Alien civilizations might re-engineer their stars by building giant structures around them to give their planets a longer lifespan. Researchers involved in the search for extraterrestrial intelligence, or SETI, have suggested many times that technologically-advanced aliens might build structures we can see from Earth, such as Dyson swarms, objects surrounding a star to capture as much of its energy as possible.

A few other SETI researchers have suggested that instead of just trying to harvest solar energy from their host star, really ambitious alien civilizations could, in theory, actually blow material away from the star to make it live longer.

And that effort to buy the civilization another few billion years of survival might also be visible to astronomers here on Earth.