In about 5 billion years, the Sun will leave the main sequence and become a red giant. It will expand and turn into a shiny, malevolent ball and consume and destroy Mercury, Venus, Earth and perhaps Mars.
Can Humanity Escape the Sun’s Red Giant Phase? Extraterrestrial civilizations (ETCs) may already be facing this existential threat.
Could they have avoided it by migrating to another star system without the use of spacecraft?
Universe Today readers are well aware of the difficulties of interstellar travel. Our nearest neighbor solar system is the Alpha Centauri system.
If humanity had to flee an existential threat in our solar system, and if we could identify a planet in Alpha Centauri, it would still take four years to get there if we could travel at the speed of light!
At our technical level it still takes us five years to orbit Jupiter. There’s a lot of talk about generation starships, where humans can live for generations on their way to a distant habitable planet.
Those ships don’t need to reach anywhere near the speed of light; Instead, entire generations of humans will live and die on a journey to another star that takes hundreds or even thousands of years. It’s fun to think about at this point but pure fantasy.
Is there any other way we, or other civilizations, can escape from our ruined homes?
author of a new research article in International Journal of Astrobiology says that ETC cannot require a starship to escape existential threats and travel to another star system.
They could instead use free-floating planets, also known as rogue planets. The article is “Migrating extraterrestrial 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 propose that extraterrestrial civilizations could use free-floating planets as interstellar transport to reach, explore, and colonize planetary systems,” writes Romanovskaya. And when it comes to discovering other civilizations, these efforts may leave behind technological signatures and artifacts.
“I propose potential technological signatures and artifacts that could be produced by extraterrestrial civilizations using free-floating planets for interstellar migration and interstellar colonization, as well as strategies for exploring their technological signatures and artifacts.”
It is possible that rogue planets, either in the Milky Way or some hundreds of billions of other galaxies, carry their life with them in subsurface oceans kept warm by radiogenic decay.
Then if they meet a star and are gravitationally bound, that life has effectively used a rogue planet to make itself, as expected, far more hospitable. So why can’t any civilization imitate that?
We think of free-floating planets as dark, cold and inaccessible. And they are unless they have warm subsurface oceans. But they also offer some advantages.
“Free-floating planets can provide constant surface gravity, vast amounts of space and resources,” Romanovskaya writes. “Free-floating planets with surface and subsurface oceans may provide water as a consumable resource and for protection from space radiation.”
An advanced civilization could also engineer the planet to be of even greater benefit by operating and developing energy sources. Romanovskaya suggests that advanced civilizations will already be using it if we are on the verge of using controlled fusion, which could turn a cold rogue planet into something that could support life.
The author outlines four scenarios where ETC can take advantage of rogue planets.
The first scenario involves a rogue planet passing through an ETC’s home world. The number of times this can happen is normally linked to the number of rogue planets.
So far, we don’t know how many there are, but there certainly are some. In 2021, a team of researchers discovered between 70 and 170 rogue planets, each the size of Jupiter, in a region of the Milky Way. And in 2020, a study suggested that there may be up to 50 billion in our galaxy.
Where do they all come from? Most are ejected from their solar system due to gravitational events, but some can form through accretion as stars.
Another source of rogue planets is the Oort cloud of our solar system. If other systems also have a cloud of such objects, they could be an abundant source of rogue planets ejected by stellar activity.
Romanovskaya writes: “Stars 17 times the solar mass after main-sequence evolution, as well as supernovae from a 720 times solar mass ancestor, can eject Oort-cloud objects from their systems so that such objects form. Go unbound from your host stars.”
But how often can an ETC, or our civilization, expect a rogue planet to come close to a hitchhiker? A 2015 study showed that the binary star W0720 (Scholz’s star) passed through our solar system’s Oort cloud about 70,000 years ago.
While that was a star and not a planet, it showed that the objects passed relatively close by. If studies predicting billions of free-floating planets are correct, some of them probably passed by the Oort cloud, or long before we had the means to detect them.
The Oort Cloud is far away, but a sufficiently advanced civilization might have the ability to visit a rogue planet by coming and going.
The second scenario involves using technology to bring a rogue planet closer to civilization’s home. With enough technology, they can pick up an object from their own Oort cloud assuming they have one and use a propulsion system to direct it toward a safe orbit near their planet.
With enough time, they can adapt the object to their needs, for example, by building underground shelters and other infrastructure. Maybe, with enough technology, they can 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. Romanovsna uses Sedna, the dwarf planet in our Solar System, as an example.
Sedna has a highly eccentric orbit that takes it from 76 AU to 937 AU from the Sun in about 11,000 years. With enough technology and lead time, a Sedna-like object can be turned into an escape ship.
The author notes that “civilizations capable of doing this would be advanced civilizations that have already discovered their planetary systems to a distance of at least 60 AU from their host stars”.
There are lots of potential problems. Bringing a dwarf planet from distant regions of the Solar System into the inner Solar System could disrupt the orbits of other planets, posing all kinds of dangers.
But the danger is lessened if a civilization around a post-main sequence star has already migrated outward along the changing habitable zone. Romanovskaya discussed in more detail the energy required and the time required 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 where objects will be ejected from the system, rather than gravitationally bound to the dying star.
If an ETC can accurately determine when these objects will be ejected as rogue planets, they can preform it and eject it from the dying solar system. This can be extraordinarily dangerous, as periods of violent mass loss from the star pose a great danger.
In all of these scenarios, the rogue planet or other body is not a permanent home; It is a lifeboat.
“For all of the above scenarios, free-floating planets may not serve as a permanent means of avoiding existential threats,” the authors explain. “Because of the decreasing heat in their interior, such planets eventually fail to maintain 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 to me, for example, and no free solar power. There is no season and there is no night and day. There are no plants, animals or even bacteria. They are simply a means to an end.
“Therefore, instead of making free-floating planets their permanent homes, extraterrestrial civilizations will use free-floating planets as interstellar transport to reach and colonize other planetary systems,” writes Romanovskaya.
In his article, Professor Romanovskaya speculates about where this could lead. She envisions a civilization that does this more than once, not to escape a dying star but to spread across a galaxy and colonize it.
“In this way, parent-civilizations can form unique and autonomous daughter-civilizations living on different planets, moons or regions of space.
“A civilization of cosmic hitchhikers would act as a ‘parent-civilization’, spreading the seeds of ‘daughter-civilizations’ as their colonies in planetary systems,” she writes. “This applies to both biotic and post-biotic species.”
Humanity is only in the early stages of protecting itself from devastating asteroid impacts, and we cannot yet manage our planet’s climate with any level of stability. So it seems too far-fetched to think of using rogue planets to keep humanity alive. But Romanovskaya’s research is not about us; It’s about locating other civilizations.
All this activity can create technical signatures and artifacts that indicate the presence of ETC. The research article explains what they could be and how we can detect them. Rogue planets used as lifeboats can create technological signatures such as electromagnetic emissions or other phenomena.
An ETC can use solar sails to control a rogue planet or use them on a spacecraft launched from a rogue planet after reaching its destination. In any case, solar sails produce a technical signature: cyclotron radiation.
Maneuvering a spacecraft or a rogue planet with a solar sail would generate “…cyclotron radiation due to the interaction of the interstellar medium with the magnetic sail”.
Infrared emissions emitted as waste heat by an ETC on a rogue planet could be another technological signature. Excessive amounts of infrared or unnatural changes in the amount of infrared can be recognized as a technical signature.
Infrared may be emitted unevenly across the surface of the planet, indicating the underlying engineering or technology. An unusual mix of different wavelengths of electromagnetic energy can also be a technical signature.
The atmosphere, if one were present, could also bear a technical signature. Depending on what was observed, it may contain evidence of terraforming.
For now, astronomers don’t know how many rogue planets there are or if they are concentrated in certain regions of the Milky Way. We are on the starting line when it comes to figuring these things out. But soon, we may have a better idea.
The Vera Rubin Observatory should see its first light by 2023. This powerful observatory will image the entire available sky every few nights, and it will do so in fine detail. It has the biggest digital camera ever: a 3.2 gigabyte CCD.
Vera Rubin would be especially good at locating clients, i.e. anything that changes status or brightness in a matter of days. This would be a good chance to find any interlopers like rogue planets approaching our solar system.
There is a strong possibility that some of those rogue planets will exhibit unusual emissions or shocking phenomena. Scientists will probably puzzle over them like they did on Oumuamua.
Another civilization more advanced than us may have already faced an existential threat from its dying star. Maybe they made a daunting effort to capture a rogue planet and engineer it to suit their needs.
They may have already boarded it and launched it toward a distant, stable, long-lived yellow star with rocky planets in their habitable zone. Maybe they are wondering if there is any life at their destination and how to get to them after their long journey.
This article was originally published by Universe Today. Read the original article.
