Advanced alien civilisations could build a machine capable of moving a star – and we might be able to catch them in action.
The idea, thought up by Alexander Svoronos at Yale University, is called a Star Tug and would allow civilisations to avoid cosmic disasters.
“It’s a megastructure that can be used to move an entire star system,” says Svoronos. “If their star system is going to be in proximity of a supernova, they might want to try to avoid it.”
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The idea of moving stars isn’t new. In 1987, Russian physicist Leonid Shkadov first described his Shkadov thruster, which would use a giant mirror to reflect a star’s light back on its surface and produce thrust, enabling modest speeds over a long period of time.
Svoronos’s idea, however, is somewhat different. Assuming the star to be moved is the same mass as the sun, it would involve placing a large structure, weighing at least a fifth the mass of our moon, as close as 10,000 kilometres from the star. The gravitational pull of the object, although small, would drag the star towards it, producing acceleration.
The structure would have thrusters, allowing it to move and pull the star along with it. Svoronos estimates that this acceleration could enable speeds of 0.1 per cent the speed of light in 5300 years, and 10 per cent in 38 million years – up to a million times faster than a Shkadov thruster.
One complication is that the Star Tug relies on extracting material from the star itself to power its engines via nuclear fusion. This could be done with giant space elevators, but they might struggle to survive so close to a star. “You need ridiculously strong materials,” says Anders Sandberg at the University of Oxford’s Future of Humanity Institute.
If it were possible, however, the Star Tug could enable an advanced alien civilisation to move its solar system to another part of its galaxy, colonising other systems along the way, or perhaps relocate to a different galaxy altogether. “You can actually expand to another galaxy over hundreds of millions of years,” says Svoronos.
While beyond humanity’s ability for now, we could in theory look for alien Star Tugs. Most stars rotate around the galaxy in the same direction, but some don’t. “We think they’re natural,” says Sandberg. “But if you see a lot of them, that might be a hint that something weird is going on.”
Acta Astronautica
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