PREVIEW

For the first time, scientists have obtained a detailed image of a dying star located outside our own Milky Way galaxy.

Keiichi Ohnaka, an astrophysicist at Universidad Andrés Bello in Chile, announced the breakthrough, made possible by the exceptional capabilities of the European Southern Observatory’s Very Large Telescope Interferometer (VLTI).

The star, known as WOH G64, lies in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, roughly 160,000 light-years away. It has been identified as a red supergiant approximately 2,000 times the size of our Sun.

“This is a major step forward,” said Dr Ohnaka. “We discovered an egg-shaped cocoon of gas and dust closely surrounding the star. This may be linked to the violent ejection of material that occurs in the final stages of a star’s life before it explodes as a supernova.”
Astronomers have previously obtained close-up images of stars within the Milky Way, but observing individual stars in other galaxies has posed significant challenges due to their vast distances. The VLTI’s advanced GRAVITY instrument enabled researchers to capture the unprecedented image of WOH G64.

Dr Gerd Weigelt, a co-author from the Max Planck Institute for Radio Astronomy, highlighted the star’s dramatic changes over the last decade: “WOH G64 has dimmed significantly, giving us a rare opportunity to observe a star’s life unfolding in real time.”
The findings suggest that the dimming may be due to material shed by the star. This ejected matter forms the surrounding cocoon, whose unexpected egg-like shape has puzzled researchers.

The team hypothesises that either the shedding process or the gravitational influence of an undiscovered companion star may explain the cocoon’s shape.

Red supergiants like WOH G64 shed their outer layers of gas and dust over thousands of years before collapsing in a supernova.

Dr Jacco van Loon, director of Keele Observatory in the UK and a long-time observer of WOH G64, remarked, “This star is one of the most extreme of its kind, and its rapid changes might be bringing it closer to an explosive finale.”

Although capturing further images of WOH G64 is becoming increasingly difficult due to its dimming, planned upgrades to the VLTI, such as GRAVITY+, offer hope for deeper observations in the near future.

The VLTI, located in Chile’s Atacama Desert, combines light from four 8-metre telescopes to achieve extraordinary resolution, creating what is effectively a virtual telescope with unprecedented detail. GRAVITY, the second-generation instrument used in this study, significantly advanced the imaging capabilities, enabling the first close-up view of WOH G64.
ESO’s efforts to develop next-generation instruments, including GRAVITY+, will expand the frontiers of astronomical observation, allowing scientists to study even fainter and more distant objects.

The research, published in Astronomy & Astrophysics, involved an international team led by Dr Ohnaka and included experts from institutions in Germany, the UK, and the USA. The study exemplifies the collaborative spirit of the European Southern Observatory, whose facilities in Chile continue to make ground-breaking discoveries possible.