Shaped like an elongated cigar, by the time it was spotted it had already zipped by our own Sun, performed a slick hairpin turn, and begun hurtling off in another direction.
Two things in particular fixated scientists.
The first was its mysterious acceleration away from the Sun, which was hard to reconcile with many ideas about what it might have been made of.
The second was its peculiar shape – by some estimates, it was 10 times as long as it was wide. Are Aliens Patrolling Us? More Interstellar Visitors Now in the Solar System