Stars can do many things. They can heat up, expand, explode, and even collapse into a black hole. They cannot, as a general rule, simply disappear. However, that is what seems to have happened to an ultra bright star in the constellation Aquarius. Astronomers searched for this well-known star in late 2019 only to discover that it was missing. The team has come up with several possible explanations, but this is a real head scratch.
Astronomers studied this object in great detail between 2001 and 2011 because it is not an ordinary star. It is (or was it?) A very rare type of ancient star called a massive luminous blue variable (LBV). And “bright” is putting it on smoothly. The light output varied (as the name implies), but on average it was approximately 2.5 million times brighter than the sun. That’s the only reason we could see it: It resides in the Kinman dwarf galaxy about 75 million light-years away.
Last year, the team at Trinity College Dublin expected to use the Very Large Telescope of the European Southern Observatory to control this object, but it was no longer visible. Was he dead? This star was advancing towards the end of its life cycle, which is why it was so interesting in the first place. However, a dying star supernova would leave evidence, and there were no signs of such an event.
The researchers have returned to look at the oldest LBV records to find some possible explanations. Based on these previous data, the team speculates that the star may have experienced a strong period of explosion the last time astronomers looked in its direction. That may have ended around 2011, causing the star to darken enough that we can no longer distinguish it from the background so far. That suggests that the LBV could explode again at any time and become visible.
A more exciting and speculative hypothesis is that the LBV did indeed buy the farm, but in a way that we have never seen before. It may have been somehow burned and collapsed into a black hole without all the usual telltale signs. If this is true, there should be a black hole with around 100 solar masses lurking in the Kinman dwarf galaxy. This has the potential to rewrite our understanding of the solar life cycle.
For now, we are caught up in speculation. The team hopes to use ESO’s upcoming Extremely Large Telescope (ELT) to take a closer look and solve this mystery once and for all. That project is slated to begin in 2025.
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