Flashes of giant cities on alien worlds could be visible from Earth

As current technology already allows direct imaging of exoplanets, this opens up new opportunities to search for intelligent life in the Universe.

New research suggests that we could see alien cities from Earth, equivalent to a fraction of the size of large terrestrial urban areas like New York or Tokyo, using a characteristic of light known as specular reflection. However, although the technology is already available, the possible observation, in case those cities really exist in other worlds, depends on a set of factors and circumstances that are not so easy to match.

The researcher Bhavesh Jaiswal, from the Indian Institute of Sciences, proposes in a new study recently published in ArXiv that we could appreciate alien cities from Earth and verify technological signatures of intelligent extraterrestrial life in one of the more than 5,000 exoplanets discovered to date, using a technique known as specular reflection.

As Jaiswal explains in his scientific article, direct images of exoplanets will allow us to observe these distant worlds in detail in reflected light. This scenario could eventually make it possible to “scan” the planetary surface in search of artificial structures made by extraterrestrial civilizations.

Although the possible identification of structures on a planetary scale, called megastructures, has been previously explored in different studies and investigations aimed at the search for technological signatures of advanced civilizations, until now these efforts have been concentrated almost entirely in areas of enormous dimensions. , in the style of the ecumenopolis of the fictional planet Coruscant from the “Star Wars” saga, a gigantic city that encompassed the entirety of a planet. However, Jaiswal believes that it is possible to detect much smaller-scale features on exoplanetary surfaces by looking for the specular reflection of light from the host star off the features. What does this technique consist of? According to an article published in Universe Today, the specular reflection phenomenon occurs when light reflects directly back at an observer, rather than diffuse light shining in all directions.

An example is the strong, sometimes blinding flash of an ocean wave, or the intense shine of the metallic bodywork of a sports car in sunlight. In both cases, the light is concentrated so much in a specific point that it allows you to “amplify” that aspect among all the wide surrounding scenery.

Future efforts to directly image planets in reflected light are in full swing for both space telescopes and extremely large ground-based telescopes, although the technology to take advantage of specular reflection is already available. However, it is not so simple to obtain images of this type of an exoplanet, and even less to detect in them a medium-sized city, which could correspond to a fraction or sector of the large cities on Earth. To achieve this, light from the exoplanet’s host star would have to bounce off the planetary body in exactly the right place and at the right angle, to reach an observer here on Earth. In addition, the dynamics of specular reflection imposes a limit on the size of an area that can reflect light towards an observer, therefore it would have to be possible to specifically observe the sector of the exoplanet in which a relatively small city is located, or a part of a larger city. In any case, before being able to observe these alien cities, it is essential that they actually exist, something that has not yet been proven. Beyond this, Jaiswal’s proposed method could help in the search for extraterrestrial intelligence in the era of direct exoplanet imaging, which is just around the corner based on the latest advances in astronomical observing technologies. .

source: https://arxiv.org/abs/2306.07859