![telescope image of a star cluster, which is surrounded by a blue haze](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2021/07/072221_LG-HT_star-age_feat.jpg?fit=1030%2C580&ssl=1)
Clusters of stars like this one, called NGC6405 or the Butterfly Cluster, formed all of their stars around the same time. That fact has helped astronomers figure out how old star clusters are. But finding the age of individual stars is much harder.
N.A. Sharp, Mark Hanna, REU program/NOIRLab/NSF, AURA