Reflected light from exoplanets will help astronomers locate cities or megastructures elsewhere in the universe. This discovery gives scientists the opportunity to search for intelligent life on a scale that previously seemed impossible.
Previously, scientists believed that in order to detect technosignals and signs of alien life, large megastructures that surpass our earthly ones are needed. However, recent research by Bhavesh Jaiswal of the Indian Institute of Science shows that we can see much smaller cities and structures thanks to the specular reflection of light.
Reflected-light imaging of exoplanets has become a reality thanks to advances in spectroscopy and techniques for blocking starlight. Spectroscopy allows you to study the composition of the planet’s atmosphere, while blocking the light of a star helps to observe the planet itself.
However, how can you see something as small as a city? In this matter, the mirror reflection of light will help. This phenomenon occurs when light is reflected directly at the observer, rather than being scattered in all directions. Like the gleam of an ocean wave or the gleam of a metal car surface in the sun, specular reflection makes it possible to spot cities or megastructures on exoplanets.
Scientists are actively working on developing methods for direct imaging of planets in reflected light using space and ground-based telescopes. This method will be applicable to both red dwarfs and sun-like stars.
However, the visibility of the specular reflection depends on various factors such as the size and materials of the city or structure. For example, on a planet the size of Earth, an appreciable specular reflection can cause an area of only about 5.4 parts per million of the entire planet. This corresponds to about 2800 square kilometers or a small earthly city.
However, in order to detect a mirror image, we need luck and certain conditions. A planet with a slow rotation or a structure with a width in the longitudinal direction will increase the chances of detection. In addition, the planet’s axis must be aligned so that the city is at the correct latitude to reflect the light towards the observer.
Although the possibility of discovering a city on an exoplanet is still small, the technology for such a discovery is already available. Astronomers continue to research and develop methods for imaging planets and structures in reflected light.