SETI & Technosignatures

Specular Reflections From Artificial Surfaces As Technosignature

By Keith Cowing
Status Report
June 23, 2023
Filed under , , , , , ,
Specular Reflections From Artificial Surfaces As Technosignature
The geometry of specular reflection from the structures present on the surface of the planet. The artificial structures are drawn on the surface (marked as A1, A2, and A3). The star has a finite size as seen from the planet; hencethe incident rays will have a variation in incident angles. The reflected rays, however, are parallel in the direction of theobserver as the distance of the planet from the observer is very large. Only those rays that are reflected in the direction of theobserver are shown here. — astro-ph.EP

Direct imaging of exoplanets will allow us to directly observe the planet in reflected light. Such a scenario may eventually allow for the possibility to scan the planetary surface for the presence of artificial structures made by alien civilizations. Detectability of planetary scale structures, called megastructures, has been previously explored.

In this work, we show that it is possible to detect structures of much smaller scale on exoplanetary surfaces by searching for the specular reflection of host starlight from the corresponding structures. As the planet rotates, these reflections can manifest as an optical transient riding atop the rotational light curve of the planet.

Due to the directional nature of specular reflection, the reflected signal is very strong, and it is comparable to the planetary flux for surfaces covering only few ppm (parts per million) of the total planet surface area. By tracking the planet around its orbit, it should be possible to scan the planetary surface for any such structures covering a size larger than a few ppm of planetary surface.

The proposed method will aid in the search for extra-terrestrial intelligence in the era of direct imaging of exoplanets.

Bhavesh Jaiswal

Comments: 2 figures, 4 pages, published in Astrobiology
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Popular Physics (physics.pop-ph)
Cite as: arXiv:2306.07859 [astro-ph.EP] (or arXiv:2306.07859v1 [astro-ph.EP] for this version)
Submission history
From: Bhavesh Jaiswal
[v1] Tue, 13 Jun 2023 15:43:43 UTC (268 KB)

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