# Natural and Artificial Spectral Edges in Exoplanets

## TL;DR

This paper discusses how spectral features like the natural 'red edge' of vegetation and artificial edges from photovoltaic arrays on exoplanets could be detected through future observations, indicating biological or technological activity.

## Contribution

It introduces the concept of artificial spectral edges as detectable markers of technological civilizations on exoplanets, expanding the scope of astrobiological signatures.

## Key findings

- Spectral edges can be detected photometrically in reflected light.
- Artificial edges are shifted shortwards of natural vegetation edges.
- Detection could indicate presence of photovoltaic arrays or vegetation.

## Abstract

Technological civilizations may rely upon large-scale photovoltaic arrays to harness energy from their host star. Photovoltaic materials, such as silicon, possess distinctive spectral features, including an "artificial edge" that is characteristically shifted in wavelength shortwards of the "red edge" of vegetation. Future observations of reflected light from exoplanets would be able to detect both natural and artificial edges photometrically, if a significant fraction of the planet's surface is covered by vegetation or photovoltaic arrays respectively. The stellar energy thus tapped can be utilized for terraforming activities by transferring heat and light from the day side to the night side on tidally locked exoplanets, thereby producing detectable artifacts.