Could the Breakthrough Starshot probes be detected in their taget system by modern or near-future technology?

The Breakthrough Starshot is a method of robotic interstellar exploration by launching thousands of small centimeter-sized probes, each equipped with a 4 x 4 meter light-sail. Thanks to their small weight, they can achieve speeds of up to 20% lightspeed even with technology currently available to us. As collision with even the smallest dust particles in space could destroy the probes at such speeds, thousands are to be launched so at least a few can arrive to their destination.

Let's assume that an intelligent civilization lives on the planet we launch these probes to, and they have a level of technology similar to ours, or at most only slightly more advanced. (Or that they launch such probes at us, arriving here within the next few years)

Could they be detected in any way? If so, could it be found out that they are made by intelligent beings in another solar system?

• if success only depends on a very narrow margin, the probes might be slightly larger (not by orders of magnitude!) or their speed might slightly differ from the 0.2 c in the question.
• I would guess they would be impossible or nigh-impossible to detect. Would this change if the arrival of such probes was theorized/expected, and special equipment was made beforehand to scan for them? (just as we have built Seti-radiotelescopes expecting aliens to try to contact us by radio)
• I would guess the probes would just fly by the planet making photos, taking measurements, and sending them home, and they wouldn't hit the planet. (they are not designed to slow down in the target system). If there is no other way to detect them, would this change if one (or a few) of them actually hit the planet? I would guess they would produce some gamma rays and such, but their small size would make them far from being catastrophic. Would such a crash be even detectable, and could it be assumed it was not a natural phenomena?

posted over 4 years ago

vsz‭

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