and Spitzer Space Telescope.
Now, using the James Webb Space Telescope, the team will once again observe HD1 to verify its distance from Earth, and if current calculations are correct, HD1 will be the farthest – and oldest – galaxy ever found.
These observations will allow us to find out more about HD1 and confirm which of their theories is correct.
FEW (EFEAstrophysical Journal, Center for Astrophysics)