P/2011 S1 (Gibbs) is a periodic comet or an active centaur with a 25-year orbit around the Sun. Discovery. American astronomer, Alex R. Gibbs, reported the discovery of a new object from CCD images obtained from the reflector telescope from the Mount Lemmon Survey on 19 September 2011. Precovery images show that the object produced comet-like activity as early as September 2010, a year before its discovery.