Left: Image of the star WOH G64 taken with the Very Large Telescope Interferometer in Chile. Right: Artist’s impression of a star
ESO/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. Massive stars may be showing signs that they are only a few years away from exploding, a process we have never seen in detail.
The largest stars we know of are red supergiants whose cores have run out of hydrogen fuel. Instead, the shell of hydrogen gas surrounding the core burns, causing the star to expand enormously.
One of the largest red supergiants we know of is WOH G64, sometimes also called a giant star. This star is between 1540 and 2575 times the size of the Sun and is located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy. This star has been a target of astronomers since its discovery in the 1970s, but it is difficult to observe in detail because it is too far away.
now, Jaco van Loon Keele University, UK, and colleagues took close-up pictures of WOH G64 using the Very Large Telescope interferometer in Chile’s Atacama Desert. meter telescope. “In this image we can see details like seeing an astronaut walking on the moon,” says van Loon. “You can’t see it with a regular telescope pointed at the moon.”
This image, taken using infrared light, shows a bright ball of gas and dust hotter than 1000°C (1832°F). This ball has spewed out stars and now surrounds itself like a dense cocoon. “This is actually a structure we never expected to see in practice,” says van Loon. “We were hoping to see a star in the middle.”
Van Loon said the gas and dust may have appeared relatively recently because the star is dimmer than when it was last observed. It may have been created by blowing away the outer layers of a star that astronomers have never captured in a red supergiant.
If that happens, and the process is similar to that seen in similar stars called blue supergiants, it could be a sign that the star is decades or even years away from exploding. “If we can see this star exploding, we can get a lot more details about the star before it exploded,” says van Loon.
“It is technically very impressive to be able to reconstruct an image of this object taking into account the extreme distances,” he says. paul crowder from the University of Sheffield, UK.
However, it is difficult to say for sure whether the observed gas and dust, and the associated decrease in brightness, are signs of an impending explosion. “Stars like this object are well known to be highly variable,” Crowther says. “This is simply what happens in celestial bodies with dense, slow outflows not too far from stars. “It’s well known as a dust factory.”
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