Astronomers find what could be the most distant galaxy yet

Astronomers have been jumping into each other’s pasts lately. Last week, a group using the Hubble Space Telescope announced that they had discovered what may be the most distant and earliest star ever seen, called Earendel, twinkling 12.9 billion years ago, just 900 million years after the Big Bang.

Now another international group of astronomers, testing the limits of Earth’s largest telescopes, say they’ve spotted what appears to be the earliest and most distant cluster of starlight ever seen: a reddish blob, usefully named HD1, containing prodigious amounts of Starlight emanated energy just 330 million years after the Big Bang. This time range has not yet been explored. Another blob, HD2, appears almost as distant.

Astronomers can only guess what these blobs are – galaxies or quasars, or maybe something else entirely – as they await their chance to observe them with the new James Webb Space Telescope. But whatever they are, astronomers say they may shed light on a crucial phase in the cosmos as it evolved from primordial fire into planets, life, and us.

“I’m as excited as a kid seeing the very first fireworks display in an amazing and highly anticipated show,” said Fabio Pacucci of the Harvard-Smithsonian Center for Astrophysics. “This could very well be one of the first glimmers of light to illuminate the cosmos in a show that ultimately created every star, planet and even flower we see around us today – more than 13 billion years later.”

dr Pacucci was part of a team led by the University of Tokyo’s Yuichi Harikane that spent 1,200 hours searching for very early galaxies using various ground-based telescopes. Their findings were published Thursday in the Astrophysical Journal and in the Monthly Notices of the Royal Astronomical Society. Her work was also featured in Sky & Telescope magazine earlier this year.

The farther an object is from us in the expanding universe, the faster it is moving away from us. Just as the tone of a retreating ambulance siren shifts to a lower tone, this movement causes an object’s light to shift to longer, redder wavelengths. Astronomers searched about 70,000 objects in search of the most distant galaxies, and HD1 was the reddest they could find.

“The red color of HD1 matched the expected properties of a galaxy 13.5 billion light-years away surprisingly well, giving me a little goosebumps when I found it,” said Dr. Harikane in a statement released by the Center of Astrophysics.

However, the gold standard for cosmic distances is the redshift, which is derived by obtaining a spectrum of the object and measuring how much the wavelengths emitted by characteristic elements have increased or redshifted. Using the Atacama Large Millimeter/submillimeter Array, or ALMA—a collection of radio telescopes in Chile—Dr. Harikane and his team gave a preliminary redshift for HD1 of 13, meaning that the wavelength of light emitted by an oxygen atom had stretched 14 times its wavelength at rest. The redshift of the other blob was not determined.

This dates the suspected galaxy to only 330 million years after the beginning of the calendar, right in the hunting ground of the Webb telescope, which can also be confirmed by the redshift measurement.

“If ALMA’s redshift can be confirmed, it would be a spectacular object indeed,” said Marcia Rieke of the University of Arizona, who is a principal investigator for the Webb telescope.

According to the story astronomers tell, the journey to the universe as we know it began about 100 million years after the Big Bang, when hydrogen and helium produced in the original explosion began to condense into the first stars known as population 3 stars (populations 1 and 2, which contain large amounts of heavier elements, are present in galaxies today). Composed of only hydrogen and helium, such stars have never been observed, and they would have been much larger and brighter than those in the universe today. They would have burned hot and died quickly in supernova explosions, which then started chemical evolution and polluted a pristine universe with elements like oxygen and iron, the stuff of us.

dr Pacucci said they first thought that HD1 and HD2 were so-called starburst galaxies being bloated by new stars. But after further research, they discovered that HD1 seemed to produce stars more than 10 times faster than such galaxies normally do.

Another possibility, said Dr. Pacucci, is that this galaxy produced these first-ever Population 3 ultraluminous stars. Another explanation is that all of this radiation comes from material squirting into a supermassive black hole that has 100 million solar masses. But astronomers have trouble explaining how a black hole could grow so large so early in cosmic time.

Was it born that way – in the chaos of the Big Bang – or was it just incredibly hungry?

“HD1 would represent a giant baby in the early universe delivery room,” said Avi Loeb, a co-author of Dr. Pacucci’s article.

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