So yet, no proof of sentient aliens has been discovered elsewhere in the universe. However, if they do exist, they might be found on Dyson spheres around the husks of sunlike stars known as white dwarfs dispersed across the Milky Way, according to a recent article.
In an email to Live Science, study co-author Ben Zuckerman, an emeritus professor of physics and astronomy at the University of California Los Angeles, said that's where we should be focused our hunt for extraterrestrials.
Astronomers could estimate how many sophisticated civilizations exist in the galaxy based on the results of that search, he added.
Long live the civilization
Energy is required by any civilized society for food, transportation, combat, comfort, and convenience. According to The World Counts, Earth's 7.8 billion people consume roughly 580 million million joules of energy every year, which is comparable to the energy production of almost 14,000 million tons of oil (opens in new tab). Indeed, practically all human energy is derived from fossil fuels, as we lack the technological know-how to rely on the solar system's greatest energy generator: the sun.
Solar panels covering every square inch of the Earth's surface would create more than 1017 joules of energy every second. Even so, the majority of the sun's energy, around 1026 joules per second, would be lost.
Dyson spheres, named after legendary physicist Freeman Dyson, who conceived the concept in 1960, were created with this goal in mind. If a sophisticated civilisation truly wishes to tap into its parent star's massive energetic output, they must construct megastructures to collect it, blocking off at least portion of the star's light and transforming it into something useful. Owing to tremendous tidal and rotational strains, Dyson's initial plan of a solid sphere (with 100 percent solar coverage) is unworkable due to stability concerns. It would be impossible to hold the star at the center, and the entire sphere would disintegrate. Even yet, it's possible to envisage a technologically advanced society erecting rings or swarms of massive solar-panel-covered buildings to complete the task.
Failed start-ups
However, no matter how evolved a race is or how many Dyson sphere-like structures they construct, they will have to deal with the fact that all stars have a finite lifespan. If a civilisation evolved around a regular sunlike star, that star will eventually transform into a red giant, leaving a cold white dwarf behind. The inner planets of its solar system will be roasted as a result of this process, while the outer planets will be frozen when the white dwarf cools.
As a result, sticking stationary on a planet's surface is not a feasible long-term choice. That implies any aliens could either pack up and depart, looking for a new home system, or construct a chain of dwellings that harvest the surviving white dwarf's radiation.
According to a recent study authored by Zuckerman and published in the journal(opens in new tab) Monthly Notices of the Royal Astronomical Society in May, it appears implausible that an extraterrestrial culture would choose to travel to a new star simply to create a Dyson sphere. As a result, they will only construct megastructures around their home stars, which will eventually become white dwarfs.
Scientists can now draw a clear link between star lifespan and the presence of Dyson spheres. So, scientists looking for Dyson spheres around white dwarfs and finding none, according to Zuckerman, can help estimate how many sophisticated civilizations may exist in the galaxy. The rationale goes like this: Only a small percentage of the galaxy's white dwarfs have been measured by astronomers. We should see at least one Dyson sphere in our surveys if enough aliens opt to create Dyson spheres around their white dwarf habitats. If we don't observe any, then the number of extraterrestrial civilizations erecting Dyson spheres around white dwarfs will be limited. Of course, there could be aliens who don't build Dyson spheres, or aliens who build spheres around different kinds of stars, but Zuckerman claims that over the Milky Way's history, the most likely outcome for advanced civilizations is to build a Dyson sphere around their white dwarf, and that we should concentrate our searches in that direction.
Taking the long view
Surprisingly, scientists have previously discovered several white dwarfs with excessive infrared emission, but according to the research report, this is attributable to dust in such systems, not megastructures.
There has been no evidence of Dyson spheres in previous examinations of white dwarfs. Given the expected number of white dwarfs in the Milky Way, Zuckerman calculates that only about 3% of habitable planets surrounding sun-like stars give rise to a civilization that builds a Dyson sphere around the ensuing white dwarf. However, because there are so many planets around sun-like stars, the researchers determined that this computation only yields a maximum of 9 million probable white dwarf sphere-building civilizations in the Milky Way.
But, in the end, no one knows how many intelligent civilizations exist in the Milky Way, if any at all, according to Zuckerman.
"Some astronomers, like myself, believe that technological life might be quite uncommon," Zuckerman added. "Indeed, we may have the most sophisticated technology in our galaxy's history. But because no one knows, it's worth looking for proof."
