VLTI Captures Detailed Image of Red Supergiant in Large Magellanic Cloud

Astronomers using ESO’s Very Large Telescope Interferometer (VLTI) have captured a zoomed-in image of the dust-enshrouded red supergiant star WOH G64.

WOH G64 is located approximately 160,000 light-years away in the constellation of Dorado.

Also known as IRAS 04553-6825, 2MASS J04551048-6820298 or TIC 30186593, the star is part of the Large Magellanic Cloud, one of the small galaxies that orbits our Milky Way Galaxy.

With a size roughly 2,000 times that of our Sun, WOH G64 is classified as a red supergiant.

“We discovered an egg-shaped cocoon closely surrounding the star,” said Dr. Keiichi Ohnaka, an astrophysicist at the Universidad Andrés Bello.

“We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion.”

“While astronomers have taken about two dozen zoomed-in images of stars in our Milky Way Galaxy, unveiling their properties, countless other stars dwell within other galaxies, so far away that observing even one of them in detail has been extremely challenging — up until now.”

Dr. Ohnaka and colleagues had long been interested in WOH G64.

Back in 2005 and 2007, they used VLTI to learn more about the star’s features, and carried on studying it in the years since. But an actual image of the star had remained elusive.

For the desired picture, they had to wait for the development of one of the VLTI’s second-generation instruments, GRAVITY.

After comparing their new results with other previous observations of WOH G64, they were surprised to find that the star had become dimmer 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 Professor Gerd Weigelt, an astronomer at the Max Planck Institute for Radio Astronomy.

In their final life stages, red supergiants like WOH G64 shed their outer layers of gas and dust in a process that can last thousands of years.

“This star is one of the most extreme of its kind, and any drastic change may bring it closer to an explosive end,” said Dr. Jacco van Loon, director of Keele Observatory at Keele University.

“These shed materials may also be responsible for the dimming and for the unexpected shape of the dust cocoon around the star,” the astronomers said.

The new image shows that the cocoon is stretched-out, which surprised the researchers, who expected a different shape based on previous observations and computer models.

They believe that the cocoon’s egg-like shape could be explained by either the star’s shedding or by the influence of a yet-undiscovered companion star.

As the star becomes fainter, taking other close-up pictures of it is becoming increasingly difficult, even for VLTI.

Nonetheless, planned updates to the telescope’s instrumentation, such as the future GRAVITY+, promise to change this soon.

“Similar follow-up observations with ESO instruments will be important for understanding what is going on in the star,” Dr. Ohnaka said.

The team’s paper was published in the journal Astronomy & Astrophysics.

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K. Ohnaka et al. 2024. Imaging the innermost circumstellar environment of the red supergiant WOH G64 in the Large Magellanic Cloud. A&A 691, L15; doi: 10.1051/0004-6361/202451820