This spectacular star was 2.5 times brighter than our Sun and has disappeared before telescopes . It was about 75 million light-years away in the Kinman dwarf galaxy; it was a very special star, a “luminous blue variable” with an estimated mass tens of times greater than that of our star.
Astronomers observed it from 2001 to 2011 as it was experiencing an outburst, was in the last stages of its lifespan, and was glowing brightly, but recent observations, or rather the lack of them, are the reason the star he is the protagonist: he is not visible. It seems to have disappeared, something that is quite unusual.
Luminous blue variables are massive evolved stars that can change their luminosity tremendously, show dramatic changes in their brightness and spectra, and leave a distinctive mark on the galaxies that host them, making them easily detectable. Of course, if they are on the verge of death, they generally go supernova. But there are no traces of the supernova or the star. What happened then?
“We were surprised to find that the star was gone!” Says Andrew Allan, an astrophysicist at Trinity College in Dublin, Ireland, and lead author of the new study published in the Monthly Notices of the Royal Astronomical Society.
Data from the Hubble telescope and other files indicated that the star may have been experiencing a strong explosion period that likely ended sometime after 2011.
Based on their observations and models, the researchers suggest two explanations for the disappearance of the star and the lack of a supernova, related to this possible outbreak.
A rather exciting possibility is that the star has collapsed into a black hole, without a supernova, something that is considered a necessary step for such an event to occur.
“If true, this would be the first direct detection of a monster star that ends its life in this way, ” says Allan.
The black hole scenario would be quite unlikely, but it is not unknown. There is a process known as a “failed supernova” that would explain this event and a possibility has been considered as to why different types of stars have been found to be missing, including two red supergiant stars in other galaxies. In a failed supernova, the star lights up as it would in the early stages of the supernova, but then it does not rise as much as a supernova would. Although the result is similar , the process that originates it is not at all clear.
The other possibility is that “the outburst may have resulted in the luminous blue variable transforming into a less luminous star, which could also be partially obscured by dust,” the researchers explain.
Unfortunately for us, it is difficult to find out exactly what has happened . Because the star is – or was – in a dwarf galaxy called PHL 293B, 75 million light years away, it is too far away for us to distinguish individual stars with our current instruments.
Referencia: “The possible disappearance of a massive star in the low metallicity galaxy PHL 293B” Monthly Notices of the Royal Astronomical Society (2020). academic.oup.com/mnras/article … .1093/mnras/staa1629
