Earlier this year, we published an account of three stars that vanished from the night sky forever within an hour in July 1952, leaving behind a conundrum with multiple possible explanations. However, by no means have these stars been the only ones to vanish unearthly. The Vanishing and Appearing Sources during a Century of Observations (VASCO) project identified approximately one hundred stars that had vanished from view over the previous seven decades without a definitive explanation in 2019.
Comparing images acquired by the US Naval Observatory beginning in 1949 with those obtained from the Pan-STARRS sky survey between 2010 and 2014, the VASCO project did so. The team’s software identified approximately 150,000 potential sources of light that had vanished during the intervening years.
It was subsequently cross-referenced with additional datasets to refine its scope. They were subsequently left with 24,000 candidates, which they reviewed by hand to rule out camera malfunctions and other errors. At the end of it, they had around 100 plausible candidates for real sources of light that disappeared from our view.
Stars may dim like Betelgeuse or erupt as a supernova leaving an afterglow for hours or days, but generally do not simply vanish from view. One plausible explanation is that they failed to go supernova, instead collapsing into a black hole. This is thought to be exceedingly rare at less than 1 in 90 million, however, and would likely not explain why so many points of light have gone missing. A later study by VASCO, looking at further vanishing candidates, placed the failed supernova detection rate at less than 1 in 600 million.
Other possibilities could be gravitational lensing, where space-time is warped by immensely massive objects, sometimes magnifying objects far into the distance, or other brief bursts of light such as gamma-ray bursts getting captured in older surveys. Closer-moving objects, such as asteroids, could also account for these disappearances.
While studying these objects is of interest to astrophysics who may have to explain mechanisms for star disappearance, one of the motivating factors behind the search was a lot more out there: the search for a Dyson Sphere, a hypothetical way advanced civilizations could harness the power of a star by surrounding it with solar panels. Searching these transients could (and that’s a fairly big could) lead us to an advanced civilization.
“If a region of the sky tends to produce an unexpectedly large fraction of candidates relative to the background, this region or ‘hot spot’ may deserve some extra attention.” a distinct team wrote in their 2019 paper in The Astronomical Journal.
However, the follow-up study did not identify viable candidates for Dyson Spheres either, leaving us with a whole lot of missing stars and not much by way of explanation.