The gnome-core rpm contains several .desktop files corresponding to X applications (e.g., /usr/share/gnome/apps/Applications/XEphem.desktop) which are not part of the base system (and hence are likely not present). They should me moved to the rpm providing the binary.
These .desktop files are provided to make apps show up that normally wouldn't because their .rpm packages don't have .desktop files or they are installed from source. They won't turn into menu items unless the executables are installed - no harm being done here.