MADRID, 19 (EUROPA PRESS)
Eärendel, an object discovered in 2022 with the James Webb Space Telescope and considered the most distant star known, may actually be a star cluster.
Upon its discovery, Eärendel was thought to be a star that formed just 900 million years after the Big Bang, when the universe was only 7% of its current age.
Now, in a study published in The Astrophysical Journal, astronomers have again used the James Webb telescope to explore the possibility that Eärendel is not a single star or a binary system , as previously thought, but a compact star cluster.
They found that Eärendel's spectral characteristics match those of globular clusters—a type of star cluster—present in the local universe.
“What’s reassuring about this work is that if Eärendel is indeed a star cluster, it’s not unexpected!” Massimo Pascale, a doctoral student in astronomy at the University of California, Berkeley, and lead author of the study, told Live Science. “This work reveals that Eärendel seems quite consistent with how we expect the globular clusters we observe in the local universe to have appeared during the first billion years of the universe.”
Eärendel, located in the Dawn Arc Galaxy, 12.9 billion light-years away, was discovered to be subject to gravitational lensing, a phenomenon predicted by Einstein's theory of general relativity, in which massive objects bend the light passing around them. A massive galaxy cluster located between Earth and Eärendel, it is so large that it distorts the fabric of space-time, creating a magnifying effect that allowed astronomers to observe light from Eärendel, which would otherwise be too faint to detect. Studies indicate that the star appears at least 4,000 times larger due to this gravitational lensing effect.
This magnification is greatest in certain special regions. If a star or galaxy is located right next to one of these regions, its image can appear hundreds or thousands of times brighter than normal. Eärendel appears to be extremely close to one of these sweet spots, which is why we can see it despite being nearly 12.9 billion light-years away. These near-perfect alignments are incredibly rare, leading astronomers to consider alternative explanations beyond a single star.
SIGNS OF A COLDER COMPANION
Following Eärendel's discovery in 2022, researchers analyzed the object using data from the James Webb Near-Infrared Imaging Camera (NIRCam). By examining its brightness and size, they concluded that Eärendel could be a massive star, more than twice as hot as the Sun and about a million times more luminous than our star. Astronomers also found in Eärendel's color a hint of the presence of a cooler companion star.
"After recent work showed that Eärendel could (though not necessarily) be much larger than previously thought, I became convinced that the star cluster scenario was worth exploring," Pascale said.
Using spectroscopic data from JWST's NIRSpec instruments, Pascale and her team studied Eärendel's age and metal content.
The team analyzed Eärendel's spectroscopic continuum, which essentially shows how its brightness changes smoothly across different wavelengths of light. This pattern matched what would be expected from a star cluster and, at the very least, the combined light from several stars.
The researchers only explored the possibility of a "star cluster." They didn't investigate all possible scenarios, such as Earendel being a single star or a multiple star system, nor did they compare the results.
