The Hubble Space Telescope has been used to obtain WFPC2 ( V,I ) photometry for a large sample of stars in the outer halo of the giant elliptical NGC 5128 , at a distance 4 Mpc beyond the Local Group .
The globular cluster N5128-C44 , at the center of the Planetary Camera field , is well enough resolved to permit the construction of a color-magnitude diagram ( CMD ) for it which covers the brightest two magnitudes of the giant branch .
The CMD is consistent with that of a normal old , moderately low-metallicity ( [ Fe/H ] \simeq - 1.3 ) globular cluster , distinctly more metal-poor than most of the field halo stars at the same projected location ( which average [ Fe/H ] \sim - 0.5 ) .
This is the most distant globular cluster in which direct color-magnitude photometry has been achieved to date , and the first one belonging to a giant E galaxy .