Have you ever woken up to a bad dream? The planet-killing kind with black holes, supernovas, and stuff? If yes, have you ever chewed over a real-time solution for if we ever were to face such a cosmic catastrophe in the world that we are living in right now? You are not alone.
Dangers of these sorts have been predicted millions of years in advance. But still, we cannot do much to evade it unless we move our solar system away from the threat. Stellar Engines do precisely this. A Stellar engine is a hypothetical, massive machine that can steer the solar system through the galaxy. This engine moves only the Sun, and the other objects attracted to it because of gravity follow it.
Picture an astronaut having their torch switched on in space: it would push them backwards sluggishly. This phenomenon occurs due to the momentum created by photons in a vacuum. The same notion applies on a humungous scale to the Shkadov thruster, the most basic stellar engine. The Shkadov thruster is a giant parabolic mirror that reflects Sun’s light in one direction and pulls it in the other; it operates like a rocket, but instead of using matter as fuel, it uses sunlight. The thruster needs to be over the poles of the Sun to avoid burning or freezing other planets with sunlight. This restricts our travel options as the solar system can only move vertically. The Shkadov thruster would approximately need 230 million years to move the orbit of the Sun by 100 light-years.
The Caplan thruster is another fascinating, efficient model of a stellar engine. It acts like a monstrous rocket, firing exhaust in one way to drive the engine and the entire solar system in the opposite direction. It uses massive electromagnetic fields to collect solar mass and separates them into hydrogen and helium. The accelerator and the reactor feed on these components. The helium is burned explosively in the thermonuclear fusion reactor. The force that propels our solar system comes from a jet of radioactive oxygen. A particle accelerator fires a stream of hydrogen back into the Sun, preventing the engine from colliding with the Sun and thereby pushing it in the direction we want it to go. This engine can move our Sun by 50 light-years in as little as a million years. This engine does consume the Sun, but it also extends its lifespan. With a lesser mass, the Sun burns more slowly, which helps to make the solar system habitable for many more years.
Stellar engines might also provide humans with the opportunity to evolve into an interplanetary species. Given that our Sun will eventually die, a transportation medium of this type might allow our posterity to travel to other stars and colonize them without incurring the perils of interstellar space.
