Pluto discovered

Pluto, you have been discovered twice:
First a wandering speck, now a wondrous world;
And furthermore, indeed, discovered thrice -
We find it's clear the moon with which you're hurled
And spun in fact is no mere satellite,
For as around the Sun you jointly trip
You one the other tug as requisite
And each the other hold in common grip
To justify the name of binary
Wherein you dance in dual finery.
What further marvels yet do you portend,
Presiding pregnantly where planets end!