Earendel, The Most Distant Star, May Not Be a Star After All, New Study Reveals

The James Webb Space Telescope (JWST) has delivered an unexpected twist in the case of Earendel, the most distant star ever discovered. Previously believed to be a singular, massive star located 12.9 billion light-years away, Earendel’s true nature is now under scrutiny. A recent study, published in The Astrophysical Journal, suggests that Earendel may not be a single star at all. Instead, it could be a star cluster — a group of stars bound together by gravity and formed from the same gas and dust cloud. This revelation comes after astronomers, using the advanced capabilities of the JWST, observed this ancient cosmic object in more detail, raising questions about its classification and how early star clusters might have looked during the universe’s first billion years.

The discovery of Earendel by the Hubble Space Telescope in 2022 was a monumental moment for astronomy. This star seemed to be forming just 900 million years after the Big Bang, during a period when the universe was a mere fraction of its current age. However, the observations made with the JWST have unveiled a new possibility: Earendel could be a compact globular star cluster, a type of stellar group found in the present-day universe. Researchers now suggest that the characteristics of Earendel’s light are consistent with those of such clusters, which were once thought to have formed in the early stages of the universe’s evolution. But the study is far from conclusive, and some experts believe further analysis is needed before this hypothesis can be confirmed.

A Fresh Look With the JWST

When Earendel was first observed, the Hubble Space Telescope’s data suggested it might be a massive individual star. At the time, astronomers believed it to be a stellar beacon shining with about a million times the luminosity of the Sun. However, new spectroscopic data from the JWST’s Near Infrared Spectrograph (NIRSpec) instrument offers a more nuanced view. The JWST’s highly sensitive tools allowed researchers to scrutinize the light emitted from Earendel, looking for subtle patterns in its spectral features. What they found was a match to the light emitted by globular clusters — groups of stars that are much older and denser than typical stellar systems.

“What’s reassuring about this work is that if Earendel really is a star cluster, it isn’t unexpected!” Massimo Pascale, an astronomy doctoral student at the University of California, Berkeley, and lead author of the study, told Live Science in an email. “[This] work finds that Earendel seems fairly consistent with how we expect globular clusters we see in the local universe would have looked in the first billion years of the universe.”

Gravitational Lensing and Earendel’s Discovery

Earendel’s extreme distance made it incredibly difficult to observe. Fortunately, astronomers leveraged gravitational lensing, a phenomenon predicted by Einstein’s theory of general relativity. This occurs when massive objects like galaxy clusters bend and magnify the light from objects behind them, much like a cosmic magnifying glass. In the case of Earendel, a massive galaxy cluster positioned between Earth and the distant star allowed it to be observed in exceptional detail. Without this gravitational lensing effect, Earendel’s light would have been too faint to detect with current technology.

In addition to magnifying Earendel’s light by a factor of 4,000, the lensing effect made it appear much larger than it would have appeared in its original form. This distortion prompted astronomers to question whether Earendel was a single star or something more complex. Such rare alignments of cosmic objects, though extremely valuable for studying distant objects, also pose challenges in terms of accurately interpreting the data. As the research progressed, it became clear that a new hypothesis — that Earendel might be a star cluster — deserved closer inspection.

Exploring the Star Cluster Hypothesis

The shift in thinking regarding Earendel’s nature stems from the study’s findings on its age and metal content. The light spectrum revealed by the JWST’s instruments indicated that Earendel’s properties closely resemble those of globular clusters found in the local universe. Globular clusters are ancient structures composed of hundreds of thousands of stars that are all formed from the same material. They are characterized by their compactness, old age, and high density, which fit with what astronomers now believe to be true of Earendel.

“After some recent work showed that indeed Earendel could (but is not necessarily) be much larger than previously thought, I was convinced it was worthwhile to explore the star cluster scenario,” Pascale said. His team’s findings indicated that the object’s size and composition could be consistent with a star cluster, potentially an ancient one from the universe’s infancy.

Challenges in the Study: A Speculative Future

While the new data provides some support for the star cluster hypothesis, the study is not definitive. Brian Welch, a postdoctoral researcher at the University of Maryland and NASA Goddard Space Flight Center, played a key role in discovering Earendel using the Hubble Space Telescope in 2022. Although not involved in the current study, Welch noted that the spectral data gathered by the JWST might not be enough to conclusively identify Earendel as a star cluster. “At the spectral resolution of the NIRSpec [instrument], the spectrum of a lensed star and a star cluster can be very similar,” Welch said. “It is therefore important to consider all available data when attempting to classify these highly magnified objects.”

Welch also emphasized that by focusing solely on the star cluster hypothesis, the research team may have limited the scope of the investigation. The study does not fully explore other potential explanations for Earendel’s strange characteristics, such as the possibility that it could be a binary system or an entirely different type of cosmic object. “The measurement is robust and well done, but in only considering the star cluster hypothesis, the study is limited in scope,” he added.

What’s Next for Earendel?

The debate surrounding Earendel’s true identity is far from over. Both Pascale and Welch agree that monitoring changes in the object’s brightness could provide critical clues about its nature. Microlensing — a phenomenon that occurs when smaller objects temporarily distort the light from distant stars — could offer insight into whether Earendel is a star or a cluster of stars. Microlensing effects are more pronounced in smaller objects, which would help distinguish whether the object is a single star or a cluster.

“It will be exciting to see what future JWST programs could do to further demystify the nature of Earendel,” Pascale said, hinting that further exploration could eventually resolve the puzzle surrounding this mysterious object.