This immense celestial object, nicknamed the “behemoth star,” is estimated to be more than 2,000 times the size of our Sun.
For the first time in human history, a star in a galaxy beyond the Milky Way has been imaged in extraordinary detail. Keiichi Ohnaka, an astrophysicist from the Universidad Andrés Bello in Chile, achieved this milestone using the unparalleled capabilities of the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI). The star, known as WOH G64, resides in the Large Magellanic Cloud, a satellite galaxy of our Milky Way, over 160,000 light-years away.
This immense celestial object, nicknamed the “behemoth star,” is estimated to be more than 2,000 times the size of our Sun. According to Ohnaka, WOH G64 is in its final stages of life, preparing for an eventual supernova explosion. Surrounding the star is an egg-shaped cocoon of gas and dust—an unusual feature that has intrigued researchers.
“For the first time, we have succeeded in taking a zoomed-in image of a dying star in a galaxy outside our own Milky Way,” Ohnaka stated, emphasizing the significance of capturing this rare moment.
Decades of Research Culminate in GRAVITY’s Triumph
The road to this breakthrough began in 2005 when Ohnaka and his team initiated studies on WOH G64. Despite uncovering valuable insights, their attempts to capture a detailed image were thwarted by technological limitations. Everything changed in 2015 with the introduction of GRAVITY, a second-generation instrument at ESO’s VLTI.
“GRAVITY is born from the desire to observe very small details of faint objects,” explains Xavier Haubois, an ESO astronomer. This revolutionary tool gathers light from multiple telescopes with remarkable sensitivity, enabling the imaging of distant stars, galactic centers, and exoplanets in unprecedented detail.
Once GRAVITY was operational, Ohnaka’s team turned their focus back to the behemoth star. The enhanced instrument successfully captured enough light to produce the first close-up image of a star in another galaxy. The new data revealed significant changes in WOH G64, including noticeable dimming over the last decade, a hallmark of a dying star.
“This provides us with a rare opportunity to witness a star’s life in real-time,” noted Gerd Weigelt, a co-author of the study and professor at the Max Planck Institute for Radio Astronomy.
Unraveling the Mysteries of a Behemoth Star
One of the most unexpected discoveries was the irregular shape of the surrounding gas cloud. While theoretical models predicted a symmetrical structure, the egg-like shape points to unusual dynamics, potentially influenced by gas shedding or an undetected companion star.
Despite these revelations, the star’s final fate remains uncertain. While its dimming signals the shedding of outer layers, its demise as a supernova may still be thousands of years away. However, as Jacco van Loon from Keele University cautioned, any abrupt change in its dynamics could hasten its explosive end.
“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 explained.
The Future of GRAVITY and Beyond
The historic image marks just the beginning. ESO’s plans to upgrade GRAVITY with cutting-edge adaptive optics, under the GRAVITY+ project, promise even more groundbreaking discoveries. These advancements will refine the correction of atmospheric blurring, enhance contrast, and improve tracking capabilities, opening new frontiers for the study of distant galaxies, exoplanets, and even the mysterious black hole at the center of our galaxy, Sagittarius A*.
“The upgrade will enable the discovery and characterization of exoplanets, the imaging of young stars and their protoplanetary disks, and the search for intermediate-mass black holes,” according to ESO’s project team.