You observed three different star clusters and found that the main-sequence turnoff stars in cluster 1 had spectral type A, the main-sequence turnoff stars in cluster 2 had spectral type B, and the main-sequence turnoff stars in cluster 3 had spectral type G. Which star cluster is the oldest?

A.) cluster 1

B.) It is impossible to determine their ages given only the spectral types

C.) cluster 2

D.) cluster 3

The answer is D, cluster 3

Explanation:

Firstly, we need to understand that star clusters are a group or category of stars bonding together through a form of gravitational force. Streamlining down to a G-type star cluster, A G-type cluster is mostly refereed to as the yellow dwarf and this is because an example of a G-type star cluster is the yellow sun and because it is assumed that the sun is the oldest star, cluster 3 is the relative answer.

Answer: Cluster 3 (D)

Explanation: Cluster 3 is the oldest and it could be the source from which cluster 2 and 3 got their spectral type from.