The Ramans do everything in threes.

Great reference, thank you. I'd forgotten that trait, need to read the book again.

Even if something else comes along, maybe this one was special. It acted very strangely. What if we detect 5 more in the coming century, but none does that interesting "accelerating without pluming" thing?!

Astronomers think we get several inside Earth's orbit each year, and interceptable ones come in on a weekly basis.

Detecting them is the tricky part