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I'm not convinced we would be able to view any of those. The only exoplanets we've been able to directly image are huge gas giants that emit a ton of infrared l

I'm not convinced we would be able to view any of those. The only exoplanets we've been able to directly image are huge gas giants that emit a ton of infrared light. A massive solar sail will likely be much smaller and emit a lot less light. See here for a list with images to understand the level of detail we're getting: https://en.wikipedia.org/wiki/List_of_directly_imaged_exoplanets https://en.wikipedia.org/wiki/List_of_directly_imaged_exopla... I'd think you can easily have galaxy-hopping civilizations that would still be orders of magnitude less noticeable than these planets.

dredmorbius 4y ago
And most exoplanets are observed indirectly: doppler effects on the central star's light, occlusions of the central star's light measured through variances in the observed light from that star, and in a few cases absorption spectra of the exoplanet's atmosphere, again, by occlusion of the central star. All occlusion observations require orbital planes which are aligned such that they're viewable from our solar system, further reducing observable planets. And yes, there are a very few exoplanets which have been directly observed, but those are very much the exception. Detecting any signals or emissions of a technological alien race would be exceedingly difficult even at near range. Though mention of possible rocket systems and the fact that these are directional suggests that one of the more likely signals to be detected might be a decelerating ship, or ships, approaching the Solar System directly.