Astronomers have captured a close-up image of a dying star in a galaxy beyond our own—the first time this has ever been achieved.
The star, WOH G64, is in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, approximately 160,000 light-years away.
"This is the first time we actually have a sharp image of a star in another galaxy," said Jacco van Loon, director of the U.K.'s Keele Observatory, who has observed WOH G64 for decades.
"What we have been able to see here is very hot dust that has freshly formed close to the star because of some kind of eruption. We didn't know we were going to find this," Van Loon told Newsweek.
The star, known as a red supergiant, is roughly 2,000 times the size of our sun and has long fascinated astronomers because of its immense size and peculiar characteristics.
The new observations, detailed in the journal Astronomy & Astrophysics, show WOH G64 is surrounded by a distinctive, egg-shaped cocoon of gas and dust, a hallmark of a star nearing the end of its life.
"We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion," said Keiichi Ohnaka, an astrophysicist at Chile's Universidad Andrés Bello who led the study, in a statement.
Such observations could provide insights into the final stages of stellar evolution and the processes leading to supernovas.
WOH G64 has been nicknamed the "behemoth star" because of its extraordinary size and luminosity. This made it the ideal candidate for the first close-up image of a star outside our galaxy.
Astronomers have known about it for decades, but until now capturing a detailed image was not possible. The breakthrough came thanks to the GRAVITY instrument on the European Southern Observatory's Very Large Telescope Interferometer, which provided the unprecedented sharpness needed to image the distant star.
Van Loon said the telescope is so powerful that it could distinguish a person walking on the surface of the moon.
Comparing their latest findings to previous studies, the team was surprised to discover that WOH G64 had dimmed significantly over the past decade.
"We have found that the star has been experiencing a significant change in the last 10 years, providing us with a rare opportunity to witness a star's life in real time," said Gerd Weigelt, a professor at Germany's Max Planck Institute for Radio Astronomy and a co-author of the study, in the statement.
Red supergiants like WOH G64 are known to shed their outer layers in dramatic displays as they approach their explosive end.
These materials often form dense clouds around the star, and, in this case, they seem to explain both the dimming and the peculiar egglike shape of the surrounding cocoon. Scientists speculate that the shape could also hint at the influence of an undiscovered companion star.
While approximately two dozen zoomed-in images of stars within our galaxy have been captured, studying individual stars in other galaxies has remained an extraordinary challenge until now.
"This is the first but only the first of many to follow," Van Loon said. With new instruments and telescopes coming online in recent years, he predicted that more extragalactic stars would be imaged—and possibly even planets orbiting stars in other galaxies.
"This star is one of the most extreme of its kind, and any drastic change may bring it closer to an explosive end," Van Loon said in the statement.
As WOH G64 approaches its inevitable supernova, astronomers will continue monitoring it closely, eager to witness what could be one of the most dramatic events in the cosmos.
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Reference
Ohnaka, K., Hofmann, K.-H., Weigelt, G., Van Loon, J. Th., Schertl, D., & Goldman, S. R. (2024). Imaging the innermost circumstellar environment of the red supergiant WOH G64 in the Large Magellanic Cloud. Astronomy & Astrophysics. https://doi.org/10.1051/0004-6361/202451820
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