Orbital motion of 1999 KW4 from December 2017 until July 2019 shown in helicentric reference frame. The asteroid makes two close flybys during this interval. The animation begins with an oblique view and then tilts to a perspective looking down on the plane of Earth's orbit from the north. The animation illustrates the unusually eccentric orbit and deep perihelion of only 0.200 au, which is inside the semimajor axis of Mercury. Close Earth encounters tend to be relatively long because they occur near aphelion when 1999 KW4's orbital motion is slow.