The red part, HD1, is the farthest galaxy astronomers have ever seen. Image credit: Team Yuichi Harikane
Recently, American and Japanese astronomers have observed a galaxy called HD1, which may be the farthest galaxy to date. Its astonishing brightness also makes it difficult for astronomers to explain, possibly due to a giant black hole at the center of a galaxy, or a massive primordial star. The results were published in the Monthly Journal of the Royal Astronomical Society and the Journal of Astrophysics, respectively.
In one of these studies, the Fabio Pacucci team at the Harvard-Smithsonian Center for Astrophysics sifted through observations from several of the most powerful telescopes and eventually discovered HD1. Subsequently, they made further observations of HD1 using the Atacama Large Millimeter/Submillimeter Array (ALMA).
The observations suggest that HD1 is about 33.4 billion light-years from Earth, 1 billion light-years away from the most distant galaxy previously discovered, GN-z11. Although the age of the universe is only about 13.8 billion years, such a distance is possible due to the accelerated expansion of the universe.
The researchers found that the galaxy is very bright at ultraviolet wavelengths, meaning its luminous objects can be very hot. The study suggests there are two possible ways to make it so bright: either it’s experiencing a star-forming explosion that’s far larger than we would expect from a relatively small galaxy, or it’s home to an active supermassive black hole.
If the answer is the former, HD1 would have to produce about 110 stars per year that are about 110 times the mass of the Sun. “It’s a crazy number. This galaxy may not have formed normal stars, but these primordial stars are much larger and hotter than nearby normal stars. We’ve never seen such a primordial star before. Pacucci said.
Another explanation is that HD1 may have an unexpectedly large supermassive black hole. “Observing a black hole with 100 million times the mass of the Sun early in the history of the universe would be very groundbreaking because we really aren’t sure how it formed.” Pacucci explained that black holes take time to grow, and THAT HD1 is so far away that what WE see now is what HD1 looks like 330 million years after the Big Bang, so it’s unclear how a black hole could have become so large in such a short period of time.
The researchers say more observations are needed to determine the extreme distance of HD1 and figure out why it is so bright. For now, researchers have obtained observation time from the James Webb Space Telescope to observe HD1 and two other objects called HD2 and HD3, which seem as far away as we are. (Source: China Science Daily Xin Yu)
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