Astronomers have, for the first time ever, captured a close-up image of a star beyond our home Galaxy.
The star, known as WOH G64, is located 160,000 lightyears away in the Large Magellanic Cloud, a small satellite galaxy of our own Milky Way.
Zoomed-in images of stars within our Galaxy have been captured before, but this marks the first ever detailed image of a star in a different galaxy.
Astronomers have known about WOH G64 for decades, and it's referred to as the ‘behemoth star’.
It's about 2,000 times the mass of our Sun and is a type of star known as a red supergiant.
One galaxy of many
It's only relatively recently that astronomers confirmed our Milky Way galaxy was just one of many throughout the Universe.
In the early 20th century, Edwin Hubble was able to confirm that an observed star was located beyond the domain of our home Galaxy.
And just like Nicholas Copernicus's revelation that our planet was just one among many orbiting the Sun, Hubble's discovery ultimately changed our view of the Universe.
Studying distant galaxies - and stars within those distant galaxies - is a key part of understanding the cosmos around us.
Discovering WOH G64
"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," says Keiichi Ohnaka, an astrophysicist from Universidad Andrés Bello in Chile.
WOH G64 was imaged using the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI).
The observations reveal that the star is in the final stages of its life, expanding outwards in a shell of gas and dust just before it explodes as a supernova.
"We discovered an egg-shaped cocoon closely surrounding the star," says Ohnaka, lead author of the study published in Astronomy & Astrophysics.
"We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion."
Ohnaka and the team first observed WOH G64 back in 2005 and 2007 using ESO’s VLTI in Chile’s Atacama Desert.
But it was the development of the VLTI’s GRAVITY instrument that has made this new image possible.
The observations reveal that the star has become dimmer over the past decade.
"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," says Gerd Weigelt, astronomy professor at the Max Planck Institute for Radio Astronomy in Bonn, Germany and a co-author of the study.
A star at the end of its life
Red supergiants like WOH G64 are stars going through the final stages of their life, shedding their outer layers of gas and dust.
"This star is one of the most extreme of its kind, and any drastic change may bring it closer to an explosive end," says co-author Jacco van Loon, Keele Observatory Director at Keele University, UK, who has been observing WOH G64 since the 1990s.
This shedding of material may be the reason why the star is appearing to dim, and also could explain the strange shape of the dusty cocoon surrounding it.
The image captured by the astronomers shows the cocoon is stretched-out, which could be explained by the shedding or may suggest a companion star that's not been seen yet.
"Similar follow-up observations with ESO instruments will be important for understanding what is going on in the star," says Ohnaka.
