NGC 6426: Colour-Magnitude diagram and variable star population as indicators of metallicity, distance, and age
This study analyzed new photometric data for NGC 6426 to determine its physical properties using a colour-magnitude diagram (CMD) and variable star populations. By comparing observed data with theoretical models, researchers estimated the cluster's mean metallicity (-1.93), distance (21.78 kpc), and age (around 13.9+1.9 Gyr). The findings confirm NGC 6426 as one of the oldest and most metal-poor globular clusters in the Galaxy.