Astronomers are observing an unusual transformation in one of the largest known stars in the universe, WOH G64, which may offer clues about the lives and deaths of these massive celestial bodies. Understanding stellar evolution is crucial for comprehending the origins of elements essential for life.
Located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way approximately 163,000 light-years from Earth, WOH G64 has been under observation for more than three decades.
In 2014, researchers noted a significant change in the star’s color, indicating a rapid shift from a red supergiant to a yellow hypergiant. This transition, characterized by a dramatic increase in surface temperature, occurred quickly on a cosmic timescale and without any evidence of an eruption or explosion.
“Typically, the evolution of a star takes place on timescales of billions of years. On human timescales, we only observe more abrupt and violent events, such as eruptions, the merger of two stars or their explosive deaths,” said astronomer Gonzalo Muñoz-Sanchez, lead author of the research published this week in the journal Nature Astronomy.
WOH G64 has a mass approximately 28 times that of our sun, and its diameter could be around 1,500 times larger. If positioned in our solar system, its surface would extend beyond the orbit of Jupiter and Saturn.
At roughly 10 million years old, WOH G64 appears to be nearing the end of its life. For comparison, our sun is about 4.5 billion years old and is expected to continue burning for another 5 billion years. The star is located approximately 160,000 light-years from Earth.
“WOH G64 is a massive star and very different from our sun,” Muñoz-Sanchez explained.
Stars with masses between eight and 23 times that of the sun are expected to evolve into red supergiants and eventually explode as supernovae.
The fate of stars with masses between 23 and 30 times that of the sun remains less certain. It is still unclear whether they explode as supernovae, collapse directly into black holes, or evolve from a red supergiant phase to a yellow hypergiant phase before ending their lives.
Black holes are incredibly dense objects with such strong gravity that not even light can escape.
Adding to the complexity of understanding WOH G64 is the fact that observations indicate the star is gravitationally bound to another star in what is called a binary system. Researchers have not determined the size or characteristics of the companion star, but say the two may eventually merge.
