Wednesday, February 21

We’ve just identified a candidate for the farthest galaxy ever seen: here’s what we know about HD1


An international team of astronomers, including researchers from the Harvard & Smithsonian Center for Astrophysics, has discovered what could be the farthest and oldest galaxy ever observed. The intriguing astronomical object, called HD1, is located at a distance of 33.4 billion light-years from Earth, if we take into account the expansion of the universe, and was already in existence just 330 million years after the Big Bang. We now see it as it was 13.5 billion years ago.

The discovery of this object raises questions in the researchers. In an article published in the Monthly Notices of the Royal Astronomical Society Letters, the scientists propose two possible theories about what exactly this discovery of the early universe is. “Answering questions about the nature of such a distant source can be challenging,” says Fabio Pacucci, lead author of the study.

Is it the oldest and most distant galaxy?

HD1 is very bright at ultraviolet wavelengths, which could mean that whatever produced its light was extremely hot. Consequently, according to astronomers, two ideas emerge: either there was a star formation “burst” much larger than we would normally expect in a galaxy of relatively small size or was home to a active supermassive black hole.

Timeline Hd1

In the first case, HD1 should have produced the equivalent of more than a hundred stars with the mass of our sun every year, a phenomenon that is difficult for experts to explain. One possibility is that this galaxy might not have formed normal stars, but rather Population III stars that were much more massive and much hotter than nearby normal stars.

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“The first population of stars to form in the universe was more massive, more luminous and hotter than modern stars. If we assume that the stars produced in HD1 are these first, or Population III stars, then their properties could be further explained. In fact, Population III stars are capable of producing more ultraviolet light than normal stars, which could brighten HD1’s extreme ultraviolet luminosity.”

The other theory is that HD1 could be home to a huge supermassive black hole. Now, the existence of a black hole of 100 million solar masses in the early universe would be a challenge for science, because couldn’t explain how it was formed. HD1 is only 330 million years from the Big Bang, which experts consider too short a time for such a large black hole to have formed.

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Avi Loeb, co-author of the study, also known for promoting some controversial ideas such as that Oumuamua was an alien spacecraft and that our universe could have been created in a laboratory, explains that at form a few hundred million years after the Big Bang, HD1’s black hole must have grown from a massive seed at an unprecedented rate. “Once again, nature seems to be more imaginative than we are,” she muses.

The team explains that HD1 was detected thanks to the observation work carried out with the Subaru (Hawaii), VISTA Telescope (Chile), UKIRT (United Kingdom) and Spitzer (United States) telescopes. He then made follow-up observations using the Atacama Large Millimeter/submillimeter Array (Chile) to confirm the distance, which is about 100 million light-years further than GN-z11, the current farthest galaxy.

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Later this year the team hopes to continue collecting data from HD1 with the James Webb Space Telescope. With this powerful instrument in orbit, which is considered a “time machine”, your distance from Earth will be re-verified. In case the calculations confirm it, it will officially be the most distant and oldest galaxy ever recorded. For now, that’s just one of the possible theories. With time we will know if it is correct.

More information | Harvard & Smithsonian Center for Astrophysics

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