7 potential 'alien megastructures' spotted in our galaxy are not what they seem

A team of astronomers combed through a collection of odd stars that are candidates for Dyson spheres — artificial constructs designed by aliens to leech energy from stars. Instead, the scientists found, the weird stars are more likely to be "hot DOGs" — hot dust-obscured galaxies.

In early 2024, astronomers combed through more than 5 million stars from the Wide-field Infrared Survey Explorer, Gaia and 2MASS sky surveys, searching for stars that seemed to have excess infrared radiation. According to the researchers, this extra infrared signal could be interpreted as the signature of a Dyson sphere. 

First proposed in the 1960s by physicist Freeman Dyson, these hypothetical constructs would essentially be enormous shells that wrap around stars, absorbing as much light energy as possible. In Dyson's theory, the material used to construct these spheres would come from disassembled planets in that star's system.

Alien civilizations could use Dyson spheres to acquire millions of times more solar energy than we have access to on Earth while also giving themselves a spiffy new structure to live on. But no energy collection or usage system is perfect. So, while the Dyson sphere collects radiation from the star on its inside, it also emits heat from its outside.

To us, that would make a Dyson sphere appear as a star with a lot more infrared radiation than normal. In the latest search, the astronomers identified seven stars within 1,000 light-years of Earth that emit an abnormally large amount of infrared radiation, making them Dyson sphere candidates.

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But in a more recent study published to the preprint server arXiv in May, a new team of astronomers examined those seven candidates in greater detail. They found that three are very close to a peculiar kind of galaxy known as a hot dust-obscured galaxy, or "Hot DOG."