One hundred red objects in deep space seem to have mysteriously vanished over the past 70 years.

Researchers say the objects could be lasers that aliens use to communicate across interstellar space, or stars that aliens covered with megastructures.

The objects could also be the first evidence of "failed supernovae": stars that collapsed directly into black holes, without any supernova explosion.

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One hundred mysterious red objects in the sky have vanished inexplicably over the past 70 years. One possible explanation for their disappearance: alien technology.

The discovery of these disappearing objects came out of a project called "Vanishing and Appearing Sources during a Century of Observations," or VASCO, which analyzes images of the sky from public records as far back as the 1950s. The project aims to locate objects in space that have appeared or disappeared by comparing older photos with recent ones.

In doing so, an international team of scientists identified about 100 objects that vanished in short periods, some of which rapidly became several thousand times as bright before they disappeared.

The astronomers, who published these results in The Astronomical Journal last week, said the mysterious objects could be a sign of alien activity. Another explanation they suggested is that the objects are stars that have undergone a never-before-seen process of collapsing into a black hole without the characteristic explosion of a supernova.

"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," Beatriz Villarroel, the project leader, said in a press release.

If not alien technology, this could be the first evidence of a failed supernova

An object visible in an old plate (left, in the center of the square) has disappeared in a later plate (right). Villarroel et al. (2019)

VASCO researchers' old images of the sky often come from military records. From their comparison work, they have identified 150,000 candidate objects that might have disappeared. They've examined 15% of those so far, leading them to pinpoint 100 objects that did indeed seem to vanish.

If the missing objects have nothing to do with aliens, the scientists think they may have discovered the first evidence of a "failed supernova."

The largest star in the Eta Carinae system in ultraviolet and visible light as it nears the end of its life and a probable supernova explosion. After a supernova, material expelled in the explosion can form a nebula. NASA Goddard

Usually, a supernova explosion occurs after a massive star (those with at least eight times the mass of our sun) runs out of hydrogen fuel. At that point, heavier elements in its core start to fuse. Eventually, the star's core runs through the entire periodic table, burning every possible element until it reaches iron. Fusing iron takes more energy than it produces, so the star can't build up enough internal pressure to maintain its shape and size.

Once the star loses the outward-pushing pressure from its core, it succumbs to its own gravity. Its outer layers collapse and explode, spewing heavy metals into space. The star's remaining core collapses into a black hole or neutron star.

Theoretically, in the event of a failed supernova, a dying star would skip the explosion and collapse almost immediately into a black hole. That could explain the vanishing red objects.

Or here's where aliens might come in: Rather than stars, some of these disappearing red objects — those that appear only once in one image — could be lasers that aliens use to communicate across interstellar space, the researchers said.

Alternatively, the objects could be stars that disappeared because an alien civilization built large structures around them, called Dyson spheres, to harness the stars' energy.

"None of these events have shown any direct signs" of being extraterrestrial intelligence, Martin López Corredoira, an author of the study, said in the release. "We believe that they are natural, if somewhat extreme, astrophysical sources."

Still, the VASCO researchers say the 100 disappearing objects should be investigated further. In the meantime, they plan to sift through photos of about 125,000 more space objects that may have met a similar fate. They also intend to open the project up to citizen scientists and use artificial intelligence to identify more mysterious vanishing objects.