Possible galaxy spotted by JWST could be the earliest we’ve ever seen

Astronomers may have detected a galaxy formed exceptionally early in the universe’s history, potentially 200 million years earlier than the known earliest galaxy. However, they advise caution regarding alternative interpretations.

Giovanni Gandolfi from the University of Padua in Italy and his team analyzed data from the James Webb Space Telescope (JWST) to identify distant astronomical objects formed in the nascent universe, which is approximately 13.8 billion years old.

The key to determining the age of these astronomic bodies lies in redshift — the phenomenon where the light from distant galaxies shifts towards the red spectrum due to the expansion of the universe. The further away a galaxy is, the longer its light takes to reach Earth, giving astronomers vital clues about its age.

The earliest confirmed galaxy to date, known as MoM-z14, possesses a redshift of 14.4, indicating that the light we now observe began its journey when the universe was only 280 million years old. In a striking discovery, Gandolfi and his colleagues report an object with a staggering redshift of 32, suggesting we view it as it was when the universe was just 90 million years old. This galaxy, dubbed “Capotauro,” takes its name from a mountain in Italy.

“Capotauro could potentially be the universe’s most distant galaxy,” stated Gandolfi, emphasizing its relevance during a critical period for the formation of the first stars and black holes.

The team’s findings stemmed from observing a faint signature in a comprehensive JWST sky survey that appeared to represent a faraway galaxy. By applying various filters, they were able to deduce the redshift value of 32.

Should this classification hold, Capotauro may represent an incredibly young galaxy undergoing formation stages, or it could be something even more extraordinary, such as a primordial black hole ensconced in a dense atmosphere, a theorized construct often called a black hole star.

However, this supposed galaxy exhibits an unusually bright signature, akin to later redshifted galaxies like MoM-z14. This implies a mass roughly one billion times greater than that of the sun, a figure that challenges existing models of galactic formation at such an early cosmic epoch.

Achieving such mass in the young universe would require nearly a perfect efficiency in converting gas into stars, nearly 100 percent, according to Nicha Leethochawalit at the National Astronomical Research Institute of Thailand. “It suggests no stars can explode during this rapid formation,” she remarked. However, prevailing models indicate efficiencies between 10 to 20 percent are typical. “I suspect something else is afoot,” she added.

If it turns out that Capotauro is not a galaxy, the researchers propose alternate explanations such as a brown dwarf — a star that never reached full size — or a rogue planet drifting within our galaxy’s vicinity, misleadingly resembling a distant galactic body. Such a finding would also be significant, hinting at potential substellar objects forming in the early stages of our galaxy’s lifetime.

“It might be one of the first substellar objects ever formed in our galaxy,” Gandolfi noted.

To clarify the nature of Capotauro, the research team would require additional observation time on the JWST to scrutinize the object’s light spectrum in greater depth. Leethochawalit expressed a preference for the notion that this is not a galaxy; nonetheless, she acknowledged the importance of follow-up studies.

“If confirmed as a galaxy with a redshift of 32, it would necessitate a fundamental reconsideration of some of our current understandings,” she concluded.