Now you don't. A study that examines old photographic plates of astronomical observations and compares them with more recent ones has found about one hundred objects that no longer appear in visible light. With bonus "extraterrestrial aliens!!" clickbait material included.
"Short-lived light sources discovered in the sky" |
Phys.Org (https://phys.org/news/2019-12-short-lived-sources-sky.html)
Quote(https://i.imgur.com/rubdr2t.jpg)
A source visible in an old plate (left, seen as the bright source at the centre of the square)
has disappeared in a later plate (right).
Image credit: Villarroel et al. (2019)
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.
"As a by-product, VASCO has the potential to discover rare extremely-variable objects. These can shed light on fast hard-to-observe phases of stellar evolution and active galactic nucleus," says co-author Sébastien Comerón, Oulu University, Finland.
[Continues . . . (https://phys.org/news/2019-12-short-lived-sources-sky.html)]
Interesting! Never heard of that kind of highly variable stars.
Tchaikovsky would argue that the images seen, at this time of year, are actually Sugarplum fairies.
Stellar peek-a-boo.