Trekipedia

Star, Type-F

White star. Temperatures ranged from 6000 to 7500°K. F-Type stars were composed of hydrogen and ionized metals, as well as calcium and iron.

Each spectral class (O, B, A, F, G, K, M) was divided into 10 subclasses, ranging from 0 (hottest) to 9 (coolest). Stars were also divided into six categories according to luminosity: Ia (most luminous supergiants), Ib (less luminous supergiants), II (luminous giants), III (normal giants), IV (subgiants), and V (main sequence and dwarfs). For instance, Sol was classified as G2V, which meant that it was a relatively hot G-Type main sequence star. In addtion, classes R, N, S, T, Q, and W were used for relatively rare star types not found on the main sequence.^[1]