This is the colour-magnitude diagram and spatial distribution of Boötes I dSph.
My focus is primarily on the stellar populations in ultra faint dwarf (UFD) galaxies and dwarf spheroidal (dSph) galaxies around the Milky Way. Since 2005, a dozen new satellite galaxies have been found around the Milky Way from SDSS data catalogue. They have an extremely small number of stars, and are the smallest galaxies known. By using wide-filed optical imaging data, I have determined how the stars are distributed inside the galaxies, and established that these galaxies only have extremely old stars.
