Left: An image of the star WOH G64 taken with the Very Large Telescope Interferometer in Chile. Right: An artist’s impression of the star
IT/K. Ohnaka et al., L. Calçada
Astronomers have taken the first detailed picture of a star in another galaxy, more than 160,000 light years away. They may be signs that giant stars are years away from exploding, a process we’ve never seen in detail.
The largest known stars are red supergiants, which are stars that have run out of hydrogen fuel in their cores. Instead, a shell of hydrogen gas surrounding the core burns, massively expanding the star’s volume.
One of the largest known red supergiants is WOH G64, sometimes called a behemoth star. It is between 1540 and 2575 times the size of the Sun and resides in a satellite galaxy of the Milky Way. Large Magellanic Cloud. The star has been a target for astronomers since its discovery in the 1970s, but its distance is difficult to study closely.
now, Jacco van Loon Keele University in the UK and colleagues have taken a close-up picture of WOH G64 using the Very Large Telescope Interferometer in Chile’s Atacama Desert, a collection of four individual telescopes linked together to function as one of 200. metro telescope “In this image, we can see details that would be equivalent to seeing an astronaut walking on the moon,” says van Loon. “You can’t see that through an ordinary telescope pointed at the moon.”
The image, taken using infrared light, shows a glowing ball of gas and dust, more than 1000°C (1832°F), that has been ejected by the star and now surrounds it as a dense cocoon. “It’s a structure we didn’t really expect to see,” says van Loon. “We were just hoping to see the star in the middle.”
The star appears dimmer than when it was last observed, so the gas and dust likely appeared recently, says van Loon. It may have formed when the star exploded its outer layers, which astronomers have never caught before in a red supergiant.
If this happened and the process resembles what is seen in similar stars called blue supergiants, then it could be a sign that the star is decades or years away from exploding. “If we see this star exploding, we have much more detail about a star before it explodes than ever before,” says van Loon.
“It’s technically very impressive to be able to reconstruct an image of this object given its extreme distance,” he says. Paul Crowther at the University of Sheffield, United Kingdom.
However, it is more difficult to say for sure whether the observed gas and dust, and the associated dimming of the glow, are signs of an imminent explosion. “Stars like this object are known to be highly variable,” says Crowther. “It’s just what happens in these objects, where they have this dense, slow outflow that doesn’t go very far from the stars. They are known to be dust factories.’
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