![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Open_cluster_HR_diagram_ages.gif/640px-Open_cluster_HR_diagram_ages.gif&w=640&q=50)
Main sequence turnoff
From Wikipedia, the free encyclopedia
The turnoff point for a star refers to the point on the Hertzsprung–Russell diagram where it leaves the main sequence after its main fuel is exhausted – the main sequence turnoff.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Open_cluster_HR_diagram_ages.gif/320px-Open_cluster_HR_diagram_ages.gif)
By plotting the turnoff points of individual stars in a star cluster one can estimate the cluster's age.