A second moon was discovered in 1986 which was given the name Cruithne. It follows a horseshoe shaped path. There have since been two others which may or may not be categorised as moons. They are J002E3 and 2002 AA29. These two recent discoveries may be considered to be a couple of lumps of rock and not moons. It is also suggested that Cruithne is not a moon but a companion to earth, while thay both orbit the sun. So the answer is either 1 or 4 at the moment, until some clever people make their minds up.