Kinman’s dwarf galaxy (PHL 293B) is located about 75 million light-years from the Milky Way in the constellation Aquarius. This is too far for Earth observatories to consider its individual stars. At the same time, while studying the galactic spectrum, astronomers found a kind of “signature” left by a blue variable star of high luminosity, whose brightness is about 2.5 million times higher than the solar one.
Stars of this type are very unstable. They show sharp irregular changes in their spectra and brilliance. But even with luminosity jumps, such luminaries have certain observational signs. In the period from 2001 to 2011, astronomers recorded them in the spectrum of the Kinman galaxy. Available data indicated that the blue variable star reached the late stage of its evolution, after which it should wait for a collapse with the transformation into a neutron star or a black hole.
In 2019, an international team of scientists sent all four of the main “units” of the Very Large Telescope (VLT ESO) to the Kinman galaxy in the hope of exploring the sun. But to the researchers’ surprise, they were unable to find any signs indicating the presence of a blue variable star. A few months later, the group used the X-shooter receiver mounted on the same telescope. And again, they failed to find a star.
To uncover the mystery of the disappearance of the luminary, astronomers turned to the archive of data from VLT and other observatories. Analysis showed that the star in the dwarf Kinman galaxy could be in the phase of a strong flare, possibly ending in the 2011 region. Similar events are part of the evolutionary process of blue variables. During flares, the rate of loss of their mass reaches a peak, and the luminosity increases sharply.
Based on observational data and the results and simulations, astronomers have proposed two potential explanations for the disappearance of a star. The first is that the flash could be caused by the transformation of a blue variable of high luminosity into a luminary with a lower luminosity. In addition, the star could be partially hidden by dust clouds, which contributed to a sharp drop in brightness and made it invisible to VLT.
Another possibility is to collapse a star into a black hole without the formation of a supernova. It is worth noting that, according to modern ideas, such events are extremely rare. It is believed that the vast majority of massive stars end their lives with a supernova flash.
Astronomers hope that additional observations will help establish the true fate of this luminary. They have especially great hope in the Extremely Large Telescope (ESO ELT), which will begin observations in the second half of this decade. Its resolution should be enough to make out individual stars in distant galaxies like the Kinman galaxy.