Earendel: The Distant Star That Might Be a Star Cluster

In a groundbreaking twist in astronomical research, the most distant star ever discovered, known as Earendel, may not be a single star after all. New findings suggest that this celestial object, which was initially identified by the Hubble Space Telescope in 2022, could actually be a star cluster—a gravitationally bound group of stars formed from the same gas and dust cloud. This revelation shines a new light on our understanding of the universe’s early years.

Earendel, which derives its name from the Old English word for “morning star,” was believed to have formed just 900 million years after the Big Bang, making it a remarkable relic from an era when the universe was only 7% of its current age. The study that brought this possibility to light was published on July 31 in The Astrophysical Journal, where astronomers utilized the advanced capabilities of the James Webb Space Telescope (JWST) to reassess the characteristics of Earendel.

The research team, led by Massimo Pascale, a doctoral student at the University of California, Berkeley, employed JWST’s instruments to investigate whether Earendel could be a compact star cluster rather than a solitary star. Their analysis revealed that the spectral features of Earendel closely resemble those of globular clusters observed in the local universe, which are known for their dense collections of stars.

“What’s reassuring about this work is that if Earendel really is a star cluster, it isn’t unexpected!” Pascale remarked. He emphasized that the findings align with expectations of how globular clusters might have appeared in the universe’s first billion years.

Earendel is located in the Sunrise Arc galaxy, approximately 12.9 billion light-years away from Earth. Its discovery was made possible through gravitational lensing, a phenomenon predicted by Einstein’s theory of general relativity. This effect occurs when massive objects, such as galaxy clusters, bend the light from more distant objects, allowing astronomers to observe them despite their faintness. In Earendel’s case, it appears at least 4,000 times larger due to this lensing effect, making it visible even from such immense distances.

Astronomers first identified Earendel using data from JWST’s Near Infrared Imager (NIRCam), initially concluding that it was a massive star, potentially more than twice as hot as the sun and a million times more luminous. However, Pascale’s team later explored the star cluster hypothesis, driven by the intriguing possibility that Earendel could be much larger than previously thought.

The researchers utilized spectroscopic data from JWST’s NIRSpec instruments to delve deeper into Earendel’s properties, including its age and metal content. They found that the spectral continuum—how brightness changes across different wavelengths—matched expectations for a star cluster, suggesting that Earendel could indeed be a collection of stars rather than a single entity.

Despite these compelling findings, not all astronomers are convinced. Brian Welch, a postdoctoral researcher at the University of Maryland and one of the original discoverers of Earendel, cautioned that the spectral data alone may not definitively classify the object as a star cluster. “At the spectral resolution of the NIRSpec, the spectrum of a lensed star and a star cluster can be very similar,” he noted, emphasizing the need for comprehensive analysis that considers all potential scenarios.

To further unravel the mystery of Earendel, both Pascale and Welch agree that monitoring microlensing effects will be crucial. Microlensing occurs when a passing object distorts the image of a distant object, providing a unique opportunity to study smaller celestial bodies like stars or planets.

As the scientific community eagerly anticipates future observations from the JWST, the possibility of Earendel being a star cluster opens new avenues for understanding the formation and evolution of stars in the early universe. With each new discovery, we move closer to unveiling the secrets of our cosmos, and Earendel stands at the forefront of this exciting journey.