If an extraterrestrial ship left its waste near the Earth, here is what it could look like | Science

Iridium lightings are a familiar sight for sky observers: bright lightning occurs when sunlight bounces off the solar panels of the 66 low-orbit satellites of the iridium communication system. Now, a researcher involved in researching an extraterrestrial intelligence wonders what could mean even more distant flashes – perhaps an artifact or a bright extraterrestrial spacecraft?

To find out, he calculated what a brilliant "technosignature" might look like. He began by observing that even though a reflective surface is visible from far away, our ability to see it from the Earth depends on the surface, the direction in which it is oriented, its rotation or the sensitivity of the Earth. . linked telescopes. The pan-survey telescope and rapid reaction system (Pan-STARRS1), a 1.8-meter telescope located in Haleakala, Hawaii, sweeping the sky in search of potentially dangerous objects close to the Earth, could for example spotting a mirror the size of an astronomical unit, the distance between the sun and the Earth, if it rotated slowly. For Pan-STARRS1 to see a fast rotating mirror at the same distance, it must be the size of a tennis court.

Given these variables, the researcher estimates that it would require millions of mirrors through the internal solar system to see one in a single Pan-STARRS1 exhibit, he says today on the preprint server arXiv. These chances could increase by focusing on Lagrange points, gravitational chasms where extraterrestrial detritus could accumulate. If only a few hundred mirrors were present, a much smaller telescope could spot one. But the fact that we have not yet seen such flashes suggests that all extraterrestrial visitors – if they are there – are doing a good job of cleaning up after themselves.