Colour–magnitude diagram of Eridanus 2 based on photometry of public HST data. Median errors in 2 mag ranges are indicated with the error bars on the left. The red lines are the extremes of the fitting isochrones from the MESA Isochrones & Stellar Tracks project, with ages of 7 and 9 Gyr and a metallicity of −2.4 dex. The red shaded area shows the broadened isochrone obtained by varying the metallicity within its 3-σ confidence interval. The pink line is a 12 Gyr isochrone, which is the age estimated by Crnojević et al. (2016). The axis ranges have been chosen to show the majority of the data in greater detail; some data fall outside these ranges and are therefore not visible.