Astrophysicist Matt Caplan might have been reading science fiction when he published a new paper in the journal Acta Astronautica, suggesting that moving the Sun could be the solution to a variety of possible problems.
Stellar engines, megastructures used to control the motion of a star system, may be constructible by technologically advanced civilizations and used to avoid dangerous astrophysical events or transport a star system into proximity with another for colonization.
This work considers two designs for stellar engines, for both human applications in the solar system and for advanced civilizations around arbitrary stars more generally, and presents analytic calculations of the maximum acceleration and deflection of a star in its galactic orbit.
The first is a large ‘passive’ solar sail, similar to that proposed by Shkadov, which we find produces accelerations of order for sun-like stars. The second ‘active’ engine uses a thermonuclear driven jet, as in a Bussard ramjet, which collects matter from the solar wind to drive He fusion. This engine requires additional mass to be lifted from the sun, beyond what is provided by the nascent solar wind, but may achieve accelerations up to producing deflections of 10 pc in as little as 1 Myr for a sun-like star.
While passive engines may be insufficient for catastrophe avoidance on short timescales, they can produce arbitrary deflections of a star in its galactic orbit over a stellar lifetime. Active engines are sufficient for retrograde galactic orbits or galactic escape trajectories, which we argue are useful to expansionist civilizations. These populations of stars may be candidates for observationally detecting megastructures.
The idea of moving stars has been around for a while in science fiction. In his classic 1928 novel Crashing Suns, Golden Age great Edmond Hamilton described the process by which the sun might be steered to a new location:
To accomplish this, to swerve their star from its course, the globemen made use of a simple physical principle...
The problem, then, was to increase their sun's rate of spin, and to accomplish this they gathered all their science. A mighty tower was erected over their city, on whose great top-platform were placed machines which could generate an etheric ray or vibration of inconceivable power, a ray which could be directed at will...
(Read more details about steering a star)