However, an intriguing possiblity is that if Dyson spheres were built around common dwarf stars and they break after a while, we might find pieces of broken Dyson spheres in interstellar space.

In a recent paper, I suggested that the anomalous interstellar object, `Oumuamua, discovered in 2017, might have been a piece of a broken Dyson sphere because of its unusual flat shape and non-gravitational acceleration. If Dyson spheres exist around common stars, this might not be unreasonable.

Once a civilization abandons its Dyson sphere, the shell’s infrastructure will be punctured by micrometeorites and lose its functionality within millions of years.

…

If other civilizations constructed Dyson spheres, which disintegrated over time, their fragments could have given rise to the unusual shape and light sail characteristics of the interstellar object `Oumuamua.

Starting in 2025, we will be able to search for pieces of broken Dyson spheres with the Vera C. Rubin Observatory in Chile by employing its 3.2-billion-pixel camera to survey the southern sky every 4 days. In view of this new observatory, “the sky’s the limit,” as the popular saying goes.