How could it get lost? It was a giant star. 2.5 million times brighter than the sun. It was in the Kinman dwarf galaxy 75 million light years away. His absence was determined by the Very Large Telescope (VLT) of the European Southern Observatory. The star that disappeared into space could reveal a new star death. It could fall into a black hole without first producing a supernova.
Far far away
Kinman is in the constellation Aquarius. Too far for astronomers to see their individual stars, but they can see the signatures of some. From 2001 to 2011, the light from the galaxy consistently indicated that it contained a variable blue light star. Stars of this kind are the brightest known. They leave specific footprints that scientists can identify.
It was at a late stage in its development. It was very interesting to learn more about how stars die. When the researchers pointed the VLT at the distant galaxy in 2019, they could no longer find the telltale signatures of the star. Where was the star that disappeared from space? “It was gone,” says Andrew Allan of Trinity College in Dublin, Ireland. He is responsible for the study that appears in the “Monthly Notices of the Royal Astronomical Society”.
Now it is, now it is not
What happened to him? “It is possible that one of the most massive stars in the local universe gently enters the eternal night.” This is stated by team member Jose Groh, also from Trinity College.
The team relied on older data between 2002 and 2009. The comparison with the new observations was revealing. Old data suggest that the star in Kinman may have experienced a strong explosion period. It probably ended sometime after 2011. Blue light variables like this tend to experience huge explosions throughout their lives. Its mass loss rate skyrockets and its luminosity increases dramatically.
In the black hole
Astronomers have proposed two explanations for the star’s disappearance and the lack of a supernova. The outbreak could have resulted in our protagonist turning into a less shining star. It could also be partially hidden by dust. Alternatively, the team says the star may have fallen into a black hole. But without triggering a supernova explosion. This would be a rare occurrence: Our current understanding of how massive stars die suggests that most of them end their lives in a supernova. It would be the first direct discovery of a monstrous star that ends his life in this way.
The authors acknowledge that further studies are needed to confirm the fate of this star. ESO’s powerful Extreme Large Telescope (ELT), planned for 2025, may be able to solve this cosmic mystery.