Using the Hubble Space Telescope, Dr. Durrell and Dr. Feldmeier are part of a 13 member international team of scientists that have taken a 37-orbit exposure near the center of the Virgo Cluster of galaxies. The goal here was to measure the properties of intracluster red giant stars through the imaging. By a lucky coincidence, a small dwarf galaxy was discovered in the field (seen on the left), offering the first chance to study the stellar population of a dwarf galaxy in a galaxy cluster.
Planetary Nebulae are an ending phase of a star's life, where they become very bright in just a narrow emission lines of specific colors. This makes them relatively easy to detect and study. Once they are found, extragalactic planetary nebulae can help find the distances to nearby galaxies, and to measure the velocities of stars around galaxies. On the left is an image of the famous galaxy pair M51. The colored points refer to planetary nebulae whose radial velocities have been measured. A tidal "tail" of planetaries can be seen as the red and oranges structure on the upper left side of this image.
Some stars are not formed in galaxies, but are instead formed of the gas removed from galaxies. On the left here is an image of a part of the galaxy M81, as seen in neutral Hydrogen gas (the grey map). On top of them, shown as the blue points, are very young stars. Some of these, in the features labeled DW1 and DW2, are believed to be "infant" galaxies.