Supposing that it does become part of a new star, and some "nearby" civilization had sufficiently precise instruments...would that be a detectable anomaly? Like some atoms of Plutonium still haven't decayed, and isn't that weird that Plutonium's spectral signature is present in this new star? Or is that just something that happens because some plutonium is created in a supernova and might just have been floating around anyway.

Quite. It will hit the occasional something, eventually. If nothing else it will be mildly bathed in radiation of some sort.

It's going to hit gas that will slowly but inexorably sputter it to nothing.

From what I recall, one of the hazards of long term space travel is that nearly any material will start sublimating atoms in the hard vacuum of space, with things like cosmic rays adding to the woes. Some over time it will start deteriorating.

Not sure about “melting” into an amorphous mass, I guess in theory the probes gravity could do that, but I would imagine even the tiniest force would disturb that and dissipate it.

One issue is that over long enough timeframes, even atoms that we consider stable will decay - particularly ones that are heavier than iron, which will decay towards iron or nickel. That decay will eventually compromise the structure of the probes.

> It's expected never to encounter any other object in all eternity.

This is read as "near zero" rather than "no chance". "Expected" is a word of uncertainty.

I think the rough napkin math would be: take the volume that the probe will sweep through and multiply it by the volume of matter in the universe/volume of the universe.

Space is well named.

It's got a very long time to do so. Like how a bowl of water evaporates at room temperature.

Heat ray from a passing flying saucer?

Radiation?