Introduction

In April 2006, astronomers of the Royal Astronomical Society (RAS) were doing a high-resolution survey of the Andromeda Galaxy (M31) when they discovered a new form of star cluster, the extended cluster (Huxor, et. al, 2006) These clusters have a similar density to traditional globular clusters (GCs), but have a larger half-light radius, Rh, meaning that they are more extended than GCs. Their V-I colors are consistent with the metal poor stars in the globular cluster populations, at least in M31, without evidence of young main-sequence stars. These clusters help to fill a gap between traditional GCs and dwarf spheroidal galaxies (dSp), the first having almost no dark matter, the other being highly dominated by dark matter. This gap is currently being filled by a few recently-discovered cluster types: extended clusters and faint fuzzies. There have been relatively few postulations on the formation of extended clusters. There are two dominating theories: that they are the remnant of dwarf spheroidals that collided with the galaxies, or they are the remnants of tidally stripped dwarf spheroidals. Since only a limited number of these clusters have been found only in M31, no solid conclusions on their formation have yet been made.