In late 2017 an interstellar object entered our solar system, hung out for a bit, and then left. It could fit inside a football field. It was turning in some way. It may or may not have accelerated. It had been wandering the Milky Way galaxy for millions, perhaps billions of years. We do not know what it is. Astronomers took to calling the object Oumuamua, which, loosely, means ‘scout.’ We do not know what it was. Nobody knows what it was. We only have theories. What we do have is a slowly building plan for what to do if this ever happens again. Here’s more from Phys.Org:
…observers began debating the issue of whether space agencies such as NASA should make plans for studying such an object if another should appear. In this new effort, the researchers studied the circumstances surrounding the appearance and departure of ‘Oumuamua and also that of other solar bodies such as asteroids or comets. They also looked at existing projects such as the ESP’s Comet Interceptor. They then developed a list of needs should a project be developed to create a probe capable of intercepting an interstellar visitor.
The researchers began with the assumption that such a mission would be based on research, not destruction. And that such research would entail taking photographs and using devices to learn more about the makeup of such an object. Because of that, they note, a probe would have to be built with such capabilities. They further suggest it would require a spectrometer sensitive to the wavelength range of 0.4 to 2.5 µm to discriminate between natural and artificially created materials.