The VASCO team ("Vanishing & Appearing Sources during a Century of Observations") is investigating 150,000 candidate objects that have appeared or disappeared from the sky since the 1950s.
A project lead by an international team of researchers use publicly available data with images of the sky dating as far back as the 1950s to try to detect and analyse objects that have disappeared over time. In the project "Vanishing & Appearing Sources during a Century of Observations" (VASCO), they have particularly looked for objects that may have existed in old military sky catalogues from the 1950s, not to be found again in modern sky surveys. Among the physical indicators that they are looking for are stars that have vanished in the Milky Way."Finding an actually vanishing star--or a star that appears out of nowhere-- would be a precious discovery and certainly would include new astrophysics beyond the one we know of today," says project leader Beatriz Villarroel, Stockholm University and Instituto de Astrofísica de Canarias, Spain.
When a star dies it either undergoes very slow changes and becomes a white dwarf or it dies with a sudden bright explosion i.e. supernova. A vanishing star can be an example of an "impossible phenomenon" that could be attributed either to new astrophysical phenomena or to extra-terrestrial activity. Indeed, the only non-ETI (extra-terrestrial intelligence) explanation for a vanishing star would be exceedingly rare events called "failed supernovae." A failed supernovae is theoretically predicted to occur when a very massive star collapses into a black hole without any visible explosion. Other physical indicators of ETI activity that the authors are looking for are signs of red interstellar communication lasers and Dyson spheres. A Dyson sphere is a hypothetical giant structure surrounding a star to harness its energy.
To be honest, it would be a lot more interesting if there were only a handful of examples -- 150,000 disappearing objects makes me think that it isn't aliens.
