3753 Cruithne It was not until 1997 that its unusual orbit was determined by Paul Wiegert and Kimmo Innanen, working at York University in Toronto, and Seppo Mikkola, working at the University of Turku in Finland. Cruithne is approximately in diameter, and its closest approach to Earth is , approximately thirty times the separation between Earth and the Moon. From 1994 through 2015, Cruithne made its annual closest approach to Earth every November. Although Cruithne's orbit is not thought to be stable over the long term, calculations by Wiegert and Innanen showed that it has probably been synchronized with Earth's orbit for
Near-Earth object list. NEOs are also catalogued by two separate units of the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA): the Center for Near Earth Object Studies (CNEOS) and the Solar System Dynamics Group. PHAs are currently defined based on parameters relating to their potential to approach the Earth dangerously closely. Mostly objects with an Earth minimum orbit intersection distance (MOID) of 0.05 AU or less and an absolute magnitude of 22.0 or brighter (a rough indicator of large size) are considered PHAs. Objects that cannot approach closer to the Earth (i.e. MOID) than , or are