The Breakthrough Starshot initiative aims to send small, lightweight probes to a nearby star system using photons emitted by a powerful ground-based laser array. If a similar technology were employed by an extraterrestrial civilization to send probes toward our solar system, the ability to detect these probes would depend on a few critical factors.
Firstly, the size and reflectivity of the incoming probe would be crucial. Breakthrough Starshot proposes sending “Starchip” probes, designed to be a few centimeters across and potentially covered in reflective sails. Such small and reflective objects are challenging to detect with current technology as they do not emit their own light and would be dimmer than many natural celestial bodies in the sky.
Secondly, the speed of the probe would affect detection. The Breakthrough Starshot’s target speed is a significant fraction of the speed of light—around 20%—which means the probe would move rapidly across the sky. Our telescopes’ ability to track such fast-moving and faint objects depends on the development of more advanced tracking and detection systems.
Current ground and space-based telescopes have been mainly optimized for detecting relatively large and slow-moving objects, like planets and asteroids within our solar system, and very distant and bright objects such as stars and galaxies. Detecting an interstellar probe would require developing new observational strategies and technologies specifically designed to spot small, fast-moving, and potentially non-emissive objects.
In summary, while detecting probes launched from another star system using technology similar to Breakthrough Starshot is theoretically possible, it would present significant challenges with our current observational capabilities. Advancements in telescope technologies and detection methods would be necessary to increase the chances of detecting such an interstellar visitor.