Scientists have successfully captured the first detailed image of a dying star outside our Milky Way galaxy, wrapped in a strange, egg-shaped cocoon. The star, identified as WOH G64, is located 160,000 light-years from us in the Large Magellanic Cloud and is surrounded by a plume of gas and dust — suggesting it was in the final stage of its life. During a star’s last phase, it transforms into a red supergiant before dying in a huge cosmic explosion, known as a supernova.
“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,” said Keiichi Ohnaka, an astrophysicist from Universidad Andrés Bello in Chile and the lead author of the study.
WOH G64 was captured using the GRAVITY instrument at the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI). With a size roughly 2000 times that of our Sun, WOH G64 provides insights into the lifecycle of a star and how it goes out with a fascinating bang.
“We discovered an egg-shaped cocoon closely surrounding the star. We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion,” Mr Ohnaka added.
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Years of research
Scientists have been interested in the red supergiant for nearly two decades. In 2005 and 2007, Mr Ohnaka and his team used ESO’s VLTI in Chile’s Atacama Desert to learn more about the star’s features and carried on studying it in the years since. However, an actual image of the star remained elusive. To click the first, detailed image, the team had to wait for the development of one of the VLTI’s second-generation instruments.
“Massive stars explode with an energy equivalent to the Sun shining for all of its 10 billion years of life. People have seen these supernova explosions, and astronomers have found some of the stars that exploded in older images. But we have never seen a star change in a way that signals its imminent death.”
The researchers believe that the gas and dust around the star, also known as shed material, might be responsible for the dimming and for the unexpected shape of the cocoon around the star. The new image shows that the cocoon is stretched out, which surprised scientists, who expected a different shape based on previous observations and computer models.
The team believes 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.