In a groundbreaking new article, Professor Irina Mullins comes up with an intriguing idea: Aliens may not travel on starships but on lonely planets through interstellar space.

In the International Journal of Astrobiology, Professor Mullins states that “I propose that extraterrestrial civilizations may use free-floating planets as interstellar transportation to reach, explore and colonize planetary systems.”

That may seem a bit far-fetched, but there’s a fascinating line of thought behind it that also has very interesting implications. For example, for our search for extraterrestrial life.

“I propose possible techno signatures and artifacts that may be produced by extraterrestrial civilizations using free-floating planets for interstellar migration and interstellar colonization, as well as strategies for the search for their techno signatures and artifacts,” says Mullins.

The problem with searching for life in outer space is that we don’t know what we’re looking for—or where to look. The idea of aliens traveling across interstellar space isn’t actually so crazy when you think about it: If they’re intelligent enough to travel this far, they could certainly travel farther if they were able to harness the power of gravity and black holes.

And why wouldn’t they? It would be like us sending an astronaut into orbit around our own planet instead of just walking into another country on foot!

Traveling

For example, aliens may leave their home planets out of curiosity or due to necessity. A dying star, for instance, might force aliens to flee in search of a new home. However, interstellar exploration is extremely challenging because the distances involved are so large.

“Extraterrestrial civilizations would most likely face serious or insurmountable technical problems when using spacecraft for interstellar migration of large populations. Therefore, they may use other methods of interstellar travel. Some extraterrestrial civilizations may build stellar engines,” says Mullins.

• Shkadov, Reference Shkadov1987
• Shkadov et al., Reference Shkadov, Illarionov and Sonin1989;
• Korycansky et al., Reference Korycansky, Laughlin and Adams2001;
• McInnes, Reference McInnes2002;
• Forgan, Reference Forgan2018

Professor Mullins continues: “Some extraterrestrial civilizations may migrate to planetary systems of flyby stars

• Hansen and Zuckerman, Reference Hansen and Zuckerman2021

Orphan planet

The idea of advanced civilizations moving to other planets inspired Mullins to think about how extraterrestrial beings might travel. Then he realized that orphaned planets could provide a lift for extraterrestrial beings passing through their planetary systems.

In her essay “Orphan Planets,” Professor Irina describes how some planets may come to be orphaned. Such planets might be easier to colonize than a starship because they provide both constant gravity and a lot of space. It is also possible that water exists on or near the surface of an orphaned planet, providing an ideal location for alien creatures to create an undersea habitat.

Find a lift

Theoretically, aliens can hitch a ride on an orphan planet by waiting for such a planet to pass through the planetary system in which they live.

If the planet is large enough and far enough from its parent star, it could potentially house life, according to Mullins (2011).

Scientific studies suggest that the number of orphan planets may be greater than the number of stars in the Milky Way.

That increases the likelihood of orphan planets traveling through the outer reaches of planetary systems.

Once aliens have colonized those outer reaches of their system, they need only travel a short distance with their spacecraft to colonize such a passing orphan planet.

Take matters into your own hands

However, there is a disadvantage to this approach: it takes time to see if an orphan planet is headed toward Earth.

In such a dire situation—such as when Earth faces an existential threat—an advanced civilization could use technologies to ensure that its species travels to the passing orphan planet.

Create an orphan planet

It is possible (although speculative) that aliens could travel to a dwarf planet in their own planetary system and then release it from the influence of its parent star, so that the planet transforms into an orphan planet.

Aliens can then use advanced propulsion systems and gravitational pendulums to hurl Sedna objects out of their own planetary systems.

However, this approach is only for highly advanced alien civilizations. With the propulsion systems required to do so, they would be centuries ahead of our space technology.

A push from the mother star

Dwarf planets can also be thrown from their planetary systems by a dying parent star.

This occurs when the parent star transforms into a red giant or supernova. In this case, there is a reason for any aliens in the heart of the planetary system to flee.

In theory, they could switch relatively close to home to an object with an eccentric (oval-shaped) orbit.

That object takes them to the outer reaches of their planetary system where they can transfer to a dwarf planet which is later ejected from the planetary system by the dying parent star and thus becomes an orphan planet.

Means of transport, not a home

Some of the scenarios described above require advanced drive systems; others do not. In all scenarios, though, the result is the same: orphaned planets are wanderers through space on their own.

Therefore, we should see them as potential alternatives to interstellar travel, not as new homes for alien civilizations.

Because orphaned planets are not hospitable for long-term habitation due to decreasing heat production within their interiors and fewer resources available than planetary systems have to offer.

Thus, extraterrestrial civilizations would not make them their permanent home either, but only use them as a means of transport to reach and colonize other planetary systems.

Send

Once on an orphan planet, aliens can send their orphan planet into interstellar space using propulsion technologies, perhaps supplemented by gravitational pendulums, according to a new study.

Or they just have to wait for their orphan planet to reach another planetary system on its own.

Acceptable scenario?

Whether aliens move through the universe remains a mystery, though it is not an unthinkable scenario for Mullins.

Scientific studies have indicated that it is impossible to build ships that allow entire civilizations to travel between the stars, but humans instinctively want to save their asses, and other civilizations may feel the same way.

When stars die, advanced intelligent species will look for ways to escape. Since large ships are not an option, they will look for other methods.

Orphan planets with all their resources and oceans filled with water provide everything aliens need during their interstellar journeys.

Looking

Mullins believes that intelligent aliens may be capable of piggybacking on an orphaned planet, and she has begun to search for signs of their presence. She calls this search for migratory intelligent life (Mullins calls it: SMETI). Scientists traditionally look for techno signatures (traces of extraterrestrial technologies that hint at the presence of intelligent life) in the habitable zone of planetary systems containing a star that is similar to or smaller than our sun.

Even after sixty years of searching, we still haven’t found any evidence of extraterrestrial life. Some scientists believe that as alien civilizations become more advanced, they use their technologies to blend in with their environment and become difficult to detect at interstellar distances. But when such a civilization (of necessity) heads for other planetary systems, technologies have to be used that are a lot more striking and with that, it should also be a little easier to look for those aliens.

In addition, star-trapped orphan planets could also be good places to look for traces of life. Like the environment of dying stars; aliens that have fled on a dwarf or orphan planet can just be found there, or so the idea is. It does not make the traditional search for extraterrestrial life superfluous, Mullins emphasizes but can be seen as a supplement to it. “I would like to say that my research paper is a call to expand the SETI program.”

Finally, the research could also have implications for human beings because Mullins presents a form of transport that could not only be of interest to possible aliens but that could also benefit humanity. “Like aliens, humanity can use orphan planets to reach other planetary systems,” Mullins said. “That would be something for the distant future; when our space technology is much more advanced.