The star formation history ( SFH ) of the Pegasus dIr , a likely Local Group member at 0.95 Mpc from the Milky Way , is investigated .
We characterize the SFH by two basic functions : the star formation rate , \psi ( t ) , and the chemical enrichment law , Z ( t ) .
It has been derived by comparing the color-magnitude diagram of the resolved stars in Pegasus , with a total of 189 model diagrams produced with different \psi ( t ) and Z ( t ) laws .

The models in better agreement with the data indicate that star formation began in Pegasus about 15 Gyr ago and was larger , on average , during the first half than during the second half of the galaxy ’ s life .
During the most recent epoch , for which the SFH can be obtained with much better time resolution , the star formation seems to be produced in a bursting mode .
This may have been the case for the whole life of the galaxy , although the resolution in time towards older epochs is not good enough to actually detect it .
As for the chemical enrichment law , the best way to account for the observed metallicity of the galaxy ( Z _ { f } = 0.002 ^ { +0.002 } _ { -0.001 } ) is that it suffered a prompt initial chemical enrichment .
This would be the case if infall was important , at least during the primeval epoch of galaxy evolution and points to a picture in which the galaxy began forming stars and enriching its interstellar medium in an early phase of collaps , when a lot of gas had still to be added to it .

Pegasus and NGC 6822 are the only dIrs for which the kind of analysis presented here has been done .
The fact that , like Pegasus , NGC 6822 also shows an important old to intermediate-age stellar population indicates that the Baade ’ s sheet observed in most dIr , may in fact be the signature of an important population of old stars and suggest that dIr actually are old objects populated by large numbers of old stars .

The mass in stars and stellar remnants is derived from average of the best model SFHs obtained .
The percentage of dark matter in Pegasus that can not be accounted for with stellar remnants or with an extrapolation of the Kroupa et al . IMF down to \sim 0.1 M _ { \odot } turns out to be \sim 92 \% .