In about 5 billion years, the Sun will leave the main sequence and become a red giant. It will expand and turn into a hot, malicious ball and devour and destroy Mercury, Venus, Earth and possibly Mars. Can humanity survive in the phase of the red giant of the Sun? Alien Civilizations (ETC) may have already faced this existential threat.
Could they have survived by migrating to another star system without the use of spacecraft?
Readers of Universe Today are well aware of the difficulties of interstellar travel. The nearest neighboring solar system is the Alpha Centauri system. If humanity had to escape an existential threat to our solar system, and if we could identify a planetary home in Alpha Centauri, it would still take us more than four years to get there – if we could travel at the speed of light!
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It still takes us five years to get to orbit Jupiter at our technological stage. There is a lot of talk about generational starships, where humans could live for generations on their way to a distant habitable planet. These ships should not reach almost the speed of light; instead, generations of people would live and die on a journey to another star that would take hundreds or thousands of years. It’s fun to think, but at this point it’s pure fantasy.
This is an image of the Nauvoo ship of the “Space” generation. The ships of generations are currently the subject of science fiction. Image Credit: Legendary TV distribution.
Is there another way for us or other civilizations to escape their doomed homes?
The author of a new research paper in the International Journal of Astrobiology says ETCs may not need starships to escape existential threats and travel to another star system. Instead, they could use free-floating planets, also known as rogue planets. The article is “Migrating alien civilizations and interstellar colonization: implications for SETI and SETA.” The author is Irina Romanovskaya. Romanovskaya is a professor of physics and astronomy at Houston Community College.
“I suggest that extraterrestrial civilizations use free-floating planets as interstellar transport to reach, explore and colonize planetary systems,” Romanovskaya wrote. And when it comes to searching for other civilizations, these efforts can leave techno-signatures and artifacts. “I suggest possible techsignatures and artifacts that can be produced by extraterrestrial civilizations using free-floating planets for interstellar migration and interstellar colonization, as well as strategies for searching for their technosignatures and artifacts,” she said.
It is possible that the deceptive planets, either in the Milky Way or some of the other hundreds of billions of galaxies, will bring their own life into the subterranean oceans, kept warm by radiogenic decay. Then, if they meet a star and connect by gravity, this life has effectively used the planet cheater to move, hopefully, to somewhere more hospitable. So why can’t a civilization imitate that?
We believe that free-floating planets are dark, cold and inhospitable. And they are, unless they have warm underground oceans. But they also offer some advantages. “Free-floating planets can provide constant surface gravity, large amounts of space and resources,” Romanovskaya wrote. “Free-floating planets with surface and subterranean oceans can provide water as a consumable resource and protection from cosmic radiation.
An advanced civilization can also create the planet for even greater advantage by managing it and developing energy sources. Romanovskaya suggests that if we are on the verge of using controlled fusion, then advanced civilizations may already be using it, which could turn a cool cheating planet into something that can sustain life.
The author outlines four scenarios in which ETCs could benefit from fraudulent planets.
The first scenario involves a rogue planet that happens to pass by the home world of ETC. How often this can happen is related to the number of deceptive planets in general. We don’t know how many there are yet, but there are certainly some. In 2021, a team of researchers announced the discovery of between 70 and 170 deceptive planets, each the size of Jupiter, in a region of the Milky Way. And in 2020, a study suggests that there may be up to 50 billion of them in our galaxy.
Where does everyone come from? Most are likely ejected from their solar systems due to gravitational events, but some can be formed by accumulation, as stars do.
Another source of deceptive planets is the Oort cloud of our solar system. If other systems also have a cloud of objects like this, they can be an abundant source of deceptive planets ejected by stellar activity. Romanovskaya writes: “Stars with 7-7 times the solar mass, evolving after the main sequence, as well as a supernova from a predecessor with 7-20 times the solar mass, can eject objects from the Oort cloud from their systems, so that such objects become unrelated to their host stars. “
But how often can the ETC or our civilization expect a rogue planet to get close enough to get closer to a stop? A 2015 study showed that the binary star W0720 (Scholz’s star) passed through the Oort cloud of our solar system about 70,000 years ago. Although it was a star, not a planet, this shows that the objects pass relatively close. If studies that predict billions of free-floating planets are correct, then some of them probably passed close or right through the Oort cloud long before we had the means to find them.
The Oort cloud is far away, but a sufficiently advanced civilization may have the ability to see an approaching rogue planet and go out and meet it.
Reduction; the inner solar system (top left), the outer solar system (top right), the orbit of Sedna (bottom right) and the inner edge of the Oort cloud (bottom left). Image Credit: NASA
The second scenario involves the use of technology to direct the rogue planet closer to the home of civilization. With enough technology, they could pick an object from their own Oort cloud – assuming they have one – and use a propulsion system to steer it into a safe orbit near their planet. With enough time to implement, they could adapt the site to their needs, for example by building underground sheds and other infrastructure. Maybe with the right technology they could change or create an atmosphere.
The third scenario is similar to the second. It also includes an object from the outer solar system of civilization. Romanovskaya uses the dwarf planet Sedna in our solar system as an example. Sedna has an extremely eccentric orbit that takes it from 76 AU from the Sun to 937 AU in about 11,000 years. With enough technology and execution time, an object like Sedna can be turned into a lifeboat. The author notes that “civilizations capable of doing so would be advanced civilizations whose planetary systems have already been studied at distances of at least 60 AU from their host stars.”
The artist’s concept of Sedna, a dwarf planet in the solar system that is only 76 astronomical units (Earth-Sun distances) from our Sun. Credit: NASA / JPL-Caltech
There are many potential problems. The transfer of a dwarf planet from the far reaches of the solar system to the inner solar system can disrupt the orbits of other planets, leading to all sorts of dangers. But the dangers are mitigated if a civilization around a star after the main sequence has already migrated outward with the changing habitable zone. Romanovskaya discusses the necessary energy and the necessary time in more detail in her article.
The fourth scenario also includes objects such as Sedna. When a star leaves the main sequence and expands, there is a critical distance at which objects will be ejected from the system instead of remaining gravitationally connected to the dying star. If the ETC could determine exactly when these objects would be ejected as rogue planets, they could prepare it in advance and get it out of the dying solar system. This can be extremely dangerous, as periods of forced loss of mass by the star pose a huge danger.
Three rings of ejected gas float away from an aging star called V Hydrae, seen in this fake radio image from the large millimeter / submillimeter Atacama massif in Chile. Image credit: ALMA
In all these scenarios, the planet deceiver or other body is not a permanent home; this is a lifeboat. “In all of the above scenarios, free-floating planets may not serve as a permanent means of escaping existential threats,” the author explains. “Due to the declining heat production inside, such planets end up failing to support oceans of liquid water (if such oceans exist).”
Free-floating planets are also isolated and have fewer resources than planets in the solar system. There are no asteroids for digging, for example, and free solar energy. There are no seasons and no night and day. No plants, animals or even bacteria. They are just a means to an end. “Therefore, instead of turning free-floating planets into permanent homes, extraterrestrial civilizations would use free-floating planets as interstellar transport to reach and colonize other planetary systems,” Romanovskaya wrote.
In his article, Professor Romanovskaya speculates on where this could lead. She imagines a civilization that does this more than once, not to escape a dying star, but to spread throughout the galaxy and colonize it. “In this way, the parent civilization can create unique and autonomous daughter civilizations inhabiting different planets, moons or regions of space.
A space hitchhiking civilization would act as a “parent civilization” spreading the seeds of “daughter civilizations” in the form of its colonies in the planetary …
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