What appears as a single point of light might actually be multiple bright stars
Desde las profundidades del cosmos, un objeto descubierto hace apenas tres años vuelve a plantear preguntas que la ciencia creía haber respondido. Eärendel, la señal más lejana jamás detectada, emergió cuando el universo tenía menos de mil millones de años, y lo que Hubble interpretó como una estrella solitaria podría ser, según el James Webb, un cúmulo compacto de estrellas antiguas. En la astronomía, como en tantas disciplinas humanas, cada respuesta abre una puerta hacia una incertidumbre más profunda y más rica.
- Lo que parecía ser un hito definitivo —la estrella más lejana jamás observada— está siendo cuestionado por el mismo avance tecnológico que debía confirmarlo.
- El instrumento NIRSpec del James Webb detectó un patrón de luz más compatible con un cúmulo globular que con una estrella individual, sacudiendo la clasificación original de Hubble.
- Dos visiones científicas se enfrentan: quienes ven en los nuevos datos una reinterpretación coherente con la formación temprana del universo, y quienes advierten que las firmas espectrales de ambos fenómenos pueden ser indistinguibles.
- El debate no tiene resolución inmediata: se necesitan nuevas observaciones, especialmente sensibles a efectos de microlente gravitacional, para determinar si Eärendel es una o muchas estrellas.
- Independientemente del resultado, el objeto sigue siendo una ventana extraordinaria hacia el universo en su primera infancia, hace 12.900 millones de años.
Tres años después de que el Hubble identificara a Eärendel como el objeto más lejano jamás observado, los astrónomos se preguntan si realmente estaban mirando una sola estrella. Surgido apenas 900 millones de años después del Big Bang, Eärendel fue posible de detectar gracias al lente gravitacional de galaxias intermedias, que amplificaron su luz más de 4.000 veces. La teoría inicial sostenía que era una estrella única, extraordinariamente caliente y luminosa, ubicada en la galaxia Arco del Amanecer, a 12.900 millones de años luz de la Tierra.
Ahora, datos espectroscópicos del James Webb publicados en The Astrophysical Journal sugieren otra posibilidad. El instrumento NIRSpec analizó el comportamiento de la luz de Eärendel en distintas longitudes de onda, y el patrón observado se asemeja más al de un cúmulo globular —una esfera densa de estrellas antiguas— que al de un astro solitario. El investigador Massimo Pascale señaló que esta reinterpretación encajaría bien con lo que se esperaría de un cúmulo globular en los primeros mil millones de años del universo.
Sin embargo, el astrónomo Brian Welch, uno de los descubridores originales de Eärendel, advirtió que la evidencia espectroscópica no es concluyente: la firma luminosa de una estrella lensada y la de un cúmulo pueden ser notablemente similares a la resolución actual. Resolver el enigma requerirá observaciones adicionales, especialmente orientadas a detectar efectos de microlente gravitacional. Eärendel, estrella o cúmulo, sigue siendo un testimonio invaluable del universo en su más temprana juventud.
Three years after the Hubble Space Telescope spotted what appeared to be the most distant object ever observed in the universe, astronomers are now questioning whether they were looking at a single star at all. The object, named Eärendel, emerged from the cosmic fog just 900 million years after the Big Bang—a moment when the universe was still in its infancy. But fresh analysis from the James Webb Space Telescope suggests Eärendel might not be the solitary beacon astronomers thought it was. Instead, it could be a compact cluster of stars, bound together by gravity and born from the same cloud of gas and dust billions of years ago.
When Hubble first identified Eärendel in 2022, the prevailing theory held that it was an extraordinarily hot and luminous single star. The object sits in the Arco del Amanecer galaxy, roughly 12.9 billion light-years from Earth—so distant that its light has been traveling toward us since the universe was young. What made observation possible at all was gravitational lensing, a phenomenon predicted by Einstein's theory of relativity. Massive galaxies between us and Eärendel bend and magnify its light like a cosmic lens, amplifying the object's image by more than 4,000 times. Without this natural magnification, Eärendel would be far too faint to detect.
The James Webb telescope's new spectroscopic data, published in The Astrophysical Journal, tells a different story. Researchers used the instrument called NIRSpec to examine how Eärendel's light behaves across different wavelengths. The brightness pattern they observed matched what astronomers see in globular clusters—dense groupings of stars that exist throughout our galaxy and others nearby. These are not the sprawling spiral galaxies we know, but rather tightly packed spheres of ancient stars, sometimes containing hundreds of thousands of members.
Massimo Pascale, a researcher at the University of California, noted that this reinterpretation, while significant, is not entirely unexpected. If Eärendel truly is a star cluster, it fits neatly with what astronomers would predict for a globular cluster during the universe's first billion years. The new data suggest that what appears as a single point of light from Earth might actually be multiple bright stars clustered so closely together that they blur into one luminous source.
Yet the mystery remains unsolved. Brian Welch, one of the astronomers who discovered Eärendel with Hubble, cautioned that the spectroscopic evidence alone cannot definitively settle the question. The light signature of a single lensed star and the combined light of a star cluster can look remarkably similar when viewed at the resolution that NIRSpec provides. Welch emphasized that resolving this debate will require additional observations, particularly those sensitive to microlensing effects—subtle variations in how gravity bends light from different parts of the object.
What began as a triumph of detection—finding the most distant object ever seen—has become a puzzle about interpretation. Eärendel remains ancient and remarkable either way, a window into the universe when it was barely a billion years old. But whether it is one star or many, the object continues to challenge astronomers' understanding of how massive objects formed in the early cosmos. More observations will come, and with them, perhaps, clarity about what Eärendel truly is.
Citações Notáveis
If Eärendel really is a star cluster, it is not unexpected— Massimo Pascale, University of California researcher
The spectrum of a lensed star and a cluster of stars can be very similar at NIRSpec's spectral resolution— Brian Welch, original Eärendel discoverer
A Conversa do Hearth Outra perspectiva sobre a história
So we thought we found the most distant star, and now it might not be a star at all?
Right. Hubble saw what looked like a single, incredibly bright object in 2022. But when Webb looked at it more carefully—at how the light behaves across different wavelengths—the pattern matched what we see in star clusters, not individual stars.
How can you confuse a star cluster with a single star? Aren't they obviously different?
Not when they're 12.9 billion light-years away and magnified by gravitational lensing. The cluster is so compact and so far away that it appears as one point of light. Webb's instruments can see more detail, but even then, the spectral signatures are ambiguous.
So we still don't know what it is?
Not for certain. One of the original discoverers, Brian Welch, said the current data can't rule out either possibility. A lensed single star and a cluster can look nearly identical at this resolution. We'd need different kinds of observations—microlensing studies—to tell them apart.
Does it matter? Either way, it's ancient.
It does matter. A single star that bright would tell us something different about stellar formation in the early universe than a cluster would. The physics is different. And it's a reminder that even our best telescopes can deceive us when we're looking at the edge of the observable universe.