Pluto and Charon are in the middle, orbiting around their common center of mass. The four smaller moons orbit around them.
When you begin a new research project, you usually have expectations about where it will lead. Most projects take you or less to the expected destination. Some go nowhere. However, every now and then a project picks you up and makes you feel like you’re just coming along for the ride.
Today, in the journal Nature, we have published the results of a research project that fits solidly into the third category.
Our original plan was straightforward. We had recently discovered two small moons of Pluto, now known as Kerberos and Styx. We wanted to publish a short discovery paper that would just cover the basics: How did we find the moons? What are their orbits? How big are they? What are the implications of the discovery?
The Pluto system had other ideas.
Pluto also has two much brighter moons nearby, Nix and Hydra. They had been discovered years earlier and much had been written about them. I had no reason to think there was anything new to be said about either of them. For me, they could just ...