  Images of resolved 5.9 keV electron tracks produced from $^{55}$Fe X-ray
interactions are presented for the first time using an optical readout time
projection chamber (TPC). The corresponding energy spectra are also shown, with
the FWHM energy resolution in the 30-40\% range depending on gas pressure and
gain. These tracks were produced in low pressure carbon tetrafluoride (CF$_4$)
gas, and imaged with a fast lens and low noise CCD camera system using the
secondary scintillation produced in GEM/THGEM amplification devices. The
GEM/THGEMs provided effective gas gains of $\gtrsim 2 \times 10^5$ in CF$_4$ at
low pressures in the 25-100 Torr range. The ability to resolve such low energy
particle tracks has important applications in dark matter and other rare event
searches, as well as in X-ray polarimetry. A practical application of the
optical signal from $^{55}$Fe is that it provides a tool for mapping the
detector gain spatial uniformity.
