The magnitude 10 comet was discovered by Alan Watson (Melbourne) on STEREO-B satellite images taken on December 8, 2008. It was noticed by Maik Meyer that the orbital elements of the new comet was identical to comet P/2003 K2 (Christensen), which was due to reach the perihelion on January 8, 2009. The identity was confirmed by Brian Marsden, who showed that the perihelion passage data needed to be adjusted by 22 days. The orbital elements of the comet P/2008 X4 (Christensen) indicate a perihelion passage on December 19, 2008 at a distance of approximately 0.53 AU, and a 5.66 year period.