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Illustration of the binary star system WOH G64 surrounded by a dense ring of dust. |Image credit: Daniel Seia Martinez
Astronomers have witnessed one of the largest stars in the universe transform into a rare stellar body, a dramatic transformation that may have been a prequel to the powerful supernova explosion that birthed a black hole from the star.
doomed Star The one in question is WOH G64 (also known as IRAS 04553–6825), located in Milky Way called Large Magellanic Cloud (LMC), about 163,000 light-years away. The star is about 1,540 times larger sunwhich is almost 30 times more massive than our star and an astonishing 282,000 times brighter. WOH G64 was discovered in the 1970s and has been considered red supergiant The star is surrounded by a ring or torus of dense dust.
However, by 2014, the appearance of this superstar began to change. A team of astronomers led by Gonzalo Muñoz Sánchez of the National Observatory of Athens noticed that the star’s color changed with a corresponding increase in its surface temperature. Muñoz-Sanchez and colleagues determined that this must represent the transformation of a red supergiant into a rare yellow supergiant, which could also mean astronomers are witnessing the death of a star in real time.
“The fate of stars with initial masses between 23 and 30 solar masses after evolving into red supergiants remains uncertain. In this case, WOH G64 is the most extreme red supergiant known, with an estimated mass of about 28 solar masses,” Muñoz-Sanchez told Space.com. “It’s unclear whether these stars will act like supernovadirectly collapses into black holeor evolve from the red supergiant stage to the yellow supergiant stage before ending its life. “WOH G64 may be the solution to this problem.”
The team’s findings are the first to demonstrate that an extreme stellar object can change its temperature and evolve from red to yellow over the course of a year, and in a smooth, quiet way.
“This is particularly surprising because rapid changes in stars are often associated with violent or sudden processes,” Muñoz-Sanchez continued.
However, that’s not all the team has discovered about the massive star. The scientists also discovered that WOH G64 is not alone.
Live fast, die young… but you’re not alone
At only 5 million years old, WOH G64 is a young star in the universe, so it is facing the end of its life, which seems a bit unfair in the universe compared to other stars, such as the middle-aged Sun, which is 4.6 billion years old. This occurs because massive stars like these “live fast and die young,” depleting the supply of fuel needed for nuclear fusion faster than stars of modest size.
While all massive stars are so short-lived, the final stages of the lives of these stars, Titans, are less certain. For example, not all red supergiants shed their outer layers as their cores shrink to become yellow supergiants.
“Yellow supergiants are extremely rare because they represent a brief transitional phase between the red supergiant phase and the final supernova explosion,” Muñoz-Sanchez said. “Therefore, the number of yellow supergiants currently known is very small, only a few dozen in total.”
In order for this yellow supergiant transition to occur, a massive star needs a stellar wind powerful enough to strip away its outer shell of previously shed stellar material, a process that increases its temperature. However, only the brightest red supergiants can drive material outflows powerful enough to trigger this transition phase, ultimately leading to the star’s death.
Artist’s impression of WOH G64’s two faces: a red supergiant discovered in 2013, and a yellow supergiant binary discovered in 2014 with a hot star. Photo credit: Patryk Iwanek/OGLE
The team also discovered that the massive star is actually part of a binary system, existing with a companion star. If the primary star greedily drags material away from its companion, then the potential reasons for its transformation are complicated.
“Binary interactions may also play a crucial role in the formation of yellow supergiants,” Muñoz-Sanchez said. “If mass transfer or envelope stripping occurs in a binary system, the red supergiant’s envelope may be partially removed, potentially driving its evolution toward yellow temperatures.”
The researchers went on to explain that in a binary-driven scenario, the star’s evolution is caused by interactions with its companion star, binary system would be embedded in a common shell, the cocoon of gas surrounding the two stars, making it possible Appear As a red supergiant star. Partial ejection of this envelope will then reveal two stars.
“Alternatively, even if the system is a binary, the transition could be driven by internal processes within the star. In this case, the star may have experienced an extraordinary eruptive event lasting more than 30 years and is now returning to a yellow quiescent state,” Muñoz-Sanchez added. “Both of these possibilities are extremely rare, and witnessing either of them occurring on human timescales is almost unprecedented.”
Therefore, the team does not yet know whether its evolution is the result of interactions between WOH G64 and its binary companion, or whether the metamorphosis is intrinsic to the star itself.
“Recent observations suggest that some other extreme red supergiants may also be located in binary systems,” explains Muñoz-Sanchez. “Understanding whether the extreme properties of these stars result from their intrinsic nature or from binary interactions is critical for studying populations of evolving massive stars, predicting their deaths, and explaining the supernovae they produce, a phenomenon that is not yet fully understood.”
Understanding the dualistic nature of WOH G64 is not only the key to understanding its life; These details are also integral to his death.
The ongoing exchange of mass between stars can lead to their collision and the merger of the two components. However, if interactions between stars are slight or non-existent, the host star can evolve into core collapse, ultimately leading to a supernova explosion or direct collapse into a black hole. “From an astronomical perspective, WOH G64 appears to be a highly evolved system that has the potential to undergo core collapse ‘soon’. In this case, ‘soon’ corresponds to a time scale ranging from a hundred to a few thousand years,” Muñoz-Sanchez said. “Such an event would be extraordinary and the likelihood of it happening in our lifetime remains small.
Of course, we’re not even sure if the star will explode as a supernova. “
A paper on these results was published in the journal on Monday (February 23) nature.