One of the largest known stars in the universe underwent a dramatic change in 2014 and may be preparing to explode, a new study has revealed.
A study published today in Nature Astronomy and led by Gonzalo Muñoz Sánchez of the National Observatory of Athens claims that the giant star WOH G64 has transitioned from a red supergiant to a rare yellow supergiant, which could be evidence of an impending supernova explosion.
Evidence suggests that in real time, we may be witnessing a massive star shedding its outer layers, shrinking as it heats up and nearing the end of its short lifespan.
very special star
WOH G64 was first discovered in the 1970s as a featured star in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way.
They found that the star was not only extremely bright, but also one of the largest ever discovered, with a size more than 1,500 times the radius of the Sun.
In 2024, WOH G64 became the first extragalactic star ever imaged in detail thanks to the Very Large Telescope Interferometer. The image clearly shows a dusty cocoon surrounding the central giant star, confirming that it is losing mass as it ages.
From super gigantic to super gigantic, big is big
WOH G64 is a young star in the grand scheme of the universe, with an estimated age of less than 5 million years. Unlike our Sun (currently about 4.6 billion years old), WOH G64 is destined to live fast and die young.
WOH G64 was formed from a huge cloud of gas and dust that collapsed under pressure until it ignited. Like our sun, nuclear fusion would have burned hydrogen in its core.
It would then have expanded and burned up helium, becoming a so-called red supergiant star.
Not all supergiants become supergiants. Supergiants are theorized to form when very large stars rapidly burn and evolve from burning hydrogen to burning helium.
During this transition, these stars begin to shed their outer layers, while their cores begin to shrink inward. When a star becomes a supergiant, it is doomed to die quickly in the violent explosion of a supernova.
What caused this change seen in WOH G64?
So what happened to WOH G64 in 2014? A new study proposes that much of the former supergiant’s surface was ejected from the star.
This may be due to an interaction with a companion star, which the authors confirmed by observing the spectrum of light from WOH G64.
Another theory is that the star is preparing to explode. We know that a star this big is bound to make a big splash, but it can be hard to tell in advance when that will happen.
One possible scenario is that the transition we’re seeing is due to a pre-supernova “superwind” phase. This is theorized to occur due to strong internal pulsations as fuel in the reactor core is rapidly consumed.
Only time will tell
Most stars live for tens of millions of years, even tens of billions of years. We could never have predicted that we would be able to witness and record so many changes in stars outside our galaxy.
If we are lucky, we will see the death of WOH G64 in our lifetime. In addition to providing an incredible intergalactic spectacle, it will also help scientists complete this fascinating star puzzle.
Sara Webb, Lecturer, Center for Astrophysics and Supercomputing Swinburne University of Technology
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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