Computer simulations suggest that Pluto might have as many as ten undiscovered additional moons.
The planet already has five, so if this is true space is really crowded there, which might pose a problem for the New Horizons spacecraft that plans to fly past in 2015.
They will have to come up with a rule on exactly what could be called a moon.
The earth at times has more than one rock in orbit around it.
Good point – I was wondering about that myself. How big does a “rock” have to be to be considered a moon? And kind of ironic that Pluto, demoted from Planet to “Dwarf Planet”, leaves the Earth in the dust when it comes to moons. It would almost seem to me that any relatively large body orbiting the Sun which has moons of its own ought to be classified as a planet. But then I thought I read that at least one of the large asteroids has a “moon”. The whole issue is a bit murky…
Or another way to look at the New Horizon mission is that it will enter a target-rich environment.