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Astronomers discover farthest-away known galaxy, dubbed HD1

At 13.5 billion light-years away, HD1 is among the farthest flung celestial bodies from Earth — which explains why it was so difficult to detect.

(CN) — An international team of astronomers, including researchers at Harvard University and the Smithsonian Institution, glimpsed a snapshot of the universe’s distant past in a galaxy 13.5 billion light-years away — the farthest anyone has observed into space so far.

Named HD1, the galaxy was observed after more than 1,200 hours with a series of telescopes, including the Subaru Telescope, VISTA Telescope, UK Infrared Telescope and the Spitzer Space Telescope. The sheer scale of the universe made the galaxy challenging to detect.

“It was very hard work to find HD1 out of more than 700,000 objects,” said Yuichi Harikane, the University of Tokyo astronomer who discovered HD1. “HD1’s red color matched the expected characteristics of a galaxy 13.5 billion light-years away surprisingly well, giving me a little bit of goosebumps when I found it.”

Using a maritime example, lead study author and Center for Astrophysics astronomer Fabio Pacucci likened locating the galaxy to identifying a ship at sea.

“It’s like guessing the nationality of a ship from the flag it flies, while being far away ashore, with the vessel in the middle of a gale and dense fog,” Pacucci said. “One can maybe see some colors and shapes of the flag, but not in their entirety.”

Due to the time it takes for light to reach Earth through the vastness of space, researchers believe that HD1 will be the oldest galaxy ever recorded once the James Webb Space Telescope verifies it.

Pacucci explained in the release that HD1’s bright ultraviolet light could indicate that “some energetic processes are occurring there, or better yet, did occur some billions of years ago,” he said.

Because this galaxy formed so comparatively early in the history of the universe, researchers formed dueling theories as to HD1’s celestial makeup. The first suggests that the newly observed galaxy contains earlier, larger iterations of stars, and the second presents the possibility of a giant black hole — roughly 100 million times the mass of our sun — at the galaxy’s center.

The first theory suggested that HD1 is producing one of the earliest types of star after dismissing the possibility of the galaxy producing stars at an unusually high rate.

“HD1 would be forming more than 100 stars every single year. This is at least 10 times higher than what we expect from these galaxies,” Pacucci said.

Upon further observation, Pacucci posited that “If we assume the stars produced in HD1 are these first, or Population III, stars, then its properties could be explained more easily. In fact, Population III stars are capable of producing more UV light than normal stars,” which Pacucci said was reflected in the galaxy’s high output.

However, stars are not the only celestial bodies to produce ultraviolet light at such an intensity. According to the study, supermassive black holes engulf high amounts of surrounding gases, which produce photons that send ultraviolet light outward, which could explain HD1’s luminosity.

If HD1 does contain a supermassive black hole, it would predate the oldest previously known supermassive black hole on record — and closer in time to the Big Bang itself.

“HD1 would represent a giant baby in the delivery room of the early universe,” Center for Astrophysics astronomer Avi Loeb said in the release.

Regardless of the source of HD1’s energy output, researchers confirmed the surprising nature of the galaxy.

“Forming a few hundred million years after the Big Bang, a black hole in HD1 must have grown out of a massive seed at an unprecedented rate,” Loeb said. “Once again, nature appears to be more imaginative than we are.”

The researchers’ study was published Thursday in Monthly Notices of the Royal Astronomical Society Letters, a peer-reviewed journal.

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