The strangest thing about the planet is the location of its orbit. The planet orbits its star at a distance of about 900,000 miles, which is about the diameter of the sun and other G-class stars. This is an orbit which places the planet more than 30 times closer to its sun than the planet Mercury is to our sun. The planet is so close to its star that it must be a kind of lava world too hot for life.
Depiction of Kepler-78b
Scientists are baffled by how a planet of this size could exist in this orbit, and the Science Daily article on the discovery is entitled Lava World Baffles Astronomers: Planet Kepler-78b 'Shouldn't Exist.' The article says: “When this planetary system was forming, the young star was larger than it is now. As a result, the current orbit of Kepler-78b would have been inside the swollen star.” It then quotes astronomer Dimitar Sasselov as saying this about the planet: "It couldn't have formed in place because you can't form a planet inside a star. It couldn't have formed further out and migrated inward, because it would have migrated all the way into the star.”
How, then, can we explain the orbit of the planet? Perhaps it is time for an audacious hypothesis.
The hypothesis I propose is this: Kepler-78b may be the result of intelligent extraterrestrial planet movers who deliberately moved the planet from a more distant orbit to its current orbit very close to the sun it orbits. The planet may have originally been a much larger planet (possibly a gas giant planet). It may have been deliberately moved to the orbit close to its star, for the sake of stripping off its gaseous outer layers, and leaving behind an inner core of dense metals, metals needed by the civilization that moved the planet.
Before explaining why this hypothesis may make sense, I need to first explain why the idea of an intelligent species moving around a planet in its solar system may be much less outrageous than it may seem at first.
Astronomers say that the universe is nearly 14 billion years old, but mankind is only a few million years old. Given that the age of the universe is several thousand times greater than the age of man, and that there are more than 1,000,000,000,000,000,000,000 stars that could support life-bearing planets, many astronomers suspect that intelligent life probably arose long, long ago on many planets. Some astronomers have looked for signs of gigantic engineering that might have been performed by civilizations millions of years more advanced than ours: projects such as the creation of a Dyson Sphere, a spherical structure that surrounds a star to capture as much of its energy as possible.
In this context, the idea of a civilization with the power to move planets in its solar system does not seem too outrageous. Such godlike abilities are what we would expect to see in a technical civilizations many thousands or millions of years more advanced than ours.
Having looked at such a context, let us look at the hypothesis of a civilization moving a planet within its solar system, concentrating on two things: feasibility and motive. We will first look at whether a highly advanced civilization could possibly accomplish such a task, and then look at whether it would have a good motive for such a task.
The Feasibility of Moving A Planet
When looking at the idea of a civilization moving a planet in its solar system, you might first imagine the civilization attaching a giant rocket to a planet. Judging such a thing to be totally impractical, you might then dismiss the possibility of moving a planet. But there would be much easier ways for a civilization to go about moving a planet. One way would be for it to use other astronomical objects as projectiles to force a planet out of its orbit, into a different orbit.
Consider our solar system. We know that near Jupiter is an asteroid belt. We also know that Jupiter has dozens of moons, some of them a good fraction of the mass of the planet Mercury. In the distant future we might be able to accelerate asteroids, and use them as projectiles. Such projectiles could be launched towards Jupiter, to help nudge it out of its orbit. We could also launch projectiles towards the moons of Jupiter, causing them to crash into Jupiter, helping to nudge Jupiter out of its orbit.
The formula for kinetic energy is very simple:
Kinetic Energy = ½ * mass * (velocity * velocity)
This means that every time you double the velocity of a projectile, you are multiplying by four times its kinetic energy; and if you increase the velocity by ten times, you increase the kinetic energy by a hundred times. So if a super-advanced extraterrestrial civilization were to find some way of accelerating asteroids to a very high speed, the civilization might then have a very powerful way of rearranging the orbits of gas giant planets in its solar system. The mass of asteroids could be leveraged to move around moons orbiting a gas giant, causing them to crash into the gas giant; and the mass of those moons could then be leveraged to move around a gas giant itself.
The feasibility of re-positioning a gas giant would all depend on how fast the civilization was able to accelerate asteroids. Once the civilization developed a very fast way of accelerating asteroids, it would have the key to rearranging the orbit of a planet in its solar system. And there is every reason to think that a very advanced civilization would have the ability to accelerate asteroids to a high speed (ordinary nuclear rockets or matter/antimatter rockets would be sufficient, without any need for exotic physics).
It would seem, therefore, that a project of rearranging the orbital position of a gas giant planet within its solar system is something that should be feasible for a technical civilization many thousands of years more advanced than ours.
The Motive for Moving a Planet
But what about motive? Why would a super-advanced civilization want to move a gas giant close to its star? The motive might be simple: to acquire more metals that the civilization needed.
Consider the metal demands of a civilization thousands or million of years more advanced than ours. Such a culture might have an insatiable demand for metals. It might have already tapped out its planet for metals, and have already mined its asteroids for metals. Such a culture might need billions of tons more for any of a thousand possible projects, such as the building of more space colonies or the building of something like a Dyson Sphere.
Gas giant planets are believed to have dense metallic cores, as shown in the diagram below of the structure of Jupiter.
What would happen if an extraterrestrial civilization were to move a gas giant planet near its sun? Some of the “hot jupiter” planets located close to stars are called “puffy planets,” because their diameter is several times greater than Jupiter, even though they are only about the mass of Jupiter. Such planets have puffed-up, superextended atmospheres caused by all the solar heat they are receiving in their orbits close to a star. If a gas giant was moved sufficiently close to a star, the hot temperature would cause the planet to lose its gas atmosphere altogether. The gaseous outer parts of the planet would become so super-heated that the gases would diffuse away from the planet. What would be left would be a metallic core, which the civilization could then use as an endless supply of metal to meet its demands. The remaining planet in such an orbit would resemble Kepler-78b.
We therefore have a plausible motive for why an extraterrestrial civilization might wish to move a gas giant very close to its sun: to acquire a gigantic source of accessible metals, a source that would take millions of years to exhaust.
The hypothesis I have suggested here would be bolstered if we were to find an Earth-sized planet in the habitable zone of the solar system of Kepler 78b. If such a planet is never found, we will be able to exclude the hypothesis that there is an intelligent race in this solar system. Until we know whether there are any habitable planets in this solar system, the hypothesis of a super-advanced race that has engaged in planet moving will remain a fascinating possibility to explain the strange orbit of Kepler-78b.
Postscript: Some scientists have concluded that moving planets is feasible, and the astrophysicist Neil deGrasse Tyson says he sees no reason why we can't start shifting planets around. But the optimum technique would probably not be the rather crude technique I suggested of smashing asteroids or moons directly into a planet. There is a better technique described by this paper "How to Move a Planet," written by Paul Birch, and published in the Journal of the British Interplanetary Society. The technique involves what is called an accelerated mass stream, which would travel in an orbit between a planet's star and the planet itself, and make use of what is called a gravitational assist or gravitational slingshot to achieve greater acceleration. The mass stream would pass near the planet, but not directly crash into it. Such a mass stream could slowly move the planet by means of a gradual transfer of angular momentum.